structural system for tall buildings(1)

. ,. ..:#: , ..;F , ' . . .

Structural syst.erns for ~ a l l ~ u i l d i n g s

Council on Tall Buildings and Urban Habitat

S p o n s o r i n g Soclel lcr Internntlonul Asrocintion for Bridge and S w c t u r a l Engineering (IABSE) American Society of Civil E n g i n e e n (ASCE) American Inrtitute o f Architects (AIA) American Planning Asrocintion (APA) Inerna l iona l Union of Architects (UIA) American Society o f Inleriar Designers (ASID) .z~......I:.,, ; ...,, .~; Jnpon S t r u c t u n l Consultono Arrociotlon (ISCA) ..:; :.~ Urban Lnnd Institute (ULI) International Fedemlion of lnlerior Dcs ignen ( I R )

The following identifier those firms m d orgmiwt ionr who provide fartheCouncil 's financivl s u p p o h

P a t r o n s A1 Rnyes Group. Kuwait Consolidnted C o n t m a o r r Internulional Co.. Athens Dnr Al-Hnndnsah '.Shnir & Panncrr." Amman D L F Univcrsnl Limited. Ncw Dclhi Zuhair Fnyez & Arrociales. Jeddvh Juros. B n i m & Bolles. N e w York Kuwait Foundmion for the Advonccmcnt of Sciences. Kuwait Shimizu Corpondon . Tokyo T h e T u r n e r Corpomtion. New Yark

Sponsors Europrofilc Tecom. Luxembourg Gcorge A. Fuller Co.. New York T.R. Hnmrah & Yeung Sdn. Bhd.. Sclangor HL-Technik A.G.. Munich Hong Kong Lnnd Group Lld.. Hong Kong Kone Elevators. Helsinki John A. Mnnin & Aaroc.. Inc.. L o r Angelcr Ahmad Mohnrrom. Cairo Walter P. Moore & Associates. Inc.. Hourton Nippon Slcel. Tokyo Otis E l e w l o r Co.. Forminglan O v e A m p Pmner rh ip . London P D M Strocnl Inc.. Slockton Leslie E. R o b c m o n Associatea. New York Snmrung Engineering Br Conrtruction Co. Lrd..Seoul Snud Consult, Riyadh Schindlcr Elevntor Corp.. Morrislown Siecor Corporntion. Hickory Tukenako Corporation, Tokyo Tishmon Conslruction Corporarion of N c w York, New York Ti ihman Speyer Properties. Ncw York W c i r k o p i & Pickwonh. N e w York Wing T a i Conrtmction &Engineering. Hong Kong Wong & Ouynng (HK) Lld.. Hong Kong

Donor5

American Bridge Co.. Pittsburgh O'Brien-Kreilrbcrg & A S T O C ~ ~ ~ ~ C I . In=.. American Iron and Slcel Institute. Pennrlukcn

\Vushington, D.C. R T K L Associates. Inc.. Bnltimore W.R. Grncc & Comp;my. Cambridge Skidmore. Ou,ingr & hlerrill. Chicogo Hnscko Corporaion. Tokyo Steen Con~ul tun t r Pty. Ltd., Singspore T h c Herrick Corp.. Pleasnnton Syiko & Hcnnery. lnc.. New York Hollundsche Belon Mnnlschappij BV, nornton-TomorcuilEngineer5. Ncw York

Rijswijk Werner Vosr & Ponncrr. Braunrchwcig Hong Kong Housing Autl~ori ly. Hong Kong Wong Hobach Luu Consulting Engineers. La5 lffland Kivvnvgh Waterbury. P.C.. New York Angcles

C a n l r i b u l o n

Office o f Irwin G. Cwlor . P.C., N e w York L i m ConsulU~tts . Inc.. Cambridge H.K. Cheng & Pnr tnen Ltd. Hung Kong Meinhnrdt Auslrnlin Pty. Ltd.. Melbourne Douglas Specinlist C o n u n c t o n Ltd.. Aldridgc Mclnhnrdl (HK) Ltd.. Hong Kong H n n Conrulwnt Grnup. Snntn Monica Mucrer Rutledge Consult ing Engincen. The G c o r g ~ Hymnn ConsWcl ion Co.. N e w York

Balhrsdn Oboynshi Corpomtion. T o k y o Ingenicurburo Mullcr Mnrl GmbH. Mnrl O T E P In~crnntional. SA. Mndrid Institute Su lwn lrknndnr. Johor Charles Ponkow Builders. Inc.. Alwdenn

INTEMAC. Madrid Projcst S A Emprecndimentos e Servicos J H S C o n s w e n o e Plnncjnmento Ltd.. Sno Tecnlcos. Rin d c Jnnc im

Pnulo P S M Inlernnllonnl. Chicago Johnson Fain a n d Per r im Asroc.. Los Angeler Skil l ing Ward Megnurson B n r b h i r c Inc.. T h e Kling-Lindquist P m c n h i p . Inc. Senltlc

Philadclphio Tooley & Company. L a s Angcles LeMessurier Conrultnntr Inc.. Cnmbridge Nobih Your re f and Arrocinlcr. Los Angelcs

C o n t r i b u t i n g Pnr t l c lponl r

Advnnccd Slructuml Concrplr. Danvcr Advicrburnu Voor Bouwwchnick BV. Amhcm Amcrirnn lwti~ute of Slecl Con.uu~Lion. Chicago Anglo Amcricnn Pmpcny Scrviccr (Ply1 Lld.. lohnn-

"&burg Archituaml Scrviccr Dcpl.. Hong Kong Alelici D'Architcctum, dc Genvnl, Genvnl ~uslnlinn lnstitulc olSlccl Conrwcdon, hlllronr Poinl B.C.V. Pmnctti S.r.1.. Miiono . ~ ~ ~ - w.S. Bcllowr conrtriction Corp.. Hourton Aificd Bcncrch & Co.. Chicngo Balro dc lrnovclr Err Sno Poulo. S.A.. Sno Poulo Bomhont & W a d Pty. Lld.. Spring Hill ~ ~ u ~ d ~ ~ n y c r Wind Tunnci Labornlory (U. Wcrr- cm Ontnriol. London

Bovir ~ i m i l i . London Bnndow & Johulon ArrociaLcr. Lor Angclcr Bmokc Hillier Porker. Hong Kong Buildings & Dan. S.A. Bwsrclr CBM Engincm Inc.. Houston Ccrmo* Pcerkn Pacnen. Inc.. Fon Coilinr CblA A r h i t u ~ & Enginecn. Sari luon Conrfnction Conwlung Lbonlor ) . Dallor Cmnr Fuhicu Door Cu.. Lnkc Bluff Cmnc & Arloriolcr Ply. Lld. Sydnr) Da(11 Lugdon & Evcnll. London DeSimonc. Ch~plin & Dohr)n Inc. Kc. York D O ~ A rlrlnc ~ ~ g l n r r n ~ ~ . ~ n r . scatllc Fujilnva lohns~n on1 A s ~ o c i l r r . Cnlcagn Cunrndgc l inltns k D n r ) Ply Ltd. Sldnc) Holn.5 Lundhcrg U'nrhlcr Inlcmolion~l. Nc* YvrA 1io)ok;i~x Ar$ocialcr. Lo, Anerlcr I l r ~ l l l ~ ) Buildtng$ lnlrrn:l8vnll In:. F ~ i d r i l l ~ l t m ~ ~ h . O h m & Klsrlboum. lnc . S 81, F i a n r 8 ~ ~ o lnlrrnaliond lmn k Slrrl Imlilutc. Brulrcl$ Irwin Iohnrlon nnd Ponncn. Sydncy Infoc~er. S.A.. Rio delnoeim I.A. loner Conruuction Co., Charlotic Kcsting Mnnn Iemigan RoacL. Lor Angclcr KPFF Conrulting Engineen. Scuulc Lcnd Lwre Dcrign Gmup Lld.. Sydncy

~ n n i n & Bmvo, inc.. Honolulu Monin.Middirhrook & Louic. Snn Fmncirco Enriquc Mmincr-Romcm. S.A.. Mexico Mitchell McForlane Brrnlnoli & Paonen Inll. LId..

Honk Kong Miuubirhi Erwlc Co..Ltd.. Tokyo Moh nnd Arrociau. inc..Tnipci Morrc Diesel Inlcmorionrl. Ncw York Mvlriplci ConrWclions (NSWI Pfy. Lid.. Sydncy Nihoasckkci. U.S.A., Ltd., Lor Angclcr NiWIcn Sckkci. Ltd.. Tokyo Norman Dirncy & Young. Brirhonc Pacific Adnr Dcvclopmenl Corp.. Lor Angclcr PcddlcThorp Aururlin Ply. Lld.. Brirhnnc PorkTowrr Gmup. New Yo* Ccror Pclii & Asrociolu. Ncw York Pcrkinr & Will. Chicngo Rnhulnn Zain Arrociacr. Kuolo LumDur RFB Consulting Arrhilcnr, lohunnuhurp Rnrrnunrrrr G m r ~ m m Cons Engrr.. PC. llru York E m r n Rod, & Sons lnd. lnc.. New Yoik - ~, Rovon Woll8~mr Dlr t r l & lruin 1°C. Gurlph Scp l lo t Sa io rcmnding (Sdnl Bhd, K ~ o l o Lumpur scrrrn S m : m r Gimi5 dc Encrnhon~ S A . Rlo dc lnncim

Scvcmd Asrociacr Conr. Engn.. New York SOBRENCO. S.A.. Rio dr Inncim south Africnn lnrtiatc of Srccl Conslrucdon. Johm-

ncrbvrg stccl Rcinlorrcmcnt lnrlilulc of Aurlrnlio. Sydncy STS Conrultnnu Lrd.. Nonhbmok Studio Find. Nova E Coslcilnni. Milnno Tnyior Thornson Whining Ply Lld. St. Lconordr B.A. Vrvnroulu & Asrociacr. Athenr VlPAC Encinrcn & Sricndru Lid. hlclhovmc Worgon Cbpmon Pmnrrr. S)uncy Wndl~nl.cr A?ro:irlrl. Nrw Yorl wond~.,d.cl,dc Con~.lurn,. ~ r r . Yolk

Other Books in the Tall Buildings and Urban Environment Series

Casf-in-Place Concrete in Tall Building Design and Constructio~t Cladding Building Design for Handicapped and Aged Persons Semi-Rigid Connecrions in Steel Frames Fire Sofery in TON Buildings Cold-Formed Steel in Toll Buildings

Systems and Concepts

Structural Systems for Tall Buildings


Committee 3

CONTRIBUTORS I . D . Berzrretf~ Joseph Bicnls Brian Coviil P.H. Dayo~~~nr~sa Eiji Frrk!ria~ro him B, Ki1,rzister Rpscard M. I;o~~,aicz)k Owerr bJanin Il'iliion! Afuibortnie Sciichi Ml,ra?lrofsll % Okoshi AR,r~ad Rolrirnian Tltonras Scararrgeiio Roben Si,m Richard Ton!asefri A. )'atnohi

Editorial Group

Ryszard M. Kowalczyk, Chairman Robert Sinn, Vice-chairman M a x B. Kilmister, Editor

McGtaw-Hill, Inc.

New York San Francisco Washington. D.C. Auckland Bogoti Caracas Lisbon London Madrid MexicoClty Milan

Montreal New Delhi San Juan Singapore sydney Tokyo Toronto

ACKNOWLEDGMENT OF CONTRIBUTIONS

This Monognph uar prepxed h j Commillcc 3 (Slmctuml Syrtcm5)of ihc Council onToll Buitdlngr and Urban Hnbitnt nr p ~ n of the Tali Building, and Urban Environment Series. Thc edtlonll gmup $bas R)szxd hf. Kowatcz)k, chairman; Rohen Sinn, ricc-chnirmln; and hlox B. Kiimister, editor.

Special ncknowledgmentir due more individuals whore n k u w ~ i p l s formedthe mjorconvibution UI the chapters in his volume. These individuals and the chnpters or sections lo which they conhibuled ore:

Chapter 1: Editorial Group Chapter 2: Editorinl Group Section 3.1: Editorial Group Scction 3.2: Brian Cnvill Section 4.1: Eiji Fukuzawn Section 4.1: Seiichi Murnmulsu Section 4.1: Ahmod Rohiminn Section 4.2: Owen Mnnin Sccdon 4.3: T. Okorhi

Project Dercriptionr were conuibuted by:

The Office of Irwin Cantor CBM Engineers, Inc. Ellisor and Tanner. Inc. Kajima Design, Inc. KingiGuinn Associates LcMessuricr Consulrunls. lnc. Leriie E. Roberlson Arnocintes Nihon Sekkei. Inc. Ovc Amp & Pamcn

Section 4.3: Thomu Scmngello Section 4.3: Richard Tomasetti Section 4.3: A. Yamoki Section 4.4: Editorial Group Section 4.5: Editorial Group Section 5.1: William Melbourne Secdon 5.2: 1. D. Bennettr Secdon 5.2: P. H. Doynwnnrn Chapter 6: Joseph Bums

Paulus. Sokolowski, and Snnor. Inc. Pcrkins and Will Roben Rorenwarser Asrocioter Sevemd Associnter Shimizu Corporation Skidmore. Owings and Merrill Skiliing Ward Magnurron Barkshire. Inc Thomton-Tomaretti Engineers Walter P. Moore and Asrocioter

COMMllTEE MEMBERS

Hcrben F. Adigun. Mir M. Ali. Luis Guillermo Aycardi. Prnbodh V. Bnnavnlkur. Bob A. Bcckner. Charles L. Bcckncr. George E. Brandow. John F. Bmtchie, Robcn J. Bmngmber. Yu D. By- chenkov. Peter W. Chen. Ching-Chum Chcm. Pave1 Cirek. Andrew Dnvidr. John DeBremoekcr, Dirk Dickc. Robcn 0. Disque. Richard Dziewolnki. Ehun Fang. Alexander W. Founleh. James G. Forbes. Roben I. Hanren. Roben D. Hnnsen. Toshihnm Hisatoku. Arne Johnson. Michael Kavyr- chine. Mnn B. Kiimirler (editor). GcnF. Konig. Ryszwd M. KowaIczyk (chairman). Juraj Korak. Monsieur G. Lacombe. Siegfried Liphardl. Miguel A. Mneiar-Rendon. Owen Mnrrin. Jaime Mn- son. N. G. Mutkov. Gerardo G. Mayor. Leonard R Middleton. Jaime Munoz-Duquc. Jacques Nasser. Anthony F. Nnrretta. Fujio Nirhikown. Alexis Ortapenko. Z. Powlowski. M. V. Parokhin. Peter Y. S. Pun. Wcmer Quoscbnnh. Govidan Rahulan. Anthony Fracis Roper. Sntwant S. Rihai. Leslie E. Robenson. Wolfgang Schurilcr. Duiliu Sfintesco. Robert Sinn (vice-chairman). Ramiro A. Sofronie. A. G. Sokolov. Euuro Suzuki. Bungaie S. Tnranalh. A. R. Tonkley. Kenneth W. Wan. Morden S. Yollcr. Nobih F. G. Yourrcf. Stefan Zucrek.

GROUP LEADERS

The committee on Structural Systems is part of GroupSC of the Council, "Systems and Concepts." The leaders are:

lamer G. Forbes. Chairman Joseph P. Coluco, Vice-Chairman

Henry J. Cownn. Editor

Foreword

This volume is one of a series o f Monographs prepared under the aegis o f the Council on Tal l Buildings and Urban Habitat, a series that is aimed a t documenting the state of the art o f the planning, design, conslruction, and operation of tall buildings as well as their interaction with the urban environmenL

T h e present series is built upon an original set of five Monographs published by the American Society of Civil Engineers, as follows:

Volume PC: Plnrming nrzd En~rironn~enral Crirerio for Toll Beildings Volume SC: Tall Building Sysrems ond Cortceprs Volunze CL: Tall Building Criteria nnd Loading Volume SB: Srrucrurol Design of Toll Sreel Btrildings Voltrme CB: Srmcrural Design of Tall Concrele and Mosorrry Buildings

Following the publication of a number of updates to these volumes, it was decided by the Steering Group o f the Council lo develop a new series. It would be based on the original effort but would focus more strongly on the individual topical committees rather than the groups. This would d o two things. It would free the Council committees from restraints as to length. Also it would permit material on a given topic to reach the public more quickly.

T h e result was the Toll Buildings and Urban Enr,iron~nenf series, being published by McGraw-Hill. Inc.. New York. T h e present Monograph joins s ixo thers , the first of which was reieased in 1992:

Cost-in-Place Concrere in Toll Building Design ond Consrrucrion Clodding Building Design for Handicapped ond Aged Persons Fire Safely in Tall Buildings Senxi-Rigid Connecrions in Steel Frornes Cold-Formed Sfeel in Tall Buildings

This parlicular Monograph was prepnrcd by the Council 's Committee 3. Strucmral Systems. I ts earlier treatment was n part of Volume SC. I t dealt with the many issues relating to tall building structural systems when it was published in 1980. T h e committee decided that a volume featuring cane studies of many of the most important buildings o f the lust two decades would provide professionals with some interesting comparisons of how and why structural systems were chosen. T h e result of the committee's cfforls is this Monograph. It provides case studies of tall buildings from Japan. the United States. Malaysia. Australia. New Zealand. Hong Kong. Spain, and Singa- pore. This unique international survey examines the myriad o f archirecturni. engineering, and construcdon issues that must be taken into account in designing tall buildtag structural systems.

Preface

Although tall buildings are generally considered to be a product of the modem indusui- alized world. inherent human desire to build skyward is nearly as old as human civi- lizntion. The ancient ovramids of Giza in Eevot, the Mavan temdes in Tikal. Guata- mala, and the Kuwb in lndia arcjust a-fiw erampl& eternaily benring witness to this instincL Skyscrapers in thc modcrn sense began to appear over a century ago; however, it was nnly after World War I1 that rapid urbani'ration and population growth created the need for the conswction of tall buildings.

The dominant impact of Llll buildings on urban landscapes has tended to invite con- trnvenv. o~ticularl; in cities with older historic structuris. The skvscraoer silhouette ... has transformed andshaped the skylines of many cities, thercby creGing ;he most cbrr- acteristic and symbolic lrstaments to thc cities' wealth and their inhabitants' collecti!,e

The ordinary observer recognizes the tall building primarily with respect to its exterior architectural enclosure. This is nnly natural, as when we consider the great pyra- mids of Eevot our overridine imaee is bf their characteristic sharre. It is o d v re&ntlv ~~~ -~ -, . - - that we have begun to realize the creativity and colossal effnn expended by these ancient people to erect these swcmres in the desert at that time. So it is with the modem skvscrao;r. The overall soatial form as well as the intricate deWiline of the claddine svs- - , ~. - - - tems are crucial in defining the architectural expression and in placing the tower within the overall urban environment. The aim of this Monograph, however, is to have a look under the outer covering of the building to reveal the stiuctural skeleton as well as to provide historical knowledge documenting the design and construction techniques used to realize these monuments in today's world.

This Monoeraoh is therefore dedicated to the structural systems for tall buildings: their evo~utinn~anh historical development as well as the variety of solutions engendered to allow the tower to be realized safely andcfliciently. As in the pas!, new nchievoments

.in material science. comouter-aided desien. and construction technology have opened . . - -. paths toward more sophisticated and elcgant swcturnl syslems for wll buildings. The rwctuml system organization chosen for a p d c u l a r project determines the fundamen- [at oropcnies of the aver;lll buiidinc. the behavior under imposed loads, its safety, and oftin mav have a drnmatic imoact on the architectural design. The intent of this volume , - is lo demonstrate the chmcteristic features of many outstanding syslem form5 while documenting the faclors leading lo their selection for projects aclually realized.

The swctural systems for high-rise buildings are constantly evolving and at no time can be described as a completed whole. Every month new buildings are being designed and created, new projects conceived, and new schemes applied. Nevcnheless, we hope it is worthwhile to present the current state of the M while being aware that progress in svstems develooment is oneoine. -

The planning for thts Monograph began soon after the decision u,nc made by the Council to expand the chapters of the original Monograph into separate volumes. The concept of a volume based-on a survey of some of the most innovative examples of tall building swctural systems conuibuted by leading engineers and design firms of the

xiv Preface

profession was conceived during the committee workship in Hong Kong in 1990. It was only after estnblishina the editorial lendershir, for the work that the volume began to takc form, will1 tlte scope and content of the book finallred. At this time a buildinf data form wns prepared for collecting thc most essential inform3tion concerning the structural design of the buildings included herdin. The surveys were initiated and the re. s ~ o n s e s c o m ~ i l e d bv Max filmister. This material reoresen& the core of the comoleled dook and the.vast mijority of the work. Bob Sinn then'assembled all of the "looseknds" of the compilation in the summer of 1993 in order to finish the completed volume in time for publication.

The ~ o n o g r a ~ h as a uhole is a product of extensive lenmtr,ork. Sincere thanks go to all ofthc conuibutors who offered their valuablc time to share thew cxperirncc with the readers. It Is around this information that the cnurc uork is construc[ed. W e hope that the information included may be presented lo a broad professional audience. This ex- change of information is one of the tenets of the Council and is in fact a condition for progress in the design of tall buildings.

Supporting information for Chapter 5 from Drs. B. 1. Vickery. 1. D. Holmes. and J. C. K. Cheung is gratefully acknowledged, as is the Australian Research Grants Com- mission for its suppon of the fundamental research.

As mentioned, we are aware that everyday Progress is made in the field of structurnl engineering for high-rise buildings. Thc comn~itlce is already thinking about expmdlng and updating this \,olume. \\'c urge all readers lo enrich and complement thia rrrrrk by writing the Council or ioining the commitke.

~ i n ~ ~ l l ~ . wc would like lochpress our appruui;!lion to Dr. Lynn Beedle, ulto encour- aged us to prepare this work and \rho ad\,ised and aupponed tltc efiori. \\'e dudicall: this book to him.

Robert Sirm Vice-Cltoimmn

Contents

1. In t roduct ion

1.1. Condensed Rererenccs/Bibliography

2. Classif icat ion of Tall Building S t ruc tu r a l S y s t e m s

2.1. Condenrcd RererenceJBibliogmphy

3. Tall Building Floor S y s t e m s

3.1. Composite Sleel Floor Systems 3.2. Presmssed and Porttcnrioned Concrete Floor Systems

Project Dereriptionr Melbourne Ccnuvl Lulh Hcndqumers Building Riverside Centcr Bourke Plncc Cenuvl P l m One

3.3. Condensed RefercncerlBibliogmphy

4.. Lateral Load Res is t ing S y s t e m s

4.1. Bnced Frnme and MomentRc;isting Frnme Sysrems Project Derertptions

Mar B. Kilmisrer Editor

S~nwn Bank ACTTower Kobc Portopin Hole1 Nanhi South Tower Hotel World Tmde Center KobeCommercc. Indusuy and Mvrriott M q u i r Hotel Taj Mnhnl Hotel Tokyo Marine Building Knmognwn Grand Tower

Shear Wall Syrlemr Project Dc.cipUonr

Mcmpolitnn Tower Embassy Suites Hotel Singapore Treasury Building 77 Wcrt Wuckcr Drive Casielden Ploce Twin 21 Majestic Building Telecorn Corporate Building

Trade Centcr

Contents Contents

4.3. Core nnd Outrigger Systems Project Daeriptions

Cityspire Chifley Tower One Liberly Place 17 Smle Sueel Figuema at Wilrhlm Four Allen Center Tmmp Tower Woterfmnt Place Two Pmdentinl Plnw 1999 Bmadwvy CilibnnkPloro

4.4. Tubulorsyslemr P r o j s l Descriptions: Frnmed Tuber

Amoco Building 181 West Madiron Sueet AT&T Corpamte Cenler Georgia Pacific 450 Lexington Avenue Mcllon Bank Sumitorno Life Insumnce Building Dewcy SquoreTou'er Monon international Nations Bank Coipante Center Bvnk One Center Cenml Ploro Hopewcll Ccnuc

Project Descriptions: T-cd Tuber Fml Inlemationol Building Onteric Center John Hancock Ccnter 780 Third Avenue Holel de las h e r

PI'ojffL Dereriptions: Bundled Tuber Sears Tower Rinlto Building N6E Building Cnmegie Hall Tower Allied BonkPloro

45. Hybrid Systems PmjeclDiscriptions

Ovcrreos Union Bonk Cenler Citicorp Ccnrer CcnTmrusl Center Columbia Seafirst Center First Bnnk Place Two Union Squorc Fis t Intersmte World Center Hong Kong Bank Headqumers

4.6. Condensed ReierencesiBibliogmphy

5. Special Topics

5.1. Designing lo Reduce Perceptible Wind-Induced Motions 5 2 Fire Prolection of Swctunl Elements 5.3. Condensed RcfemnccdBibliognphy

6. Systems for the Future

6.1. A~hiEhilecedTendencies 6.2. Slructural Tendencies 6.3. Other Tendencies

Project Descriptions Miglin-Beiller Tower Deurbom Ccnter Bnnkof thc SouthwertTowcr Shimiru Super High Rise

6.4. Condensed RclerenceslBibliogmphy

Current Ouestions, Problems, and Research Needs

Nomenclature

Glorrury Symbols Abbreviudonr Units

Contributors

Building lndex

Name lndex

Subject lndex

Structural Systems for Tall Buildings

Introduction

Smctural sys tem for tall buildings have undergone a dramatic evolution throughout the orevious decade and into the 1990s. Developments in structural system form and orgnnirntion h m e historically been realized as a rcsponse to as well as an impclus toward emerging architectural uends in high-rise building design. At thc time of publication of the initial Council Monograph Tnll Building Systems and Concepts in 1980. international style and modernist high-rise designs, chanclerized by prismalic, repcti- live verticnl geometries and flat-topped roofs, were predominant (Council on Tnll Buildings. Group SC 1980). The devclopmcnt of Lhc prototype tubular systems for lnll buildings was indeed predicated upon an ovcrall building form of constnnt or smoothly varying profile. A representative office building project from the period is shown in Rg . 1.1. The rigid discipline of the cxterior rower form has since becn rcplaccd in many cases by the highly articulated vcnical modulations of rhc building envclopc characleristic of eclrclic postmodern. deconslructivist, and nrohistorical high-risrexpressions (Rg. 1.2). This general disconlinuily and erosion of thc cxterior facade has led to a new generation of tall building struclural systems that respond lo the more flexible and idiosyncratic requirements of an increasingly varied architectural aesthetic. Innovntive swctural systems involving megaframes, interior super- diagonally braced h m e s , hybrid steel and high-strength concrete core and outrigger systems, artificially damped structures, and spine structures nre among the composi- tions which represent a step in the development of structural systems for high-rise buildings. This Monograph seeks to further the plncement of some of the most excit- ing and unique forms for today's tall building structures into the overall tall building system hierarchy.

One of the fundamental goals of the Council has been to continualiy develop a tall buildings dambase. The members of Committee SC-3, Structural Systems, decided that rather than being a collection of papers or a general survey of tall building structural systems, the Monogmph would be organized with respect to such a database-type format of structural and oroiect information on actual buildine oroiecu. The commit- . . -. . tee thererore requested detailed informarion from engineers in Lhe profession, regarding the structural design of some: of the most innovative high-rise projecrq throughout the world. An enthusiastic resoonse from the s l ~ ~ c t u r n l eneineerine communirvoro- . . vided very spucific engineering informntion such as wind nnd seismic Iondingz. dynamic propenics. materials, and systems for a wide range of intcrnalional high-rise oroiecls, both comoleted and in o&oosal staee. which i r e comoiled in this single &k. These compr;hensive data &e [he p r i m 5 focus of this ~ o n n ~ r n p h and should

1

2 Introduction [Chap. 1 I Chap. 11 3 I be of interest and value to practicing engineers and architects as well as other tall building enthusiasts.

This Monograph is organized into six chapters. A general introduction to the classification of tall building structural systems is found in Chapter 2. The section begins to define the parameters and characteristics for which tall building systems are evaluated. Tall building floor systems arc discussed in Chapter 3, which includes recent

Fic. 1.1 Ouolicr Onb Tuwcr. Chicuco. Illinois. Comnleted 1984. I C c ~ ~ , n r s ~ ~ : Skirln,oru O w i n ~ r & .. . . . .- " f ierr i l l . ) Rg. 1.3 NBC T O C C ~ , Chicago. Illinois, Cumplclcd 1991. (Cauncry: Skidruorr O t ~ i n ~ s S blerriil.1

4 Introduction [Chap. 1 . , . : , , ., 1 ' ;.!

developments in posttensioned concrete floor systems for high-rise construction in Australia. Structunl systems for tall buildings have historically been grouped with respect to their ability to resist lateral loads effectively. Therefore Chapter 4. "Lateral Load Resisting Systems." forms the core of the work, with system descriptions for nver 50 oroiects. The oroiects are arraneed within five basic subclassifications for lat- - - r~ - . - era1 load resistance with generally increasing efficiency and application for taller . ,.. buildines: braced frame and moment resisting frame systems, shear wall systems, core $$:$$8% 1. k and ouGigger systems, tubular systems, anhhybrid systems. Each subsection is pre-

'.

ceded by a general introduction outlining the system forms. limimtions, advantages, and applications. Chapter 5 discusses special topics in high-rise building structural systems. It presents infor!nation concerning the developing topics of wind-induced motions and fire protection of structural members in tall buildings. The concluding Chapter 6, in dealing with systems for the future, presents examples of projccts on the drawing board and proposals which represent innovative state-of-the-art structural designs for tall buildings.

Classification of Tall Building

Structural Systems

1.1 CONDENSED REFERENCES/BIBLIOGRAPHY

Council on Tall Buildings. Group SC 1980. Toll Btrilding Syrlerm ond Conceplr.

The Council definition of a tall building defines the unique nature of the high-rise project: "A building whose height creates different conditions in the desieo, construction. and use than those that exisi in common buildines of a cenain reeionand oeriod." For

u b

the practicing structural engineer, the cataloging of suuctuial systems for tall buildings has historically recognized the primary importance of the system to resist lateral loads. The ~roeression ofiateral load resisiineichemes from eiemental beam and column . assemblages toward the notion of an equivalent vertical cantilever is fundamental to any suuctunl systems methodology.

In 1965 Fazlur Khan (1966) recognized that this hierarchy of system forms could be roughly categorized with respect lo relative effectiveness in resisting lateral loads (Fig. 2.1). At one end of the spectrum are the moment resisting frames, which are efficient for buildings in the range of 20 to 30 stories; at the other end is the generation 01 tubular systems with high cantilever efficiency. With the endpoints defined, other systems were placed with the idea that the application of any panicular form is economical only over a limited range of building heights. The system charts were updated periodically as new systems were developed and improvemcnts in materials and analysis techniques evolved.

Alternatively, the classification process could be based on cenain engineering and systems criteria which define both the physical as well as the design aspects of the building:

Material

Steel

Concrcte

Composite

Gravity load resisting systems

Floor framing (beams, slabs)

Columns

Chap. 21 Classification of Structural Systems [Chap. 2

7 6 I

Trusses Foundations . Lateral load resisting systems

Walls Frames Trusses Diaphragms . Type and magnitude of lateral loads

Wind Seismic

Strcngth and serviceability rcquirements

Drift Acceleration Ductility

In 1984 the Council attempted to develop a rigorous methodology for the cataloging of tall buildings with respect to their structural systems (Falconer nnd Beedle. 1984). The classification scheme involves four distinct levels of framing-oriented division: primary Framing system, bracing subsystem. floor framing, and configuration

TYPE I I TYPE 11 I I TYPE Ill 1 ) TYPE IV I Fig. 2.1 Cornpuriron of rlruelurol syetcmr. (CTDUH, CrortpSC. 1980.1

and load transfer. These levels are further broken down into subgroups and discrete systems (Fig. 2.2). This format allows for the consistent and specific identification and documentation of tall buildings and their systems. the overriding goal being to achieve a comprehensive worldwide survey of the performonce of buildings in the hieh-rise environment ~~~ =~~ ~ ~ . - - ~

While any cataloging scheme must address the preeminent focus on lateral load resislance, the load-carrying function of the tall building subsystems is rarely indepen- dent. The most efficient high-rise systems fully engage vertical gravity load resisting elements in the lateral load subsystem in order lo reduce the overall structural premium for resisting lateral loads. Some degree of independence is generally recognized between thefloor fmnzing sjsrr,t!s and the loferal load rerisring qsrenzs, although the integration of these subassemblies into the overall structural organization is crucial.

LEVEL A

Framing systems

LEVEL B I I

framing subsystems I (XX) /

Building configuration and load transfer (XX YY 2)

Elevation

Fig. 2.2 Clvrrilicoliun of rlrurlurul syrlernr. (Folnl,ler rrnd Beedlr. 1984.1

8 Classification of Structural Systems [Chap. 2

This Monograph therefore divides the discuss~on of tall bu~ldtng smctural Systems 1 into the subsystems mentioned. I

2.1 CONDENSED REFERENCES/BBLIOGRAPHY

3 Falconer and Beedlc 1984. Clarrlficnr!on of Toll Bulldlng S),srem.

Tall Building Khnn 1966, oprlmtzo~lon O ~ B U L I ~ ~ ~ S:rucrurer

Floor Systems

3.1 COMPOSITE STEEL FLOOR SYSTEMS

Composite floor systems typically involve simply supported structural steel beams. joists, girders, or trusses linked via shear connectors with a concrete floor slab to form &I effective T-beam flexural member resisting primarily gravity loads. The versatility of the system results from the inherent strength of the concrete floor component in compression and the tensile seeneth and spannabiliw of the steel member. ~omoos i t e flw; system are advantageous because ofreduced material costs, reduced labor i u e to prefabrication, faster couslruction times, simple and repetitive connection details. reduced stiuctural depths and consequent efficient use of interstitial ceiline soace. and - . reduced building mass in zones of henvy scismic activity. The composite floor system slab element can be formed by a flat-soffit reinforced concrete slab, precast concrete planks or floor panels with or without a cast-in-place t o ~ ~ i n e slab. o r a metal steel .. - . deck, either composite or noncomposite (Fig. 3.i). When a composite floor framing membcr is combined with a composite metal deck and a concrete floor slab, an ex~cmely eff~cient system is formed. The composite action of the beam or truss elc- men1 is due to shear studs welded directly through the metal deck, whereas the composite action of the metal deck results fmm side embossments incorporated into the steel sheet profile. The slab and beam arrangement typical in composite floor systems pr* duces a rigid horizontal diaphragm, providing stability to the overall building system while distributing wind and seismic s h e m to the lateral load resisting system elements.

1 Composite Beams and Girders

Steel and concrete com~osi te beams mav be formed either bv com~letelv encasine a . . ~~

steel member in concrete, with the composite action depending on the natural bond caused by the chemical adhesion and mechanical friction between steel and concrete. or by connecting the concrete floor to the top flanee of the steel frnmine member throueh shear c&nectors (Fie. 3.1). The concrete-encased comoosite steelienm was - . - . ~~ - ~~~ ~

common prior lo the dcvclopment of sprayed-on ccmentitious and board or ball type fireproofing materials, which economically replaced the henvy formed concrete insulation on the steel beam. Todny the m o s ~ c o ~ m o n nrrangemmt found in composite

9

10 Tall Building Floor Systems [Chap. 3

floor systems is a rolled or built-up steel beam connected to a formed steel deck and concrete slab. The metal deck tvnicallv roans unshored between steel members while - - ~ ~~ -. . . also providing a uorking platlonn for steel erection. The met31 deck slab may be ori- enled parallel or perpendicular lo the compo>ite beam span and may ilself be either comoosite or noncomnosilr (form deck). F i ~ u r c 3 ? shows a typical office building . - . . floor that is framed in composite steel beams.

COMPOSITE BEAM wm FlAT

MFFlrRElNFORCW CONCRETESLAB

C O M P O S E BEAM wrm METAL DECK

A N 0 CONCRETE SLAB (RIBS PEAPENDICUldR~

Fig. 3.1 Comporite benm sjstems.

COMPOSEBEAM W m MEFALOECK

A N 0 CONCRETESLAB (RIBS PABALLEL)

Sect. 3.11 Cornposits Steel Floor Systems 11

In composite beam design. h e stress distribution at working loads across the comnosite section is shown schematicallv in Fie. 3.3. As the tor, flanee of h e steel section is . - normally quite near h e neutral axis and consequently lightly stressed, a number of built- up or hybrid composite beam schemes have been formulated in an attempt to use the structural steel material more efficiently (Fig. 3.4). Hybrid beams fabricated from ASTM A36 grade top flange steel and 345-MPn (50-hi)-yield bonom flange steel have been used. Also, built-up composire beam schemes or tnpered flange beams are possible. In all of these cases. however. the increased fabrication costs must be evaluated which lend lo offset the rclalivt: malerial efficiency. In addition. a rcl3tively wide and thick- gauge top flange must be provided for proprr and rffr.cli$,e shex slud isslallalion.

A n"smat& comnosik steel beam h& two fundamental disadvantapes over other - types of composite floor framing types. ( I ) The mcmbcr !nus1 bc designed for the maximum bending momenl near midspan and thus is oRcn undcrs!rrs,ud near h e sup-

Fig. 32 Three First Nntionol Plnm, Chicago, Illiooir, lyplcnl noor.

WORKING ULTIMATE LOADS LOAD

Fig. 3.3 Composite beam stress dirlribution.

I :>,i;~

12 Tall Building Floor Systems [Chap. 3 j ,. , . ~ ::,

pons, and (2) building-serviccs ductwork and piptng must pass beneath the beam, or the beam must be provided with web penc~rattons (normally reinforced with plates or ancles leadinc to hirher fabricatton costs) to allow access for this csui~ment For this - u - . . reason, a number of composite girder forms allowing the free passage af mechanical, ducts and related services through the depth of the girder have been developed. They' include tapered and dapped girders, castellated beams, and stub girder systems (Fig. 3.5). As the tapered girders are completely fabricated from plate elemenls or cut from rolled shapes, these composite members are frequently hybrid, with the top flange designed in lower-strength steel. Applications of tapered composite girders to office building construction are limited since the main mechanical duct loop normally runs through the center of the lease span rather than at each end. The castellated composite beam is formed from a single rolled wide-flange steel beam cut and then reassembled by welding with the resulting increased depth and hexagonal openings. These members are available in standard shapes by serial size and are quite common in the United Kingdom and the rest of Europe. Use in the United Stales is limited due to the increased fabrication cost and the fact that the standard castellated openings are not large enough to accommodate the large mechanical ductwork common in modern high-rise, large floor plate building construction common in the United States. The stub girder system involves the use of short sections of beam welded to the top flange of a continuous, heavier bottom girder member. Continuous transverse secondary beams and ducts pass through the openings formed by the beam stubs. This system has been used in many building projects, but generally requires a shored design with consequent construction cost premiums.

HYBRID C0MPOSITEBEb.M

BUILT-UP COMPOSm BEAM

ROLLED

TAPERED FLANOE BUILT-UP HYBRID COMPOSITEBEAM COMPOSm BEAM

Fig. 3.4 Buill-up and hybrid composite bcnms.

Sect. 3.11 Composite Steel Floor Systems 13

Succc$si~ll cnmpnwte hc:m ile.;ign T'LII.IIL.\ the c~nsider i~t io~t n i \.ilriol~< <cr\ic~.- ability ~*.os; >o;b ;IS I~rnn-tsr~tt (clsupl denc:ti~rns ;lnJ nuor vihr;dinns. 0 1 p3rticul;tr cunccrn is lltc iw.c oi pcrc~ptihility of n:cupaot-indursd tl~tnr r ~ h r ~ l ~ o n s . The rsln- lively l!i;lt II~.rur;ll ~ l i l l n c r ~ oi a1o.l nltnporilc noor fr;lming a)slr.m> rerulls ill rela- t i t c h lot. !ihralion :~!#,t>litndrc irnm 1r.losilory hcel-dlop d ~ ~ i l : l t ~ o n s and thcr:lore is effective in reducing perccptihility. Recent studies have shown that short 17.6 m (25 fi) and lcss] and rery lollg clcar-sp;ln 113.7 nl (45 St) and longer] cunlposile floor framine svstcnls ncriornl suite well and :!re rarely found to transmit annoying vibra- - . . . tions to the occup8tnts. Particular care is requircd for span conditions in thc (9.1- to 10.7-m) 130- to 35-ftl rangc. Anticip.atcd danlping provided by partitions which extend to the sl:lb cthovc. serviucs. ceiling constructiot~,and the structure itself are used in conjunctiott with htate-of-thc-;lrt prediction tllodels to evalue~e thc potential for pcr- ceptible noor i~ibrations.

2 Composi te Jo i s t s and Trusses

Preeneinccred nronrictnrv oncn-web lloor ioists. ioisl rirders. and fabricated noor = . . . . - trusses are viable composite memhcrs when combined with a concrete noor slab. The advanta~es of an opetl-wcb nour framing 5ystcm include increnscd spannabilily and stiffnus;due to 1he.decocr s~ructural den& =ncl case in nccomrnodatine electrical con- ~ ~ - duit. plumbing pipes. and heating and air-condilioninp ductwork. Open web systems do, however. carry :I picmiuln for itreprunling thc many. rcla~ively ihin, components of

............................................................ TAPERED

.-, ;. .-., 1 b c:';;;~ C5ZJ -J?C: .... .. - L..

....... ....?........ . .-... .................... .*., TAPERED 6 C",I~~~~TE

-..,. ? .. .. ......................... .......................... DAPPED .... a??+- V--=d '. " >. . . . . . <: ;-, 1

CASTELLATED

Lf4-Z

........ . . . . . . . . . . . . . . . . . .......... .,,.,, ., ." , I I I <.

't. -.* SYSTEM

Fig. 3.5 Nonprismulie enn~purilc girdur.5.


the member. Open-web steel joists have been used in composite action with flat-soffit concrete slabs and metal deck slabs supporting concrete fill with and without sheer conhectors. The desien for these svstems i s orimarilv based on manufacturers' test d313 , I s ~~p 'n-~veb steel jotbtb and joist girders nornlally are \paced relatively clusaly. rile full polenrial lor composite elilc~cncy is not rcalircd as conlpared to o1hr.r cunlpor- ite floo; systems. Composite design does provide quantifiableadvantages over "on- comoositc desien for oocn-web floor ioisls such as increased stiffness and ducdlitv.

b - - ~ ~~

Ruill-up labricatcd compo\ilu nonr trusses cumbinc m ~ t u r ~ a l ciilcicncy io rcln- lively long-span 3pplicntions svtlh rn;lxinlom f lea~h~l i ty fnr iscorporaung huildinz-ser- \,ic<r dusluork and oioina into tilu cellinr! caritv. The urufill: of the truss lorm alluhi, . . - - for large mechanical air ducts as well as other piping and electrical lines to pass through the openings formcd by the lriangularization of the web mcmbcrs. The increased depth of the comuosite truss svslcm over a standard rolled-shaoe comnosite beam system with building-scrvices dictwork and piping passing bclbw the'beam results in maximum material eificicncy and high flexural stilfness. Generally, composite floor trusses are considcrcd economically viable lor floor spans in excess of about 9 m (30 it). A iurtltcr requirement Tor noor truss systems is that the Framing Iny- out be uniform. resuldng in relatively few truss types, which can be readily built in the fabrication shop using a jig. Otherwise the high lcvcl of fabrication inherent in the floor truss assemblage Lends to ofissct the relative material eliicicncy. For this reason, composite floor truss systems are particularly nttractive in high-rise uiiice building applications where large open lcnsc spans are required and noor configurations arc generally repetitive over the ltcight of the building. Figure 3.6 shows an example of a project utilizing composite noor trusses as part of an o\,erall mixed steel and concrete building irante.

Anv trianaulated oocn-web form can be used lo define the reometrv o f the fabri- - - cated noor truss: however. the Warren w s s , with or without web verticals, is the one utilized most often (Fig. 3.7). Thc Warren truss without vcrdcals provides n maximum open-web area to acco&modate ducta,ork and piping. Vertical wdb membcrs added to the Warren truss or a Pratt truss geometry may be utilized when the unbraccd length of the compression chord is critical. Often a Vierendeel panel in thc low-shenr zone near the center of the span is incornorated into the truss confiruration to accommodate the main air-handling mechanical buct loop in office building applications. The spacing of the web members should bc chosen such that the free passage of ductwork and piping i s not inhibited while maintaining a reasonable como~css ion top-chord . - . unbraced lensth. On the other hand. the nnlle of the web diaeonalr should be made =~~ ~~ L~~~ ~

~ ~

relatively sha~low to reduce the number of members and associated joint \\-elding. This must be balanced by the fact that shallower web members result in loneer unbraced - lengths and higher member axial forces, often requiring connection gusset plates. thereby increasing iabrication costs and decreasing the clear area for ductwork and piping. A panel spacing of roughly two to three limes the truss depth is a good rule of thumb for orienting web diagonals. The floor truss configuration should be detailed such that any significant point loads are applied at truss panel points. A vertical web member may be introduced into the truss girder geometry Lo transfer these imposed shear loads into the truss svstcm.

A variety o i chord and web member cross sections may be utilized in building,up the floor truss geometry (sec Fig. 3.8). Chord mcmbers may be wide-flangc T or sin- - gle-angle sections to allow easy, direct connection of web mcmbers without gusset plates. Rectangular tubes o r double-angle s e ~ t i o n s are less commonly used chord members as they require gusset-plated connections. Web members are most often Ts o r single- or double-ancle sections welded directly Lo the chord T or angle stem.

~ ~

althouih tube sections lhive been used. The composiie floor truss system is &mpleted through the direct connection of the top chord flange to the concrete floor sl-b by

Sect. 3.21 Prestressed and Posttensioned Concrete Floor Systems 15

shear connectors. The most common floor system in building construction is a comoosite metal deck and concrete slab chosen based on fire seoaration and acoustical requiremenu spanning between composite floor trusses. The floor trusses are normally spaced such that the metal deck slab sonns as the concrete form between the trusses without requiring any additional shoring.

3.2 PRESTRESSED AND POSTTENSIONED CONCRETE FLOOR SYSTEMS

Prestressed floors are commooolnce in buildines throuehout the world. narticularlv in u . . low-rise SlNCtUreS such as parking garages and shopping centers. Precast pretensioned floor units have remained popular since the 1960s. and cast-in-place posttensioned concrete floors have eainedwfde acccotance since the mid 1970s -

Poslrensioncd floors have been widely uscd for high-rise office buildings in Aus- tralia since the cnrly 1980s. and there are examples in the United States, the most notable bcing 31 1 South W a c k r Drive, Chicago, which was the tallest concrete building in the world when completed.

EXTEA1OR STEEL C O U P O S ~ GR4VITI COLUMNS AIIb SPANDRELS

TYPICALCOMPOSrrE FLOOR TRUSS

Fig. 3.6 One North Fmnkiin, Chiengo. lllinoir.


7 General Considerations

High-rise oftice buildings usually have long-span floors to achieve the desirable column-free space, and the spans are usually noncontinuous between the core and the facade. To achieve long spans and still maintain acceptable deflections requires a deep floor system in steel or reinforced concrete. However, by adopting prestressed post-

mumm WARREN TRUSS

Fig. 3.7 Camporilc noor trusr geometries.

CHOilOB h u b l ~ l n g l e m Ree?.TUk R L U b

WEB MEMBERS IL.% IL %. ri,n IZX ,,-Tub.

Fig.3.8 Composite trurr romponcnleections.

I ' Sect. 3.21 Prestressed and Posttensioned Concrete Floor Systems 17

I tensioned concrete beams it is possible to achicve a shallow floor structure and still m~intain accepwble deflections witl~our the need for expensive prrcamhering.

Hirlt-risc residential buildin~s usunllv do nor require lona spans because column- free s b c e is not a selling point;the tenant or buyer ices the spice already subdivided by walls, which effectively hide the columns. Hence continuous spans can be achieved. Unlike office buildings, residential buildings do not as a rule have suspended ceilings-the ceiling may be just a sprayed h~gh-build coating on the slab soffit or a plasterboard ceilina on battens fixed to tbe slab soffit. Flat-plate floors are

1 therefore required and deflection control is an imponant design consideration. Where I the columns form a reasonably regular grid, prestressing can be very effective in mini-

mizing the slab thickness while at the same time controlling deflections. ~ l f h o u g h it is customary to use posttensioning for prestressed concrete high-rise

buildings, precast pretensioned concrete can be used and has been employed in some buildines described in this Monomph (Luth Building: Mnrriott Hotel, New York; Tai Mahal hotell. The maior disadvaitaee of nrecast oretensioned concrete floor beams or - . slabs is the cranage required to lift the heavy uniu along with the field-welded connections required for stability and diaphragm action. Precast prelensioned floor members . - are usually tied together by and made composite with a thin cast-in-place topping slab.

Floor posttensioned systems use either 12.7- or 15.2-mm (0.5- or 0.6-in.) high- streneth steel strand formed into tendons. The tendons can be either "unbonded," " where individual strands are greased and sheathed in plastic, or "bonded," where groups of four or five strands are placed inside flat metal ducts that are filled with Eement eroul after strcssina. On a worldwide basis, bonded systems are preferred in high-rise buildings becausithey have demonstrated better long-term du&bility than unbonded systems. Although unbonded systems used today have improved corrosion resistance compared to earlier systems, there is still a large number of older buildings that exhibit corrosion problems in their unbonded tendons. Another reason that bonded posttensioned systems nre preferred is that cutting tendons for renovations or demolition is both simpler and safer when the tendons are bonded to the concrete. Nevenheless, care musibe exercised as it is by no means unknown for tendons specified to be grouted to have had this vital operation omitted. In this aspect. good quality control is essential. Figure 3.9 illustrates a typical posttensioned floor using unbonded tendons, whereas Figs. 3.10 and 3.11 illustrate the construction of a typical posttensioned floor using bonded tendons.

The most common posttensioned systems are:

Posttensioned flat slabs and flat plates (Fig. 3.12) Posttensioned beams supporting posttensioned slabs (Fig. 3.13) Posttensioncd benms supporting reinforced concrete slabs (Fig. 3.14)

Currently with computer programs readily available to carry out cracked section analysis of prestressed concrete, it is normal to design for partial prestress where the concrete is assumed to be cracked at full desien workine food and untensioned steel - - comprises a significant portion of the total reinforcement. The partial prestress ratio (PPR) gives the degree of prestress

PPR = .--!&- + A,&,

whereA f is the cross section area of orestressed steel multiolied bv its vield shenath r- "2 . . -

and A J is the cross section are3 of normal rcinforccd sleel multiplied by its yisld , 8 ) stress A useful starling point in d:tarm!ning the amount uf prcstrcss rzqi~ircd is lo pro- ride culficicnt prestress lo lh313ncc oboul 15% of the self-weight of the nnor blrUclllrLI.

i i 18 Tall Building Floor Systems [Chap. 3 I Sect. 3.21 Prestressed and Posttensioned Concrete Floor Systems

l9 I ; ,: :

, i Untensioncd steel is then added to satisfy the ultimate limit state. (This will often result

in a PPR of about 0.6.) Deflections and shear capacity must also be checked: The span-to-depth ratio of a single-span noncontinuous floor beam will be about

25; for a continuous beam it will be about 28 and for a flat-plate beam about 45 for an

I / internal span and 40 for an end span.

! I Fig. 3.9 Typical porllcnrioncd noor wing unbondcd lendonr.

Fig. 3.10 Typiroi porllcnrioncd noor using bondcd lunduns.

In high-rise buildings it is preferable to avoid running floor beams into heavily reinforced perimeter columns for two reasons:

1. There are difficulties in accommodating tendon anchorages, which compete far space with the column reinforcement.

2. Frame action developed between the beams and columns causes the design bending moment between floors to vary as the f ram~s resist lateral load, thereby diminishing the number of identical floors that can be designed, delailed. and conswcted.

Instead of being directly supponed by columns, the floor beams should be supported by the spandrel beams.

Prestressing anchorages can be on the outside of the building (requiring external access). at a step in the soffit of the beams [see Riverside Centre and Bourke Place (Figs. 3.15. 3.30, and 3.33)], or in a pocket at the lop of the floor. Top-of-floor pockets have the disadvantage that they usually cause local vnrialions in the flatness o i the floor and rough patches, which may need to be ground flush.

Bccause posttensioning causes axial shortening of the prestressed member, it is necessary to consider the effects of axial reslraint, that is, the effects of stiff columns

SRESSING

~ i g . 3.11 Construction requcnce I

GROUTING

br bondcd purttrnrionud conercle.


and walls. Such restraint has two potential effects: it can overstress the co!umns or walls in bending and shear, and it can reduce the amount of prestress in the floor.

Fortunately the stiff core of a high-rise building is usually fairly central so that the axial shortening of the floor can be generally in a direction toward the core. This means that the perimeter columns move inward, but because they move by the same amount from story to story, no significant permanent bending stresser occur except in ..., the first story abuus a nonprestressed,floor, which is often the ground floor. As this*:' ,lev is usually higher than a typical ,tory. the flexibility of rhc columns is greater and 1111: induced bdndinp mo~nents [nay be easily accommodated. Horvevsr. the loss of prc- stress in thc floor may necessitate some additional t~nte~~sioned reinforcement.

2 Economics of Posttensioning

Posttensioned concrete floors will usually result in economics in the total construction cost because of the following:

. Less concrete used because of shallower floor Structure (Fig. 3.16) . Less load on columns and footings . Shallower structural depth, resulting in rcduced story height (Fig. 3.17)

no drop panels

11 Multispan, flat plate, l r o ~ panels II

.:~. ..3)> ~:?* .

'2 , Sect. 3.21 Prestressed and Posnensioned Concrete Floor Systems 21

The last item can be very significant as any height reduction translates directly into savings in all vertical structural, architectural, and building-services elements.

The construction will proceed wilh the same speed as a normal reinforced concrete floor, with four-day floor-to-floor construction cycles being achieved regularly on high-rise office buildings with posttensioned floors (Fig. 3.18). Three-day cycles can easily,..be achieved using an additional set of forms and higher strength concretes to shorteb posttensioning time.

A major cost variable in posuensioned floors is the leneth of the tendons. Short ~

tendons ;re relativsly expen\c\,e compared lo long tendons. &re 3.1'1 shows tltc cost trend for tendons ranging front 10 to 60 m (33 to 200 it). Tlte relntively high cost of short tendons rssults from fixcd-cost components such as setup costs, asohorapcj, and lcndon stressing being prorated over lesser amo~nts of itrand. Tlte influence of strmd "retli~tg losses" is also greater with ruv shun strands, thus incrc3sing the area of tendon required. Nevertheless, even though most tendons in a high-rise building floor will be only around 10 to 15 m (33 to 50 it), the system is economical because of savings in floor depth, and it is desirable because of control of deflections and the lack of need for precambering. For grouted tendons. the optimum economical size has been

,, .~ round to be the four- or five-strand tendon in a flat duct because the anchorages are compact and readily accommodated within normal building members and because stressing is carried out with a lightjack easily handled by one person.


Comparing the cost of bonded and unbonded tendons will generally show the unbonded system as being slightly cheaper. This is because unbonded posttensioning usually requires less strand due to lower friction and greater available drape. Unbonded strand also does not need grouting with its costs of time and labor. As a floor using unbonded strand will require more reinforcement than a bonded system due to lower ultimate flexural strength and code requiremcnls, the combined cost of the strand and untensioned reinforcement will be almost the same as that for bonded systems.

The cost of a posttensioned system is funher affected by the building floor geometry and irregularities. For example:

The higher the perimeter-to-area ratio, the higher the normal reinforcement content since reinforcement in the perimeter can be a significant percentage of the lolal. . Angled perimeters increase reinlorcement and make anchorage pockets larger and more difficult lo form. Inlernal stressing from the floor surface increases costs due to the provision of the wedge-shaped stressing pockes and increased amounts of reinforcement. Slab steps and penetrations will increase posttensioning costs if they decrease the length of tendons.

1 , Ssct. 3.21 Prestressed and Posttensioned Concrete Floor Systems 23

Fig. 3.15 Bourkc Ploce. Melbourne, Aurlmlin: 53 levels.

Tall Building Floor Systems [Chap. 3 Sec t 3.21

3 Cutting Prestressed Tendons I One of the main drawbacks of posttensioned systems is the difficulty of dealing with stressed strands and tendons during structure modifications or demolition. Although modifications are more difficult, some procedures have been developed to make this . ,.. .,.: process easier. ,~-r...;.,., : .:,?$ .

Small penetrations required to meet changes lo plumbing or similar requirernenls !y::'J.-c: --2. -~ . .

are the most common of a11 modiiications that are made to the floor system. The size ' 1 ! of lhcse penetrations is typically from 50 to 250 mm (2 lo 10 in.) in~dinmeter. As a posrlenrioned floor relies on the posttcnsioncd tendons for IS strcnglh, it is prufrrablc to avoid cuttine, the tendons whcn drilling through the floor for the new penetrat~on. 1 Finding the tendons in a floor to permil the localbn of penetrations without damaging any tendons is a very simple procedure that is carried out with the aid of an electronic tendon locater. Tendons are accurately located using this system withon1 any need to remove floor coverings or ceilings.

Concrete Reinf + P.T.

Bl3.C. R P.T. Fig. 3.16 hlnteriul hnndling-reinforced concrete versus portlcnrioncd ryrlem.

Fig. 3.17 Exnmplc orstepped beurn sullil; Bourkc Plucc, hlclbourne. Aurlrnlln.

Prestressed and Posttensioned Concrete Floor Systems 25

Floor being poured7

Full access for Finishing Trades + 1

Fig. 3.18 Typlcnl noor propping.

Average tendon length, rn Fig. 3.19 Portlenrianing corb.


In a typical posttensioned floor it is possible.to locate penetrations of up to 1000 by 3000 mm (3 by 9 ft) belween posttensioned tendons and to require no other modifica- tion to the floor. Penetrations that require cutting of the posttensioned tendons will need lo be checked and designed as would any large penetration in any floor system. The procedure commonly adopted in a floor using bonded tendons is as follows:

1. Design the modified floor smcture in the vicinity of the penetration, assuming that any cut posttensioned tendons are dead-ended at the penetration.

2. Install any strengthening required. 3. Locate tendons and inspect grouting. 4. If there is no doubt as to the quality of the grouting, proceed lo step 5. Other-

wise strip off ducting, clean out grout, nnd epoxy grout the strands over a length of 500 mm (20 in.) immediately adjacent to the penetration.

5. Install props. 6. Core drill the corners of the penetration to eliminate the nced for overcutling.

and then cut the perimeter using a diamond saw. 7. Cut up the slab and remove.

8. Paint an epoxy-protective coating over the ends o i the strands to pre\,enl corrosion.

9. Remove props.

If a large penetration through a floor cannot be located within the slab area but must intersect a primary support beam, then substantial strengthening of adjacent beams will usually be necessary.

Whcn culling openings into floors built using unbondcd postlensioned tendons the procedures used for bonded posttensioned tendons cannot bc applied. The preferred procedure that has been developed to permit controlled cuttinf of unbondcd strands is

i to use a special detensioning jack. The jack grips the strand and the strand is then cut. with the force in the strands being released slowly. New anchorages are then installed at each side of the new opening and the strands restressed.

Extensive experience has been gained in demolition procedures for posllensioncd floors, and some general comments can be made. In bonded systems the procedures for demolition are the same as for reinforced concrete. The individual strands will not

! dislodge at stressing anchorages. In unbonded systems the strand capacity is lost over its entire length when cut; therefore the floor will require backpropping during demolition. The individual cut strands will dislodge at stressing anchorages, but will move generally less than 450 mm (18 in.). However, precautions should al!i~ays be taken in case the strands move more than this.

Project Descriptions 27 ,,. .

I PROJECT DESCRIPTIONS

I Melbourne Central Melbourne, Australia

.:, .. ., . .<. Architect

..I,

Structural engineer Year of compleIion He~ght from street to roof

Number of stories Number of levels below ground Bullding use

Frame maanal Typical floor live load

Basic wind velocity Maximum lateral deflcction

Design fundamental per~od

Design accelcrat~on

Dcs~gn damping Earthquake loading

Type of structure

Foundation conditions

Footing type Typical floor

Story height Beam span Beam depth Beam spacing Slab

Columns Size at ground floor Spacing Concrete strength

Core Shear walls Thickness at ground flool

Kisho Kurokswa with Bates Smar t & McCutcheon

Connell Wagner 1991

21 1 m (692 ft) 5 4

3 Office Concrete core, steel floor beams 3-kPa (60-ps0 beams, 4-kPa (80-psf)

slabs 5 0 m/s (112 mph) ullimate. 100-yr return

100 mm (4 in.), 50-yr rctum 4.2 scc

2.9 mg rms. 5-yr return 1% serviceability, 5% ultimate

Not applicable

Concrete core, concrete perimeter tube in lube

Mudstone, 2000-kPa (20-tonlfl') capacity Pads to columns, raft to core

3.85 m (12 ft 7 in.) 11.5 m (37 ft 9 in.) 530 mm (21 in.) 3 m ( l 0 it) 120 mm (4.75 in.) on metal deck

65 MPa (10,000 psi) maximum 600 and 200 mm (24 and 8 in.)

Melbourne Central comprises a 57-level office tower of 60,000 m' (646,000 fl') (net rentable) and a large retail development of a funher 60.000 m' (Fig. 3.20). The overall dimensions of !he tower are 43.72 by 43.72 m (143 by 143 ft). The tower is 21 1 m (692 ft) above street level and 225 m (738 ft) above the core raR. The facade is a glass and aluminum curtain wall.

28 Tall Building Floor Systems [Chap. 3 .. ,, Project Descriptions 29

" . I The lower floors consist of steel bums spanning from the core to the facade wi

composite concrete slab. supported on stoctural steel decking, spanning brtwecn steel beams (Fig. 3.21). The steel beams are generally at 3-m 1 10-it) centers. and typical beam is a 530UBB2 (21UB55). Tlie structural steel decking is I mm (0.04 thick, unpropped.

The column spacing at the facade is 6 m (20 ft). A perimeter beam is required to carry the intermediate floor beams. This is a 900-mrn-deep by 300-mm-wide (36- by 12-in.), prccasl concrete beam. Although this is precast concrete, it is erected in the same way as a sleel beam and as part of the steel frame. The use of precast concrete simplifies the fire rating of the slructure at the perimeter where access is difficult. It

. also provides the 900-mm (36-in.)-deep fire barrier between floors required by the building regulations. The fixings for the curtain wall are cast into lhis beam, resulting in reliable and accurate positioning.

The floor-to-floor height is 3875 mm (12 ft 8.5 in.) for the typical floors. The floor-to-ceiling height is 2900 rnm (9 ft 6 in.), which allows for a future access floor of 200 mm (8 in.) in height, to be installed by a tenant, providing a minimum 7700- mm 18-it 10-in.) occuoied soace.

~ i v wind resistance stricture for this buildine consists of the core cantileverine ~- " . from lhe lootin: in combinslion w i l l 1 3 nominal conlribulion from the filcndc rtruclurr. oi ihd column 2nd nrecnst bcnm. This ru,ulls in the fac3de structure cnrqing approximately 10% of the wind load on the building, and, more importantly, it convibutes

-

gig. 3.11 LOW-rirc floor LE-L14 hl~lbourne Ccnlml.


significantly to the sway serviceability perromance. The remainder of the wind load is carried by the core element.

The central-services core to the building is reinforced concrete from the footings to the roof. All the internal walls are 200 mm (8 in.) thick. This thickness remains unchanged over the full height of the building. The 200-mm (8-in.) internal wall thickness is h e optimum to achieve load-carrying capacity, minimal slenderness effects, and conslructability. The external walls vary from 600 and 550 mm (24 and 22 in.) thick at the bottom of the buildine to 250 mm (10 in.) thick at the buildine too. Concrete strengths in the core walls &y from 70 td 30 h&a (10.000 to 4300 psijat 9'0 days.

The columns are a composite of reinforced concrete with a 310UC137 steel column. These steel columns are erected as part o f the steel frame. Subseuuentlv thev arc encased within the reinforccd concrete column and oermit erection n i the sirel frame - ~ ~ - -~ ~ - ~ - - ~ ~

I0 floors J x a d ofconcrc.le cnc3semcn1 (RE 3 22). This conccpl, in comb!nolion wilh ~ h c rtci'l noor b u ~ n ~ s and rlructural aleel d:cking. pcrmils bun-fit in^ from 111c ~ d v a ~ l - tares of steel construction while at the same time minimizine the ouantitv of the rela- - - . lively cxpun<ive material t l~a t is sleel. This is iund3menlal lo 3 coniporile steel ind concrele buildine of this lype. where lhu advnnljges uf rctnforc~.d concrels 2nd s led are both incornorated into ihe strucmre.

The footings to the tower are foundcd in moderately weathered mudstone having a bearing capacity of 2000 Wa (20 tonlit'). The depth of the excavation and the basement i; such thnl the footines at the west end of the tower arc foundcd near the too of - this material. The footing lo the core is a 3.2-m (10-it 6-in.)-thick reinforced concrete raft. This extends approximately 2 m (6 ft 6 in.) past the outside face of the core wall.

Project Descriptions

MELEOURNE CENTRAL TLOm TO FLOOR O l l l E N Y O l 6

-- il r ~ ~ ~ n i nrrm firm

f P ~ E F ~ O ~ I C A T E O CSE LIR am R ) l , i l O l l O U ~ L D E ~ MI." ELECT m wut~eci T l t i ~ CAGE m nllil STEEL CDLUNII ARD LIFI ltim PJIIIIDII-!YITH STEEL CO.UI4N

PRCFLOR~UTED C~GE-' -t~n,io L ~ G A ~ U ~ ~ E L r l ~ o

FLMR STEEL BEAN

Rg. 3.22 noor-lo-floor dimcnri~nr and typical torer column reinrorccmcnt details; hlclbournc Ccntmi.


Luth Headquarters Building Kuala Lurnpur, Malaysia

Architect

S m c t u n l engineer Ycw of completion Height from slrcet to roof

Number of stories Number of levels below ground

Building use

Frame material Typical floor live load

Basic wind velocity Maximum lateral deflection

Design fundamental period

Design acceleration

Design damping Earthquake loading

Type of swclure Foundation conditions

Footing type

Tvnical floor . . Story height Beam span Beam depth Beam spacing Material Slab

Columns Size at ground floor Spacing Concrete slrenrlh

Hijjas Kasturi Associates

Ranhill BersekuN

1984 152 m (498 ft)

38 0 Offices, parking garage

Concrete

2.5 kPa (50 psfl

30 m/s (67 mph) Not available

Not eswblished Not established

Not established

Not applicable Tube in tube

Stiff silly clay 1500-mm (5-ft)-diameter bored piles.

20 m (60 ft) deep

3.66 m (12 ft) Varies from 19.2 to 8.7 m (64 to 28.5 ft) Typically 640 mm (25 in.) 9degrees radially Precast prelensioned concrete 100 mm (4-in.) precast planks, 50-mm

(2-in.) topping

5 by i.2 m (16.4 by 4 ft) 38 m (125 ft) around circumference 32 MPa (5000 psi) -

Core Reinforced slip-funned concrete

Thickness at ground floor 400 and 200 mm (16 and 8 in.) Concrete strength 32 MPa (5000 psi)

The Luth Headquarters Building is a 38-level office building in Kuala Lumpur (Fig. 3.23). Of the 38 levels. 37 are at or above ground and comprise 7 levels of parking garage, 2 mechanical-plant levels, and 28 levels of office space.

All floors are circular and contain a circular central core. However, in elevation the building is most unusual in that the facade is not vertical but formed from several solids of revolution. The facade of the lowest 22 levels is described by one circular


Fig. 3.23 Lulh Hcodqunrl~rr Building, Kunin Lurnpur, Mnioysin.


V Fig. 3.25 Tgpieul midrire noor plan; Luth Hcndquorters Building.

slrands


L 3 5 J Fig. 3.27 Core to noor henm joinl; Luth Hcndqunrlerr Building.

\4$12 500 4 Fig. 3.26 Typicill noor section; Lulh Hcildquorlcrs Building.

Tall Building Floor Systems

Fig. 318 Scclion of Lutb Hcndquorters Building.

. . :.,,.. 7: . . ,..

Riverside Center .,, . .

3'1 . , . Brisbane, Australia

Architect

Struclunl engineer Year of completion

Height from street to roof Number of stories

Number of fevels below ground Building use

Frame mnterial Typical floor live load Basic wind velocity

Maximum lateral deflection Design fundamental period Design damping

Earthquake loading

Type ofslructure Foundation conditions Footing type Typical floor

Story height Beam span Beam depth Beam spncing Material Slab

Columns Size at ground floor Spacing Concrete slrength


Harry Seidler & Associnter Rankine & Hill 1986 150 m (492 ft) 39 2 Office Concrete

4 kPa (80 psO

50 d s (112 mph) 63 mm (2.5 in.), 50-yr return 3.8 rec

2% serviceability, 5% ultimate Not applicable Tube in tube Rock, 5-MPa (56-todft') capacity

Pads to columns, mat to core

3.475 m (1 l f t 5 in.) 12 m (39 ft 4 in.) 600 mm (24 in.) 3.35 m (1 l ft) Posttensioned concrete 125 mm (5 in.) reinforced concrete

1100 by 700 mm (43 by 27 in.) 6.7 m (22 A) 50 to 32 MPa (7200 to 4500 psi)

Core Concrete shear walls Thickness at ground floor 350 and 200 mm (14 and 8 in.) Concrete strength 40 to 25 MPa (5700 lo 3500 psi)

This 39-story. 42-level building is a totally reinforced concrete slructure designed as a "tube in tube" (Fig. 3.29). However, because the triangular shape leads to unusually long exterior core wnlls. the core has a greater than normal stiffness, and the exterior spandrel beams and columns play only n minor role in the resistance to wind load (Fig. 3.30). The floors nre suppotled by simply supported partially prestressed beams spanning 12 m (40 ft) from core to perimeter. Slabs nre not prestressed.

Apart from the office building. the development includes a two-level basement garage, which covers the site and extends into the Brisbane River. The lowest floor is below normal high-tide levels, and the whole basement is designed to continue to function normally during a flood of a height resulting in a head of 6 m (20 11) of water at the lowest floor. The garage is topped by a ground-level plaza, low-rise commercial and retail buildings, and a restaurant which cantilevers 14 m (46 ft) o\,er the river.

Tall Building Floor Systems [Chap. 3 Project Descriptions

125 SLAB

8601 4W SPANDREL BEAM 7 XII SLAB

POCKETS IN CORE WALL

PRESTRESSING T E N D O N S ~ DUCTS I 4"- I

I ,LO,,

Fig. 3.29 Riverride Center, Brirbnnc, Auslrnlin. I

Fig. 330 Floor plnn; Riverride Cenler.


The ground conditions comprise hard phyllite. a metamorphosed mudstone, which allowed the use of design bearing pressures of 5000 kPa (50 tunlft'). Footings for the tower are reinforced concrete pads to columns and a raft slab to the core. The surrounding basement columns are supported on either pads or piers, depending on the rock level, which sloped away into the river.

Floor slabs are designed for a general live load o f 4 Wa (80 psf) with a 5-kPa (100- p s0 zone around the perimeter of thc core. The use of 4 kPa (80 psi) rather than the statutory 3 %Pa (60 psf) provides for the more ready accommodation of safes, isolated compacting units, and other heavy loads over a small area. The 125-mm (5-in.)-thick slabs span 3.3 m (10.8 ft) and are reinforced with fabric.

Floor beams are 600 mm (24 in.) deep nnd 350 mm (14 in.) wide at the soffit. (Sides are tapered to ease form removal.) At each end the beams terminate in a 300- mm (12-in.)-thick slab, leaving about a 1200-mm (4-ft)-wide zone in which to locate maior air distribution ducts. The prestressing tendons, of which there are two per . bsnm, usually four-strand. arc contained in uirculnr ducts, but anchored i n ilxb t)pc nnchongus. The s l h nochornpc> are the m o t econo,nicel and lend tbsmsulrss tu ibt uss of rm:lll. linht incks. Tlte circular ducts rdrult in o a r r a ~ e r bd i~ns cu~nparcd nlth the width required ior two flat slab ducts side by side.

The partially prcstresscd design provides for a load-balanced condition for about 80% of the weight of the bare concrete. This resulted in a flat floor. Ultimate load canacitv was orovided bv additional unlensioned steel. Untensioned steel stresses ~ ~ . ~, . ucrc limilcd to 130 hlP:, (?1.100 psi). Bcams were designed for lhe same l i \c lu:lds 3s

the slabs. chccpt th;tt rcduclions in 3ccurJancr. a!111 lllc luxling code a.r.rc urr.J. ,\I tach end ofth.: btnm. t ~ h ~ r l : i t b~comcs a \\id< 300-mm (I?-i,l ).deep slnb, cnnsid-

urjble anal)sis eifon *;is undsnaksn to ensure s3ttsf3ctu~ stress IL.VCIS. Ilcrc rdirliorie- lment is predomtnantly untcnsioncd slecl. wilh onl) otle of the tendons uontin.!iltg trl Ihc suooonine s~andre l beam: the other tendon terminates in a stressing anchorage at the end .. - . uf the 6UO-mm (2-i-in.).dcep rection of the bdnnl. This a r n ~ l g e m t ~ ~ o i tendons pr0vtdi.J for strtssing off ihd floor bclow-there nerd no externdl scnffulding r?quiremcnts.

Strcssinn was carried out in two stares: 50-c 3 da \ s niter puurinc ths slnb and 100% after? days. These requirements dictated the concrete strength &her than the minimum design strength specified. [The concrete yielded a strength of about 35 MPa (5000 psi) at 28 days. with 25 MPa (3500 psi) having been specified.] A prop load analysis was curried out, tnking into account the load-relieving effect of the prestress. in order to arrive at lhc time when props could be removcd.

Plant-room beams support a much heavier load than office floor beams, but the same floor formwork could be utilized bv increasinn the slab thickness and o\'erall - beam depth and by sloping the floor surface upward from the midspan of the beams. (The slab had to be thicker for ocoustic reasons anyway, and a fall for drainage was always required, so the structural requirements matched the other requirements.)

The service care has concrete walls. eenerallv 200 mm (8 in.) thick. exceot far the ...- ~-~ ~ - ~-~~ . . . . perimeter walls. alli;h wry from 350 to 300 tu 250 tnm ( l a in. lo I2 td I0 in.). Some tension in the lowcr rtonc5 occurs under dcsien wind Inads, but in ccncrnl loids ars comprcssion. Concrete was pumped for the full 150-m (492-11) height, with strengths varying from 40 to 25 MPa (5700 to 3500 psi).

An architectural limit was ulaced on the column sizes, resulting in thc use of 50- . MPa (7100-psi) concrete and 4% reinforccmcnt at the lower levels. Some carly problems were encountered with misplaced bars, which made the placing of spandrel beam reinforcement very difficult, particularly as the column bars w e e 36 mm (1.4 in.) in dinmcter and in bundles of up to four bars, but once a stccl template was employed to locate the bars. the problems disappeared. Where bundled bars were used, all column bars were specified io have splicing sleeves.

I Bourke Place Melbourne, Australia

Architect

Structural engineer Year of completion Height from street to roof

Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity

Maximum lateral deflcction

Design fundamental period Design acceleration

Design damping Earthquake loading Type of structure

Foundation condttions F o ~ t i n g type

Typical floor Story height Beam span Beam depth Beam spacing Material Slabs

Columns Size at ground floor Spacing Concrete strength

Core Thlchness at ground floor Concrete svength


Godfrey & Spowers

Connell Wagner

1991 223 m (732 ft) 5 4 3 Office Concrete 4 kPa (SO psf) 39 m/s (87 mph), 50-yr return

200 mm (8 in.). 50-yr return

4.8 sec 3.7 mg rms. 5-yr return 1% serviceability, 5% ultimate

Not applicable Reinforced concrete core and perimeter

frame tube-in-tube Highly weathcrcd siltstone

Pads to columns, raft to core

3.7 m (12 it 2 in.) 10.8 m (35 f t 5 in.) 400 mm (16 in.) 4.6 m (15 ft) Posuensioned concrete 125-mm (5-in.) reinforced concrete

1 I00 mm (43 in.) square 8.1 m (26 ft 6 in.) 60 MPn (8500 psi) maximum Slip-formed shear walls 400 and 200 mm (16 and a n . ) 60 MPa (8500 psi) maximum

The Bourke Place project includes a lower structure with 5 4 floors above Bourke Street in the city of Melbourne (Fig. 3.31). On top of the concrete tower is a steel- framed, aluminum-clad cone roof reaching another four stories and a communications tower rising to approximately 255 m (837 ft) above the street. Alongside the tower there are an 8-storv narkine raraee (four of which are below eround) and olazas with , . - - b , .. . . rood and retail areas. The total leasable floor space in the office tower i s approximately 60,500 m' (651.200 ft').

The tower structure consists of a slip-formed reinforced concrete core, posttensioned concrete band beams, and a reinforced concrete perimeter frame (Figs. 3.32

44 Tall Building Floor Systems [Chap. 3 Project Descriptions 45

and 3.33). The core structure is approximately 20 m (66 ft) square at the base. Most internal walls are 200 mm (8 in.) thick. with some 150 mm (6 in.). and remain constant for the full height of the structure. The external wails vary from primarily 400 mm (16 in.) thick at the base. using 60-MPa (8500-psi) concrete. to 200 mm (8 in.) lor the top 15 slories, requiring only 25-MPa (3500-psi) concrete [40 MPa (5500 psi) was used for pumpability.] The use of high-strength 60-MPa (8500-psi) concrete allowed the wail thicknesses

to be minimized. It wns estimated that the loss of floor space for thicker walls, if40-

Fig. 3.31 Bourke Piore, hlelbourne, Autrniin. (Plioro by Srjl~irc Plio!ogropi!ic.r.)

Fig. 3.32 Typical tower floor plon; Bourke Place.

? O R ivn,oxn ,m "liiiill ilC DiiYI*i

Fig. 333 Typicill noor profile, ~ o u r k e ~ i u c c .


MPa (5500-psi) concrete was used, represented an effective extra ovcmll capitalized cost to the client of approximately $;100,000 (Australian) per floor.

Two substantial core shape changes occur up in the tower as elevator shafts that service the lower levels become redundant. The location of these shaoe changes and - the changes in wall thickness were positioned sufficiently high up in the tower to ensure that the cote aould be off the construction crilical path in order to avoid any time delays. The design of the slip form incorporated the facility to reduce the wall thickness and to "drop off' these portions. Cost comparisons during the design dcvel- opment phase indicated that slip forming was the most cost-efiicient method of construction, and the Bourke Place core was the largest single slip-formed core ever constructcd in Austmlia. The core conrtruction set an Australian record in Novemhcr

~ ~ ~

1989 lor pumping concrelc to 2 10131 risc of236 m (77.1 it). A t the tilne of dcs~gn, building rcgulations lor fire prolcc~inn required 1h3t spandrel

benms he a1 least 900 lllln (36 in ) d~wp. 11 ulas recoQnized that. In cunjunction with the columns, lllese beams svould therslore m?ke some contnbu~ion lo the oucrall resis- t2nce lo brnd In3d5 on lhc slnlcturc. Tnr h e ~ m s ucr? designed for l l~c dead and livc load requircmcnts: then their capacity to resist additional wind load was assessed. This amounkd to approximately 7.5% ofthe total wind load on the structure, meaning that the core need only be designed for 92.5% rather than the full wind load. The "core and partial-frame" approach represented significanl cost savings to the client.

A 125-mm (5-in.) normally reinforced concrete slab spans between 10.8-m (35.4- it)-long band beams at typically 4.6-rn (15-it) centers. The band beams radiate out from the core and are typically 400 mm (16 in.) deep, but are notchcd at each end to 275 mm (1 1 in.). The notches wcrc introduced to accommodate primary mechanical ducts, and they enable the total floor-lo-floor height to be minimized. This represents savings to the client as the overall height of the building can be reduced without aflectine, the number of Floors.

The band beams are posttensioned from underneath, utilizing the vertical face of the notches. This separates the posttensioning contractors from the "work hce." allo!vine stressine to be carried but indeoendent of scaffold erection on the newlv - - poured floor. nnd it r l i m i ~ ~ a ~ e s ihc n<<d Tor reccsssd pockets in the flour surlace.

T11c b~i ldcr used three seu oll;!ble fonns which "lclpfrog~ud" up tllc structure and dit,idcd the floor into four pours of appruxirnatcly 350 rn' (3800 it'), with 111s inten- riun or pouring one qul idr~n~ wcry dzy. To sssist in mli~ntninlng his &day cycle, column xnd bean^ reinforccn~~.nt cages \tJcre stmdardiz2d u,here possiblc and prefabrib c;11cd.

Tllc floor! ~ V C T ~ c11~~kcd 10 CnsUrL: 111.11 ~lnder llle l l l~s l f a v ~ r ~ b l ~ c~r~umsliinces 110

hack propping trould be necessary. Typically, Floor cyclcs of apprurimatuly -I lo 5 working dnys were acllieved


Central Plaza One Brisbane, Australia

Architect

Suuctural engineer Year of completion Height from sveet to roof


Building use Frame material

Typical floor live load Basic wind velocity Maximum lateral deflection


Design acceleration Earthquake loading Type of structure


Footing type

Typical floor Story height Slab

Columns Size at ground floor Spacing Concrete streneth

Dr. Kisho Knrokawa. Peddle Thorp Partnerships

Maunscll Pty. Ltd.

1988 174 m (571 ft) 44 4 Office

Concrete 3 P a (60 psO 49 d s (1 I 0 mph). 50-yr return

350 mm (13.75 in.), 25-yr return 4.4 and 3.8 sec 16 mg peak. 5-yr return

Not applicable Central core with perimeter framed tube

Marine clay over rock. 5-MPa (5-tonlfi') capacity

Spread footings, anchored perimeter wall

3.66 m (12 ft) 10-m (33-ft)-span posttensioned. 275 mm

(10.8 in.) thick

1200 by 1000 mm (47 by 39 in.) 7 m (23 fl) 50 MPa (7100 psi) -

Core Concrete shear walls Thickness at ground floor 600 and 250 mm (24 and 10 in.) Concrete strength 50 to 32 MPa (7100 to 4600 psi)

Central Plaza One is currently Brisbane's tallest building with a total of48 levels and has a total height of approximately 174 m (571 ft) above sveet level (Flg. 3.34).

The building features a four-story avium with an internal running stream and landscaping at the ground-floor level. and a four-level basement garage. A distinctive roof line with a lifting, slewing telescopic building maintenance unit forming the top 2.5 m (8 ft) of the roof structure makes the building unique among modem high-rise buildings in Australia. The tower houses three plant rooms at levels 4.26. and 41.

A six-story office block adjacent to the main tower has banking facilities at the ground-floor level and shares the common basement structure with the tower. ThlS "hank annex" incorporntes an additional plant room nt level 5.

Tall Building Floor Systems

The tower structure comprises a reinforced concrete core and frame with posttensioned floors and is founded on rock approximately 13 m (43 it) below street level. Design requirements were as follows:

Column-free office space requiring floors to span 10 m (33 ft) from perimeter beams to central core Floors to be designed to allow for maximum flexibility in locating penetrations for services

s Floor edgr beams to be designed and detatled to allow for variations at corners to range from 6-m (20-1'1) cantilevers to fully truncated corners A minimum number uf minimum-size columns up through t l ~ c atrium and above togerhcr with the assurance that accclerat~ons due to wind-rxcitcd oscillations be within acceptable human response lirnitotions

Fig. 3.34 Central Pinzn One, Brisbnne, Aurtmlin.


. An accurate assessment of deformations due to creep, shrinkage, and load effects to allow for joint design at critical locations in the curtain-wall system

m A bosement structure to accommodate 270 cars - A roof shucture to support a lifting, slewing. and telescoping building maintennnce unit

j$!. Preliminary analysis of the building using a simplified annlyticnl model indicated that the tower would be wind-sensitive and accelerations could be excessive. The simplified model comprised the central core as a cantilever linked to the outer frames, with axially stiff linkages representing the floors. the entire assemblage being considered as a plane frame. Having gained considerable insight into the behavior of the structure from the preliminary analysis, the tube-in-tube structural system was chosen for resistance to lateral wind loads.

During the preliminary design stage a l:400 aeroelastic model was being developed and tested in a wind tunnel to d e t e d n e and minimize wind pressures by varying the dvnamic earnmeters. Considerable analytical work was carried out to tune the

I ' *truckre aera~lasticallv. The stiffness and mass of various structural components were

I ~- ~ -~

adjusted nnd readj~rstcd in this process to minimize !he aeroelastic forces. Once the slructurai form was finalized. a rigorous three-dimensional tobc-in-tubc

1 .~n~lvclq was carried out. This was necessarv toensure that disolacements and acceler-

I ,- .- -~

ations under \vind 1o;ading were brlou acceptable Ie\,cls. In lhc analysis for core-frame interaction. the structure \\,as propped at the ground floor :,nd ;!I each of the basemrnt

I levclc qo hat lateral loads could be transferrid out to the site oerimeler walls throueh .. .- diaphragm action of the floor slabs. Propping of the structure'at the ground floor a id basements avoided the problem of having Lo deal with large momens at the core fool-

i I ing and also served to convol deflectioniand accelerations of the building under wind

j load. Of particular importance was the cross-wind response of the building, which produced a resulting ntoment 1.6 times the along-wind response.

The cenval core occupies a space approximately 16 m (52.5 ft) square in the center of the building and is, in reality, two cores with an elevator foyer space between. The two cores are linked together via floor slabs and beams, and in addition, by large diaphragms in the atrium and plant rooms. The atrium diaphragms were found to be particularly effective in reducing deflections by giving the building an exceptionally high point of rotation approximately 45 m (148 ft) above street level.

The central core is a multiccll reinforced concrete structure with wall thicknesses varying from 200 to 600 mm (8 to 24 in.). Reinforcement ratios vary from about 1% in the lower parts of the building to 0.5% at the top. The core was designed globally for biaxial bending and axial load using the program FAILSAFE. In this program a particular section of the core is defined as an assembly of square elements within a system of coordinates, and the quantity and location of steel is also defined within the coordinate system. The program outputs a failure surface for axial load versus moment.

A detailed dcsiyn of the core at licodcrs. coupling bu.lrns. xnd dii~phr~gnlb \+.IS Car- ried our using decp-hmm liicury, hear-fricuon theory, and cun\,r.ntion~l rdinC0rci.d concrete theory, as appropriate for the element under consideration.

Basement floors u.ere designed as conventional reinforced concrete flat slabs. except that two special effects required particular attention in the design and detailing of reinforcements, namely. (1) transfer of wind loads out of the core to the basement walls. and (2) differential settlement betwccn the core, maiar columns, and basement columnr. Pcrticulx :!ttention rrar paid to detailing the r~inforcunlentr at thc core-Sl:lh joints, both on lhc dm\r!ng board :!nd on rltc during cnnstruction.


The ground-floor slab was designed in reinforced concrete, incorpomting an extensive beam system. At this level the wind-propping loads were considerably higher than in the basement slabs, and in addition the slab was designed to support a 10-Wa (200-psO conswction live load to allow for scaffolding up to support level 4 plant- room slab over the atn'ltrn

~ ~

The ground-floor slab is a multilevel slab with sloping and stepped purtions, and in the nonheast comer it contained large openings. Special bands of heavy reinforcing steel were required around the perimeler to vansfer wind loads into perimeter walls. A diagonal band of heavy steel from the core to the northwest corner of the site was required lo ensure a load path to compensate for the large penetrations of the nonheast corner.

Tower floors were designed as posuensioned flat plates spanning approximately 10 m (33 ft) from the spandrel beams to the cenval core. Typical floor slabs are 275 mm (I I in.) thick and are stressed with tendons in bands of six, each tendon comprising five 12.7-mm (0.5-in.)-diameter supergrade strands in 90-mm (3.5-in.)-wide ducts. The banded tendon arrangement provides maximum flexibility of floor layout for the positioning of penebations for services and internal stairs in the tenancy design stage.

The flat-plate soffit was important in allowing the builder to speed up the formwork placing and in achieving the specified cycle times. Posttensioning also meant minlmum passive reinforcement, another feature to assist thc builder.

Finite-elemcnt analysis of the floor slab indicated the existence of high shear slresses near the comers of the core. This was dealt with by installing some shcar stccl locally in the slab near each corner of the core. Spandrel beams n8erc generally reinforced concrete, except for the longer cantilever bcams at the comers of the building, which were posttensioned to minimize deflections.


Kilmirrer 1983. Design and ConnnlcIia,r offl~e Lull? Heodqaunrrs Buiidirtg, K ~ o i o Lu,npur

Monin 1989, lVirzd Design ofFourBuiidirtgr up to 306 ,n TO!!. L'in*fistrin Irnliimn *el Cementa 1987. T/U Lurb Bsiidittg ir2 K ~ , ~ I O L~~~~~ ( ~ f ~ i ~ ~ ~ i ~ ~

Lateral Load Resisting Systems

* -,

.<.

-' 4.1 BRACED FRAME AND MOMENT RESISTING FRAME SYSTEMS

Two fundamental loteral force resisting systcms are the braced frame (also kno\\'n as shear truss or vcrtical truss) and the momcnl rcsisting frame (moment frame or rigid frame). Thesc systems evolved during the beginning of high-rise construction in the

twentieth century. Braced framcs and momcnl resisting frames are normally organized as planar assemblies in orthogonal directions to create ~ l a n a r framcs or a tube frame system. Thc two systems may be used together as an overall interactive SySlem. thereby their individual applications to taller buildings. Both systems arc commonly used today as effective means of resisting lateral forces in high-rise construction ior buildings of up to 40 or 50 stories.

I 1 Braced Frames , . . 1 !., Braced framcs arc cantilevered vertical trusses resisting lateral loads primarily through

I ' ? the mial stiffness of the frame members. Axial shortening and elongallon of the column

I memben under lateral loading accounts for 80 to 90% of the overall system deformation lor slender truss systcms. The effecriveness of the system, as characterized by a 1 h i ~ h ratio 01 stiffness to material quantity, is recognized lor multistory buildings in the

low- to midhcight range. Braced frame geometries are grouped, based on their ductility characlcristics. as

either concentric braced frames (CBF) or eccentric braced frames (EBF). In CBFs the axcs of all mcmbcrs intersect at a point such that the member forces are axial. CBFs have a great amount ofstiffncss but low ductility. Thus in areas of low seismic acr~vil)~. wllcre high ductility is not essential, CBFs arc the lirst choice or engineers for lalcral load resistance. EBFs. on the other band. utilize axis offsets to introduce flexure ,and shcar into the frame, which lowers the stiffness-to-weight ratio but increases ducttl~ty. The CBF can take the lorm of an X. Pmtt, diagonal, K. or V, as sho$\,n in Fig. 4. I .

The X bracings exhibit hizhcr lateral stiffness-to-\lzeigl~t r ~ l i o s in comparison to K OrV bracings. Ho\ree\'er, the X bracings crcnte a short circuil in the column gravity load

52 Lateral Load Resisting Systems [Chap. 4

lransfer path as they absorb a ponion of the column load in proportion to their stiffness. This creates additional forccs in both diagonal and horizontal members of X-bracing svstems which need to be considered in svstem derivn -.. =...

To accommodate door and other openings, EBFs are commonly used, a s shown in Fig. 4.2. The shear and flexural action caused by the axis offset in Ule link beam improves ductility. Higher ductility through inelastic shear or bending action of the link beam make it a desirable lateral system in areas of high seismic activity. Ductility is measured by a well-behaved hysteresis loop and achieved through proper connection and member design such that all modes of instabilities and brittle failures are eliminated.

Braced frames are most often made from structural steel because of ease of construction. Depending on the diagonal force, length, required stiffness, and clearances. the diagonal member in structural steel can be made of double angles, channels, tees. tubes, o r wide-flange shapes. Besides performance. the shape of the diagonal is often based on connection considerations. Examples of typical braced frame connections are depicted in Fig. 4.3.

Vertical trusses are often located in the elevator and service core areas of high-rise buildings, where frame diagonals may be enclosed within permanent walls. Braced frames can be joined to form closed section cells, which logetherare effective in resisting torsional forces. These cells may be bundled to take advantage of additional stiffness and provide a systematic means of dropping off the cclls at the upper levels of a

X-BRACING

...... /.. ,.. ::. ..

....... j.. ... 4 ::. ...

PRATT BRACING DIAGONAL

BRACING

K BRACING KNEE

V BRACING BRACING

Fig. 4.1 Concentric br;lrcd rromc rorms.

Sect. 4.11 Braced Frame and Moment Resisting Frame Systems 53

3;. lourr where laleral forces are reduced. The strength and stillness of the lruss syslcm is thus sensitive lo the lootprtnt of ihe core area and the arrangement 01 the clcvators.

When ihe slenderness ratio of a core truss (the ratio of truss height lo le2rt u,idth) In- . creases. the o,,emll overturning cffecl manifests il5:If in ~ncrcascd axid dclorn~ntion

and uolifr forces of chord columns. While truss chord members may rr3dily be drsigned forces, net foundation uplift forces are generally &desirable. A design be lo spread Lhe chords as far apart as possible while diverting gravity

load to these chords to Drevent or reduce the net tensile force. As slenderness increases. the a i a l drformalions of lllc chord columns o f a truss sys-

tem become more critical in controlling the sway of the slructurc. Increasing the r l~ l f - nrss and strsnath of lhe chord members in proponion lo the work done by those members will prov%e an effective way to minimiz; sway. The bracing system between the

.~ . chords can be designed to transfer the gravity loads of any intermediate chord columns

, to the boundary chord columns. As a result the intermediate chord columns could be eliminated or minimized in size and the efficiency of the boundary chords maximized.

To further reduce the steel tonnage and cost of the structure, composite steel and concrete chord columns may be utilized. Using concrete in chord columns will most likely provide a lower unit price for strength and axial stiffness.

.,

I 2 Moment Resisting Frames

Thc moment resisting frame consists 01 horizontal and vertical members rigidly connected together in a planar grid form which resists lateral loads primarily through the flexural stiffness of the members. Typical deformations of tha moment resisting frame system under lateral load are indicated in Fig. 4.4. A point of contraflcxure is normally located near the midheight of the columns and midspan of the besms. The lateral deformation of the frame is due partly to the frame racking, which might be called shear sway, and partly to column shortening. The shear-sway camponen1 constitutes approximately 80 to 90% of the overall lateral deformation of the frame. The remaining portion of deformation is due to column shortening (cantilever component or so-called chord drift).

>lomen1 rcs~.ting lramrs h ~ v e advantages in high-ri5e conslruclion due lo their f lex- ibility in nrchitsclural planning. A moment reslbling frarnr. may he placed in o r around tltc core, on the exterior. or throughout the interior o f the building with nlinimll con- 5traint on the olannine module. ~ h ; frame mav be architecturallv exposed to express the ~~~ ~~ u . . gridlike nature of lhs structure. The sp3cing of lhs column: in n moment resisting frame c ~ n match !hat required fur grnvity lraming. In lac1 ths stecl u e ~ g h t prenlium for iatual - ~

frame resistance decreases with increasing gravity londs on the frame

54 Lateral Load Resisting Systems [Chap.

(a)

Fig. 4.3 Typicul corlncrlion debiir. lo) CUF. (b) EUF.

sect. 4.11 Braced Frame and Moment Resisting Frame Systems

. .. (b)

~ i ~ , 4 3 ~ ~ ~ i ~ ~ l ~ ~ ~ n ~ ~ t i o n dttniis. (n) CBF. [b) EBF. (Codinued) ...

rig, 4.4 ~~~~~t rwirting derurmntion under Inter loud. (01 Frame deformntion.

behavior.


volves a transfer of shear forces from the top to the bottom of the building. Figure 4.7 shows the truss and frame deflections if each resisted the full wind shear. The distrihu- tion of wind shear between lruss and frame can also be noted. Frame-truss interacting systems have a wide range of application to buildings of up to 40 stories in heieht.

In general, core trusses are combined with moment frames located on the building perimeter,where the column spacing and the member proportions of the frame may be appropriately manipulated. Optimum efficiency is obtained when gravity-designed columns are used as buss chords without increasing them for wind forces. These are then combined with gravity-designed exterior columns and spandrel beams with rigid

SEMIRIGID BOLTED CONNECTION RIGID FIELD

WELDED CONNECTION

RIGID CONNECTION SHOP WELDEDIFIELD BOLTED WITH COVER PLATES

RIGID CONNECTION SHOP WELDEDIFIELD BOLTED WITH END PLATES

I J sect. 4.7, Braced Frame an. Moment Resisting Frame *terns 59

3~ connections. If the lateral stiffness of the system is adequate, this then would ~ r o d u c e

, an oplimal design. If additional stiffness is required. the decision of whether to Increase

... the core or the frame members depends on the relative efficiency of the two components. The frame beam spans, story heighls, and core uuss depth are key parametcrs. Tension or uplift conditions may limit the possibility of increasing chord columns.

P v:

DEFLECTION

> FRAME S H E M

SHEAR

~ i g . 4.7 ~mmc-truss inlemeting rsrlcm. Fig. 4.6 Mamcnt resisting frame connection types.


PROJECT DESCRIPTIONS

Sanwa Bank Tokyo, Japan

Architect Structural engineer Year of completion Height from street to roof Number of stories

Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Maximum lateral deflection Design fundamental period Design acccleration Design damping Earthquake loading Type of swcturc

Foundation conditions Footing type Typical floor

Story height Beam span Beam depth Beam spacing Material

Slab Columns

Size at ~ o u n d floor Spacing Material

Core

Nikken Sekkei Ltd. Nikken Sekltei Ltd. 1973 99.7 m (327 ft) 25 4 Office Stmcmral sleel 3 Wa (60 p ; ~ Not available Not available 3 sec in both directions

20 mg: 40 mp for seismic loading 2% of critical C = 0.10 Combination of rigid frames and eccentric K bracing Alluvium and diluvial gravel Raft on reinforced concrete driven piles

3.84 m (12 f t 6 in.) 24 m (78 ft 9 in.) 850 mm (33.5 in.) 3.15 m (10 ft 4 in.) Steel, grade 400 MPa (58 ksi) 2d floor and above; concrete-encased steel below 2d floor 120-mm (4.75-in.) reinforced concrete

-100- by 400-mm (16- by 16-in.) H sections 3.15 m (10 ft 4 in.) Steel. grade SM 490.483 MPa (70 ksi) Shear walls below ?d floor, 800 mm (31.5 in.) thick combined rigid and braced steel frames, grade Shl490, above 2d floor

Sect. 4.11 Braced Frame and Moment Resisting Frame Systems 61 , . .I.. ,ir. together u,ill~ the rigid frames. The di3gOIIal members of eccentric K-bmccd framcs do no!

L.? ' intercect at the cenkr of the beam. Thus yielding 1 the center of the beams will occur be- .......-- ~

fore braces buckle, ensuring ductility and allor;ing for adjustment of the f m e ductility (Figs. 4.9 to 4.11). This hor, been confnned, both experimentally and theoretically. ~.

Ductility and strength are ensured by using acomposite beam for the 24-m (78.9-in.) office floor spans. This also minimizes vibration disturbance due to people walking, as was confirmed through a composite beam mock-up test

Precast concrete panels faced with granite are used as cladding material, providing a solid appearance to the building (Fig. 4.12). The panel fixings were designed so that during an earthquake, the panels can follow the building deformations without damage or risk of dislodgement. This was checked using a two-story two-span full-scale model.

111 designing the Saniva Bank bullding for carlitquakc and \bind loads (Fig. 4 8 ) , it was decided to place ccce~llric K-br3c:d frnmea al npproprio~c lucntions such !hat [hey uill act

62 Lateral Load Resisting Systems [Chap. 4 I Sect. 4.11 Braced Frame and Moment Resisting Frame Systems "7 ~k:!

Fig. 4.8 Snnwil Bank. Tokyo, Jnpun.

Lateral Load Resisting Systems [Chap. 4

4 u , m 1 t* %%%%%%%%%%'b b b

Fig. 4.10 Fmme~arL; Snnwn Bank.


i

i Fig. 4.11 Specimen olecc~nlr ic I( Imme; Snnno Bnnk

I


PLAN

I\ vibration

COLUMN PANEL FASTENING

( a )

Fig. 4.12 Dclniir otprerut concrele pnnel; Snnwn Bank.

, , , , r 4,., - I ',/ I.. " .I

,, ...,-.. -2 -..,.-..- E . - - 2 .-.,< T. .. ...!?.L::i; , " ; ; , ,Ci.. ..:* :" *.>' ,'I.. <;I , ,. ,;; : ' ,:i ,.$"

I 6 0 0 0 A SECTION

(4 Fig. 4.12 Dctililr o f prcrort rnncrclc pnnel: Scnwn Bunk. (Conrir#ucdl

67


ACT Tower Hamarnatsu City, Japan

Architect

Structural engineer Year of completion Height from street to roof


Building use

Frame material. Typical floor live load

Basic wind velocity

Maximum lateral deflection

Design fundamental period Design acceleration Dcsign damping

Earthquake loading Type of structure Foundation conditions

Footing type

Typical floor Story height

Beam span

Beam depth

Beam spacing

Nihon Sekkci Inc. and Mitsubishi Estate Co. Ltd.

Nihon Sekkei Inc. 1994

21 1.9 m (695 ft)

47 - Hotel, offices, retail space Steel

5 kPa (100 psfJ

30 mlsec (67 mph) Hl2OO. 100-yr return period wind

4.52.4.73 sec 52 mg peak. 100-yr return period

1% serviceability. 2% ultimate C = 0.06

Braced frames

Clay, sand, and gravel Piles 1.5 to 2.4 m (5 lo 8 ft) in diameter. 25 to 30 m (82 to 98 it) long

4 m (13 ft) office: 3.15 m (10 f t 4 in.) hotel

17.5 m (57 f t 5 in.) max. office: 10 m (33 ft 10 in.) hotel 850 mm (33.5 in.) office: 700 mm (27.5 in.) hotel 3.2. 6.4 m (10 f t 6 in.. ?I ft) office: 3.2, 4.27 m (10 h 6 in.. 14 ft) hotel

Slab 135- to 180-mm (5.25- to 7-in.) concrcte Columns

Sire at ground floor 750 by 600 mm (30 by 24 in.) Spacing 3.2 and 6.4 m (10 ft 6 in. and ?I ft)

Corc X- and K-braced framer

Braced frames were used lo increase the stiffness of the ACT Tower (Fig. 4.13) and to achieve an optimum structural system (Figs. 4.14 to 4.16). Three u.ind-tunnel tesls were performed:

I. A wind pressure test to evaluate facade pressures

2. A wind force test to measure the horizontal force, overturning moment, and tor. sional moment

Sect. 4.11 Braced Frame and Moment Resisting Frame Systems

3. A dynamic test to check the dynamic analysis results I The dynamic annllsis war performed using the mean and the standard dc\'iarion as

well as the power spectruln of the ovrnurning moment and the torsional moment coci- I cienls obiined inthe wind force test 1

i The building response specva are obtained by combining the wind spectra (for the x, y, and 8 directions) and the magnification factors versus frequency curve. As the building cross section is ellipsoidal, special consideration was given to getting the maximum response values used in the design in the x, g, and E directions. The dynamic stability and the possibility of galloping were also checked.

Strong winds can occur several times a year, causing uncomfortable building mq- tion. In order to avoid this problem, a damping systcm has been installed to reduce the - . acceleration in they direction.

The building site is located in a very active seismic area. The largest eanhquakes in this zone to dare were of magnitude 8. A special seismic analysis was performed using the data of the three largest earthquakes that have originated in this area in order to model the earlhquake waves and the maximum possible accelerations for the ACT Towcr site. These 3 earthquake waves were 416 gallsec (550 mmlsec) (Ansei Tohka

1 earthquake); 150 gallsec (320 mmlsec) (Nohbi earthquake): and 332 gallsec (850 mmlscc) (Tohnankai earthquake).

i

Fig. 4.13 ACT Towcr. Humnmolsu City, Jnpnn.


M i c a 1 Structural Plan (Hotel)

>pica1 Structuroi Plnn (OCrice)

Fig. 4.14 'Typical slruelurul plunr; A C T Toner.

72 Lateral Load Resisting Systems

I! Ti%-

Fig.1.16 Y5A frame elemlion; ACT Tower.

Tllr typical floor pi2n of the Kobe Ponopix Holcl (Fig. 4.17) is .an oval, rncnsuring 7j.5 m (24.4 Ir) in the earl-weal dirccrion and 13.5 rn (4.4 f r ) in the north-soutl~ dirucrion IFlp. 4.18). Above the fifrh floor of the high-rise p m . strength and ductility are provided hy

[Chap. 4

I


Nikkeu Sekkei Ltd. with Portopia ~ o t ~ l Design Of ice

Nikken Sekkei Ltd. with Portopia Design Office

Year of completion 1981 Height from street to roof 112 m (367 ft) Number of stories 31

Number of levels below ground 2

Hotel Fnme material Structural steel Typical floor live load 1.8 kPa (36 psf) Basic wind velocity Not available

Maximum lateral deflection 350 mm (13.75 in.) Design fundamental period 3.5 sec transverse; 3.6 sec longitudinal Design acceieration 20 mg; 35 mg for seismic loading

2% Earthquake loading C = 0.08

Type of structure Moment frame and braced frame i Foundation conditions . Fill over alluvial and diluvial strata

Raft on prestressed concrete driven piles

3.02 m (9 ft l l in.) 7.5 and 6.75 m (24 ft 7 in. and 22 ft 2 in.) 800 mm (31.5 in.)

7.5 m (24 ft 7 in.) Steel, grade 400 and 490 MPn (58 and 70 ksi) 5th floor and above; concrete-encased steel below 5th floor 130-mm (5-in.) reinforced concrete

Columns

Size at ground floor I100 by 1100 mm (43 by 43 in.) Spacing 7.5 m (24 fi 7 in.) Material Steel encased in 24-MPa (3400-psi) con-

crete Core 600-mm (24-in.) concrete shear walls be-

low 5th floor, smctural steel rigid frames 5th floor and above


using a reinforced concrete rigid frame. The fifth and lower floors, which have a larger story height. have a composite structure of shear walls and rigid frames made of steel encased in reinforced concrete (Fig. 4.19).

The site is part of about 500 ha (1200 acres) of artificially reclaimed ground. which has been filled over a oeriod of 10 years, starting in 1965. Before building construction commenced, the site Was preloaded. theoretically completing sett lemen~of the former 12-m (40-it)-thick sea-bottom clay layer. Because the building weigh1 is about 100.000

I k Sect. 4.11 Braced Frame and Moment Resisting Frame Systems 75

tonnes (1 10.000 tons), a basement withgood foundation load balance was possible, with the weight of h e excavated soil being designed to exceed the weight of the building.

Piles of about40-m (130-11) length were used. The building is supponed by using the diluvial layer as the bearing stratum. In pile design, pile groups were used wherever possible to cope with unmeasured ncgative friction. Structural safety was confirmed by per- forming a seismic response analysis of the building-pilc-bearing stratum composite form against horizontnl seismic loads.

The floor plan has an unusual form, so various wind tunnel tests were performed to investigate such factors as the wind force coelficicnt. the wind pressure coefficient, nm- bienl wind velocity, and the dynamic stability against wind. In everything from the structure itself to cladding matcrinls, external doors and windoms, and ground-lcvel wind velocity, wind tunnel test rcsulls were used to ensure adequate safety and serviceability.

Fig. 4.18 Typicul slructurul noor plnn; Kobe Purlopin Hotel

Fig. 4.17 Kobc Porlnpiu Holcl. Robe, Japan.


\ /

I 9 VrnrnesorR; Kobe Portoplu Hofcl,

Braced Frame and Moment Resisting Frame Systems 77 -?,.. .*+. 8:;: Nankai South Tower Hotel ah @ Osaka, Japan * ,. ..,, j Architect &( 18, ,: Swctural engineer

I $& 41 :Year of completion

@ Height from street to roof .,g~, ~* .~ . . ~ . Number of stories :*.: I,S ,

Number of levels below ground 'A, : :I: Building use &~ .?,. Frame material 73,' .,: .: .

Typical floor live load

Basic wind velocity

Mnximum lateral deflection


Design damping . . ., .,,. Eanhquake loading :, ,. . . Type of structure


Footing type

Typical floor Story height Beam span

... 2:. <- Beam depth

Beam spacing Material

Slab Columns

Size at ground level Spacing Material

Core

Nikken Sekkei Ltd.

Nikken Sekkei Ltd.

1990 147 m (482 ft)

36 3

Hotel

Structural steel upper floors; concrete-encased structural sleel plus concrete shear walls lower floors

1.8 kPa (36 psO

35 d s e c (78 mph) Not available

3.24 sec transverse; 3.03 scc longitudinal Level 1 EQ. 13 to 25 mg; level 2 EQ. 21 to 40 mg

2% C = 0.120 Level 5 and above, rigid frames; level 4 and below, combined frames and shear walls Grnvel

Cast-in-place 2-m (6.5-fr)-diameter bored piles 10 m (33 ft) deep

3.2 m (10 ft 6 in.) Primnry. 10.5 m (34 h 5 in.); secondary, 5.4 m (17 ft 8 in.) 850 mm (33.5 in.) 2.625 m (8 ft 7 in.)

Steel, grade 400 and 490 MPn (58 and 70 ksi)

140-mm (5.5-in.) concrete on metal deck

1300 by 1300 mm (51 by 51 in.) 10.5 m (34 ft 5 in.) Steel, grade 49 MPa (7000 psi) Shear wall. 34-MPa (3400-psi) concrete. 350 mm (14 in.) thick


This hotel was constructcd over a railway station, which had been designed and constructed by another firm up to the fourth floor 10 years earlier (Fig. 4.20). An expansion of about the same extent was planned even in the original design, but there existed limitations with regard to theallowable stress of the already constructed parts, including the piles. While over the course of I0 years structural codes had been modified, mal;ing it more difficult to expand buildings constructed before the code changes, the design tech-

Sect. 4.11 Braced Frame and Moment Resisting Frame Systems 79 I niques for high-rise buildings had not fundamentally changed, so the strength ofthc already constructed parts was for the most pan adequate. However, there was n planning regulation change in that guest rooms must now have balconies, and it was necessary to comply with the desires of a desiener. which chaneed the plans considerablv.

?hi increased weight due to balconies was handled by changing the spciific gravity of the concrete irom an original 1.8 lo 1.65. In the original design, slanted columns had ranged from the sixth to the twentieth floors, which was due to changes in thc spans of t h e k o ~ e r and lower floors. and the desiener wanted to reduce thisnnee to dctwecn . . - llourr 9 m d I?. Tu Improxc the ~.nruing reduction in h~l id lng rigidlly, the s n c 01 tile c x ~ c n l d columns ~ 3 s incrcarcd. Thir supprcsrcd ihc overall hcnding deformation, and at the same lime the inner coiumns were effectively used as shear columns. External columns are larce boxed members. so in the lencth direction the oerimeter irame is used - - to rcsirt 111 01 ihe horironnl loading (Figs. 4 21 and I.??).

To facilit3te conrtruclion, bnlconics were dcsigncd in ihc L shops uilh 3 length of 10.5 m 134 it 5 in.). Pn:.lr~.swd cuncr2ls. oniv 90 mm 0 . 5 in1 thick. u a i used lo inioi- mize the weight.

A composite floor, fire rated for 2 hours, was used in the typical guest room. The deck has to be of the linked beam type (which covers at least two beam spans). In unit bath areas, which had to be partially dropped, ordinary slabs using a flat deck were employed.

Fig. 4.21 Typlcnl noor plan; Nankui South Toscr Hotel.

Fig. 4.20 N ~ n k o i South T u n ~ r Hutcl, Omku, Jnpon.

Fig. 4.22 Fmmcrork; Nnnkni South Tower Holrl.

80

:g+ .$ +J: .$I Ssct 4.11 Braced Frame and Moment Resisting Frame Systems 81 i7.5. 1 ~..= 9 World Trade Center w *. : *.. I Osaka, Japan

ji *", Architect

' S . ~ j < *. . -.: i Structural engineer ..:.

Year of completion Height from street to roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Maximum lateral deflection

Design Fundamental period Design velocity

Design damping Eanhquake loading

Type of shucture

Foundntion conditions

Footing type

Typical floor Story height Beam span Beam depth Beam spacing Matenal

Slab Columns

Size at pound floor Spacing Material

Core Material

Ni ienSekke i Ltd. with Mancini Duffy Associates Nikken Sekkei Ltd. with Mancini Duffy Associates 1994 252 m (827 ft) 55 3 Office

I Structural steel 3 kPa (60 psf) 40 d s e c (90 mph) 1300 mm (51 in.). 200-yr return period wind 5.3 sec transverse; 5.8 sec longitudinal Level 1 EQ. 250 mm/sec (10 inJsec); level 2 EQ. 500 mmtsec (20 in./sec) 2% C = 0.05 longitudinal; C = 0.075 transverse Rigid frames with core braced trans- versely 20-m (65-ft 7-in.) fill over alluvial clay and sand strata Cast-in-place steel-lined bored piles belled at their bust

4.0 m (13 ft 1.5 in.) 16 rn (52 ft 6 in.) 900 mm (35 ft 5 in.) 3.2 and 9.6 m (10 R 6 in. and 31 ft 6 in.) Steel, grade 400 and 490 MPa (58 and 70 h i ) 175-mm (7-in.) concrete on metal deck

650 by 850 mm (25.5 by 33.5 in.) 3.2 and 9.6 m (10 ft 6 in. and 31 ft 6 in.) Steel, grade SM 53B Steel fmmes, braced in transverse direction Stee!, grade 490 MPa (70 ksi)

82 Lateral Load Resisting Systems [Chap. 4 Sect. 4.11 Braced Frame and Moment Resisting Frame Systems

This 252-m (827-it)-high building stands on reclaimed land in the Osaka Nanko (soulh port) area (Fig. 4.231. As a consequence, the design of the foundation structure and the resistance to wind were painstakingly invesligated.

A lypical high-rise floor is 36 by 70 m (1 18 by 230 it), and the building has an extremely slender form where the ratio of shorl side lo heieht is 1:7 (Fies. 4.24 and 4.25). - . Beiuw lhc sevenlh flonr, colu~nns ard trnesiendd lo tltc perimeter, iormiltg a supenruss fr3nlc in order lu slrenglllen lile rusistnnce to !r'~nd and uanhquakcr. and !$idcly distribute nxiill forces of the high-rise building o \cr tht ground. Titis forms n ' h ~ r r " for [he tower, which i s integrated with the undeirground slructure.

Wind is a more dominant laleral load for this building than earthquakes. The wind load for the design, including vibration assessment, was determined from the rcsull.; of wind tunnel testing. The testing investigated instabilities as well as accelerations likely to affect the comfort of occupants, unstable vibration due to wind, and habitability during swaying of the building duc lo wind forces.

As the site is anilicially reclaimed land, and settlement due to canh filling is not complete. the cast-in-place steel-pipe concrele piles used are coated with asphall to reduce friction with the surrounding ground. The bearing stratum is a diluvial sand) gravel layer around 60 rn (197 it) below ground level.

Fig. 4.24 Typical noor plnn; World Trndc Ccnlcr, Oruku.

Fig. 4.13 World Trode Ccnlcr, Omkn, h p u n .

I . . . . I . . - I . . ! . - ! . . - ! 0 0 9 B m 0

Fig. 4.25 Frun~c,vorli: World Trndc Ccnlcr, Osuha.


Kobe Commerce, Industry and Trade Center Kobe, Japan

Architect Nikken Sekkei Ltd. S~uctural engineer Nikken S e k e i Ltd.

Year of completion 1969

Height from svect to roof 110.06 m (363 it)

Number of stories 26


Building use Office

Frame material Steel

Typical floor live load 3 P a (60 psfJ

Basic wind vclocity Unknown

Maximum lateral deflection HI400 Design fundamental period 3.42 scc each direction

Design accclcration 20 mg elastic: 40 mg elastoplastic

Design damping 2 %

Earthquake loading C = 0.085 Type of structure Perimeter framed tube \\,it11 diagonally

braced core

Foundation conditions Alternating gravel and diluvial clay strata

Footing type Raft

Typical noor

Story height 3.84 m (12 ft 7 in.)

Beam span 9.45 m (31 ft)

Beam depth 600 mm (24 in.) Beam spacing 3 m (9 ft 10 in.) .

Material Steel. grade 400 MPa (58 ksi) above 1st floor, concrete-encased structural steel 1 st floor and below

Slab 160-mm (6.25-in.) concrctc on metal deck Columns

Sire at ground floor 700 by 700 mm (27.5 by 27.5 in.)

Spacing ' 3 m (9 ft 10 in.) Material Steel, grade 490 MPn (70 ksi)

Core Strucmral steel with prestressing-bar diagonal bracing

This building is structurally characterized by its "tube-in-lube structure." which consists of perimeter wall frames with 3-m (10-it) spans and internal braced frames using prestressing steel bars for diagonal bracing (Figs. 4.26 to 4.28). For the purpose of efficiently increasing the earthquake resisting capacity of a building, it is preferable to design its slructure in a bending failure mode so as to disperse the yielding of frames


during an earthqualie. To achieve this objective, the tube-in-tube structure was adopted $! for this building. 1 !

Fig. 4.26 Kobc Cemnlcrre, Industry nnd Trndc center, J , , ~~ , , .

For the braced frames using prestressing steel bars, F13T steel bars serve as diagonal braces (Fig. 4.29). These braces have a wide elastic range and thus can resist the maximum seismic forces within the elastic region. This enables the overall struchlre to act in a bending failure mode, thereby securing stable recovery characteristics. In this way the structure is designed to be effective from an aseismic viewpoint.


3 Ir

g: :!<: si ,.,, :? *x: isj. ?..

P e r i m e t e r f r a m e B r a c e d f r a m e Fig. 4.27 Fmmcnorli: Kobe Commerce, lnduslry and Trndc Cenlcr.


P e r i m e t e r B r a c e d Ln

4 . f r a m e \ / f r a m e

1 3 6 . 9 0 0 ]

Fig. 4.18 Typiutl rtructurnl noor plan: Kobe Commerce, industry nnd Trndc Center.

Sect 4.11 Braced Frame and Moment Resisting Frame Systems 89

Fig. 4.29 Specimen of brnced frnme wing prcstruing bars; Kobe Commerce, Industry and Trade Center.

90 Lateral Load Resisting Systems [Chap. 4 Sec t 4.11 Braced Frame and Moment Resist~ng Frame Systems 91 I E I Marriott Marquis Hotel New York, N.Y.. USA

Architect John Portman Associates

S t ~ c t u n l engineer Weidlinger Associates Year of completion 1985 Height from street to roof 175 m (574 ft) Number of stories 50 Number of levels below ground 2 Building use Hotel Frame material Steel Typical floor live load 2 kPa (40 psO Basic wind velocity 36 mlsec (80 mph) Maximum lateral deflection 300 mm (12 in.), 100-yr return Design fundamental period 5 sec

Design acceleration 20 mg peak. 10-yr return Design damping I% serviceability; 2% ultimate Earthquake loading Not applicable Type of SlNcture Braced and rigid frsmes Foundation conditions Rock, 4-lvlPa (40-tonlft') capecity Footing type Spread footings Typical floor

Story height 3.05 m ( I 0 h) Beam span 8.53 m (28 ft) Beam depth 460 mm (I8 in.) Beam spacing 3.05 m ( I 0 ft) Material Steel, grade 250 MPa (36 ksi) Slab Precast concrete. 300 mm (12 in.) thick

Columns 610- by 610-mm (24- by 24-in.) built-up I shape from 90- to 203-mm (3.5- to 8-in.) plates, grade 30- to 35-MPa (4200 to 5000 psi) steel

Core Reinforced concrete beam and column frame with 13 columns in a circle

Facing Times Square on a block front between 45th and 46th Streets. the new 167.000- m' (1.8 million ft') hotel rises 50 stories above the street (Fig. 4.30). The two sheer fin walls along the two side streets contrast sharply with the stepped and skylit facade facing Broadway. It is surmounted by a projecting, rotating cocktail lounge seven storics above the ground, actually the lobby level of the hotel. Above are five-story packages of hotel rooms that are stepped back and forth between the tin rraalls like a giant's ladder. The first six floors of the building contain public facilities, including a 1500-seat theater, a ballroom, exhibition and meeting rooms, and revail space.

Fig. 4.30 hlnrriott hlnrqnir Hetcl, New York, undcr construction. (Pl!aro b), Jennreier Leby.)

92 Lateral Load Resisting Systems [Chap. 4 .

A circular concrete core, wilh 12 Tivoli lighted elevators and four enclosed elevators, rises from the street level through the public levels, breaking free at the lobby level, into a spectacular 35-story atrium (Fig. 4.31). I1 terminates at a multilevel rotating rooftop restaurant Skylights on the east facade, between the five-story packages of hotel rooms, bring daylight into the atrium, shining down onto the hotel lobby. The 3 5 guest room floors,. wilh 1876 rooms, are disposed in rectangular bands around the atrium. From the guest floor corridors, with their projecting planters presenting an im- age of the hanging gardens of Babylon, one can look down at the parklike lobby surrounded by colorful restaurants.

As a structure, the building is equally unique, consisting of a steel-framed structure surrounding the slip-formed concrete core. Between the two I I-m (36-it)-deep fins, a 34-m (1 12-it) clear span is framed using girders below the lobby and five-story Vieren-

Pig.4.31 Elcvntar core rises 180 m (600 10 through ntriurn to r~volving rc;tnuronls: hlnrrintt hlurquis Hotel.


deel frames for the packages of hotel rooms. These hotel room oackares were oririnallv . - . conceivrd to,be supponed by slerl trusses. The Vierendeel irames nor only climinatcd rhc trusses, but being tied into the s~de-wing venical fr3mcr. pro\.ide st i ifnes in the north-south direction. Stmctumlly. the building is a U with coiumns 8.5 m (28 it) on center along the thrcu sides, with the closure pro\*idcd by the 31-01 ( 1 12-fi)-\pan V~rren-

.deel frames. The two sides of the buildingmd the back are rigid iramcs above the lobby and arc vuased hctween lobbv and round floor. To urovidc the reuuircd 131~ra1 stiffness in the iront, the vierendeel;, combined with a &divided vertical frame on the two sides, form superframes. In order to avoid the added columns at the ground level, the columns placed 6 m (20 fl) from the nonh or south side are. in fact. nosts with vertical . slip joint5 at midhe~gltt betuecn floors.

At the hack of the building, along column line I?, a single irantc. cross hrsced bclow the lobhv. oro\,ides the stiffness in the north-south dirxrion. Sincc the eroun of

- ~ - ~ r -~

three superfr&nLs in the front (at column lines 3.4, and 5 ) have substantially different stiffness, a process of fine-tuning wns undertaken to match deflections betwccn the packet of superframes and the single frame as closely as possible. The purpose of this exercise was to avoid torsion in the building. In this connection it should be noted that even if the two were perfectly matched, a 5% eccentricity is required by the Uniform Building Code (UBC) between the centroids of mass and rigidity. This has the effect of requiring a 10% increase in shear carried by the diaphragm above that, resulting from lateral wind iorces.

Below the lobbv. the floor construction is conventional metal deck and concrete fill. . . ~ ~ ~ ~~~~

For the guest room floors, this construction was originally specified. However, since a ceiling is required and since spans for the metal deck are limited, necessitating more beams, an alternative, using long-span precaslconcrete plank without topping, wus chosen, based on economic considerations. Not only did this result in a reduction in the number of steel beams, but it also eliminated a hung ceiling since the underside of the plank is a finished surface. The more than 93.000 mz ( I million it2) of plank used makes this a most dramatic application of plank floors in a high-rise building. As a result ofthe innovative use of both the Vierendeel msses and the concrete floor plank (which are only mar~inallv heavier than the orieinal metal deck and concrete solution). the steel . - . - .. ~

structure with less thon 117 kglm' (?4 psO is extremely efficient and economical. The planks. a p m from providing normal \enicaI load-carrying capacity. arc re-

quired tu provide the d ~ a p h r a ~ r n rrsisuncc, transicrring all lateral force5 to the vcnical \rind irorncs. Becnuse of the height of the building and the unujual configomtiun, this implied special rcquircmel~ts for the plank Bas~cally. the plank l~tusl do rhe fi~llowrng:

I . Support dead and live loads 2. Transfer wind iorces to bracing members

3. Transfer column-stability forces to bracing mcmbcrs 4. Transfer forces between bmcing members

Since the planks are an inherent part of the stability of the structure, p l ank were placed, grouted, and welded in sequence with the erection of the stccl irame. A rapid- setting, nonshrink grout with high early strength was specified for the grouting o f the joints between ulanks. These ioinls. which have shear kevs with castellations. have been . ~ -~~

ihuirn hg cp&itncnt tu proCldu adequate shenr strcng;h for diaphragm action with n grnut strength of 17 >!Pa (2500 psi). Fur this project. a design strength of 35 hlPn (5000 psi1 w:!s spec~liud to prnvidc higher carly strcngth and 2 magin ofs;tf<ty lor the ultremc ueather condition5 to bc encountered during the construction cycle. Sinc? nu topping is uacd, dixphragm action rdllrs solely un the ~nrcgrit) of th~. j o~n t 2nd thc anchor.


Taj Mahal Hotel Atlantic City, New Jersey, USA

Architect

Structural engineer

Year of completion

Height from street to roof Number of stories Number of levels below ground Building use Frame material


Basic wind velocity

Design wind load deflection

Design fundamental period Design acceleration Design damping

Eanhquake loading

Type of structure


Footing type

Typical floor

Story height Truss span Truss depth

Truss spacing Material Slab

Columns

Size at ground floor Spacing

Material Core

Francis Xavier Dumont

Paulus Sokolowski and Sanor, Inc. 1990

128 m (420 ft) 42 0 Hotcl

Steel with precast concreie perimeter beams

Rooms 2 P a (40 psO; corridors 4 W a (80 P ~ O 40 d s e c (90 mph) 254 mm (10 in.) 3.0 sec

1.8 mg rms, l-yr return period 1% scrviceabiiity

C = 0.037; K = I .O (did not govern design) Staggered steel trusses and braced steel core transverse, rigid perimeter frame longitudinal direction 27 m (90 ft) of loose sand and thin organic strata over dense sand

355-mm (14-in.)-diameter steel-shell driven cast-in-place concrete piles. 1500-ki-4 (165- ton) capacity

2.69 m (8 ft 10 in.) 20.7 m (68 ft)

2.69 m (6 ft 10 in.) . 9.14 m (30 ft) Structural steel

100-mm (4-in.) precast slabs with 100- mm (4-in.) cast-in-place topping: 3 5 . ~ ~ ~ (5000 psi) concrete

Built-up steel. 2230 kglm (1500 Iblft)

9.1 by 20.7 m (30 by 68 ft) Structural steel, grade 350 MPa (50 ksi)

Braced steel frames, g n d e 350 MPa (50 h i )

r S e c t 4.11 Braced Frame and Moment Resisting Frame Systems 95

When the developer wanted a 1200-room high-rise luxury hotel right on the exposed oceanfront, a prime concern of the designers was occupant comfort. Building sway and acceleration had to be minimized.

Preliminary analyses and cost studies were made of four basic structural systems:

Steel staggered truss with concrete floors

Concrete frames with shear core and other shcar walls Concrete-fnmcd lube with concrete shear core Steel-framed tube with shear core

All svstems excenl the staeeered truss reouired relativelv laree shear wallr to con- -- . . ~ ~

trol ssra).. and the hc iv~ly l o ~ d e d wills rcquircd l;lrgc and cxpcnsivc fueling s)ste,ns. In iddillon lhe slccl-ir:mi.d lube h:!d p r u b l ~ m ~ of uplift. Rcl;,tive car15 w r e .

Steel staggered truss 1.00

Concrete frames and shear rvnlls 1.25

Concrete-framed tube 1.10 Steel-framed tube 1.40

The stagg~.rr.d truss f r~ming syrlcm rvas dcvr.1npr.d Ry a U S . Steel-spunsured rc- s23rch learn nor l ing 21 hl.1.T. i f , the inid-1960s. Its hilsic ~ I C ~ I C I I I is thc \ I U T ) - ~ U L . ~ I ~ U I I

which spans the full width of the buildine at alternate floors on each coiumnlinc. ilcncc the floor spans from the top chord of one truss to thc bottom chord of adjacent trusses so that each truss is iondcd on both the lop and the bottom chords and is laterally fully restrained.

Because all eravitv load is suooorted at the oerimeter of the buildine. the tvholc of & . . . th? huild~ng a d i ~ l ~ t c3n hi. ~ I I O ~ I ~ I L L . ~ 10 rdsist ovcrturnlng eff~.cls .

Lxcral iorc~.s are transmitted from floor to flour d0u.n the building via the llonr dl- aohraems and INSS web members. The oerimeter columns c a m onlv-axial load in the . - . . transverse direction and can therefore have their strong axis oriented longitudinally to form part of a longitudinal rigid frame.

The layout of the Taj Mahal Hotel (Fig. 4.32) with a central double-loaded corriddr suited the staggered truss arrangement as it allowed the provision of a Viercndeel panel midspan, where the shear is least, for the corridor.

With the structural svstem selected. a wind tunnel studv rvas canied out to determine atruculnl forces, d)n:trnic bch:,\,ior, c1;ldding pressures, 2nd cnr,irnnnicst31 eifccts s1 ground level. Frdm this. the design l;ltcr:,l looding, building driit, 2nd acceleration ncrr. established.

Because this is a tall buildine for a staeeered truss svstem. the shears in the floors uu

were an important design consideration. The 200-mm (8-in.)-thick slnbs comprise precast pretensioned concrete p lank tapered on their top surface from 127 mm (5 in.) thick midspan to 76 mm (3 in.) thick each end, where they are supponed on top of the 254-mm (IO-in.) -!vide flange steel truss chord, and a cast-in-place topping. The shear connection between floors and trusses is achieved by stud shear connectors (Figs. 4.33 and 4.34).

Because of functional and architeclural requirements, the staggered truss systcm could not be used at all locations. As a consequence, two other systems were used, a core frame and an end frame. The core framc consists of a truss system with n truss at every floor. but with n vertical stiffness to match the staggered trusses. The truss at every level !\,as required to carry shears from lateral loading without reliance on the floor diaphragm which, at this location, is heavily penetrated by service openings.


The three-bay end frame comprises a diagonally braced center bay and outer bays of rigid framing connected to large perimeter columns. This frame is 13.7 m (45 ft) wide compared to the 20.7-m (68-ft) width of the typical frames (Fig. 4.35).

Wind shears are transferred to the foundations by embedding the bottom chords of the lowest trusses in large concrete-gnde beams. On the lines where the lowest truss

Elg. 4 3 2 Toj hfnhnl Hotel,AtlnnUe City, New Jcmey.


:gi ..i' .@:, was one story above the footings, a diagonal brace was provided at the columns to trans-

(g: fer the load to a steel beam embedded in the footing, similar to the adjacent truss hot- ._. tom chord. A pile cap at a typical staggered truss bay is 7.6 m (25 ft) square and 2.9 4 . , (8 fi) deep, supported on 36 piles. . , , ,

, ..:.- Both structural steel and concretespandrel beams wereconsidered. with the lnnerh.ino 1 selectcd as they best sui ld architectud and fire-nting rquiremenk. lllc I mrn (48- by 12-in.) beam rigidly connwtedtothc largrrxtcriorcolumns nnd the small I .*;. .... height created a fnme easily capable of resistine. the lon~itudinal wind forces r~;:. . --. fab&alor cut the 44- and 57~mm~diameter(+l4 &d 818) reinforcing b m and uclded them I ; lo sael Trectians h o l d for bolting nt each end before delivering thcm lo the Prucalcr ~ h . ~~. .... ,,,~

, . finished beams included a shear key and reinforcement for connection to thislabs. .,:,. .;$; ! .,.. ~ -.,,. , . -21 ... ,.- <.,%I ->., ,..**

Fig. 433 Typical noor plnn; Tnj Mnhnl Hotcl.

Typical building exterior column

0 I"+ A490X bolls

1 " Section

Fig. 4 3 1 Spandrel beam delnil; Tuj Mnhnl Hulel.


INTERIOR STAGGERED- TRUSS BENT

\Piles (typical)

CORE FRAME END FRAME

Fig. 4.35 Fromewurk and typical buy reelion; Taj hlnhul Hotel.

It Sect. 4.11 Braced Frame and Moment Resisting Frame Systems

Tokyo Marine Building Osaka, Japan

Architect

Structural engineer Year of completion

Height from street to roof Number of stories Number of levels below ground Building use Frame material Typical floor live load

Basic wind velocity

Maximum lateral deflection Design fundamental period Design acceleration

Design damping

Earthquake loading Type of structure Foundation conditions Footing type

Typical floor

Story height

Beam span

Beam depth


Slab

Columns


Matenal

Kajima Design

Kajima Design 1990

118 m (387 ft) 27 3 Office, retail space, parking Steel

0.79 kPa (16.4 psf) 35 d s e c (78 mph) a1 10-m height

Seismic conlrol 3.31 sec longitudinal; 3.95 sec transverse

4 mg peak, 5-yr return 2%

Base shear coefficient 0.08 hloment resisting frnmc Fine sand Cast-in-olace concrete oile: 22-m (72-ft) length, 5.4-m (7.9-ft) djameter, wiih 4-4 (13-ft) bell

3.9 m (12 ft 9 in.)

21 m (69 ft)

900 mm (36 in:) 6.75 m (22 ft)

Steel, grade SM 490, 483-MPa (70 ksi) tensile strength and below 155-mm (6.1-in.) lightweight concrete slab on cormgated deck

500 by 500 mm (20 by 20 in.)

10.8, 21 m (35, 69 ft) Steel. grade SM 490

Tlic Tokyo hlcrine building i s n 27-story officl: building locatcd in the Osaka burinsrr park district bring develuprd just cast of Osaka Castlc. Japan (Fig. 4.36). The burld~ng urovide~ about 69.000 m' (743.000 11'1 of arca for offices. ret~il . and n~rkina. Cun- . . , - struciion was completed in 1990. i\rchitccturaily the buildins a.as conceived to fir into tht c~~viroo~nentof thc Osaka business p3rk and ro runect the imagl: ofthc cl~ent. Tokyo Marine. As the base of operations in western Japan for Tokyo ~ & n e , the building tvis


Fig. 4.36 Tuk).u Rlurlnc building. Oaaku, Japun.

I Sect. 4.11 Braced Frame and Moment Resisting Frame Systems

designed to have high-tech capabilities, to reflect ils prestige appropriately by its external appearance. and also to be attractive to tenants as office space.

The building has a rectangular plan to fit into the site surrounded by two high-rise buildings on the longer sides. The exterior facade, exposing columns and beams outside the building, brings to mind the simple lines of traditional Japanese wood-frame details and gives a clear identity as well (Fig. 4.37). The lateral force resisting system of the

Fig. 4.37 Pilotis columns: Tokyo hlurtnc building.


building consists of the framed columns interconnected with long-span beams [10.8,21- m ( 7 0 4 ) spans]. This allows for an open public urea at the plaza level of the building and column-free space across the width of the building with a 2.7-m (9-ft) ceiling height on the office floors.

The building is framed in slrucluml steel (Fig. 4.38). Each frame column consists of four vertical membcn joined by short 12.7-m (9-ft)-span] beams to create a three-di- rnen~ional swcture. The combination of the short beams in between the framed column ~~ - ~- ~~~

cicnlcntr and the long-span bcamr cre:ttes unusual static charoclerisrics: migrntiun of column loads. the shorn-span beams being loaded more lightly in bending than the long- swan beams. and an unusunl failure-hinge mechanism for extreme xismic events. m 3 mpiium-rise buildine. short-sean beams yield at their SuppoN under relatively ~~~~ -~ -. . .

low loading levels due 10 a conccntmtion of bending stiffness. Houevcr, in this case the effect of axial deformation; of the frame columns was the dominant mode of behavior. An incremcntallv increasine static analysis on an elastic-plastic model C'pushover" analysis) was c a k e d out to obr3in the sceleton cun,cs for story shear. From this analysis thc formntion of plastic hinges at the supportsof the long-span beams. with the shorn- span burns remaining claslic even at high eanhquake le!,cls, was notablc.

' FRAMED COLUMN


The structure was planned with an unusually long main span of 21 m (70 ft) across the full building width. In such cases the vertical component of an earthquake can have a significant effect on the beam slresses. This was investigated by modeling a typical bay as a two-dimensional frame. Dynamic analysis was carried out using the time history of four earthquake records, inputting their lateral and vertical components simulta- neously. As a preliminary step, the modes of vibration of the structure were obtained, from which it was found that the fifth mode was the first mode in the vertical direction nnd involved axial tension nnd compression in the columns, with all the beams vihrat- ing together. Only at higher modes did the beam vibration become more complex.

The analysis was carried out at two levels of earthquake input. The following were the results.

I. At 250-mdsec (10-in./sec) peak input level. the long-span beams developed large bending moments, in particular high up in the building. It was verified that even including these stresses. the beams remained within the short-term allotv- able stresses according to the Japanese design criteria.

2. At 400-mdsec (80-in./sec) peakinput level, due to the effect of the vertical component of the earthquake. elastic hinees a t the ends of lone-snan beams develooed - u . , ~ ~ - early on, but the structun remained elaslic in its overall heh3vior and did not de- grade its ovsr-ll dynamic stiffness charactarislics. Thc reason for this 1s that scr- tically the period of vibration is much shorter than horizontallv. such that thc stmciurc isnblc to recover its clastic characteristics. From this risult it was concluded that using horizontal earthquake time history records only for the main re-

I sponse analysis was appropriate

I Although the bullding is not of irregular shape, wind tunnel testtng was carned out to investteate the effect of the cxeosed column frames on the surface rourhness dnd ef- - - ~ ~

I fcctive l ront~l ; m a o i the building 11 was also dcsir3ble to prcdiot the vibration b thar - iur of llte build~tig under wind loading, since its period is rei;!tlvclg long. Using ihc prcs- surd cnefficienls from the uind lunncl test. the base shear from u.ind is ahout giro that of seismic ct,ents. In terms of acctl.aation. it uns pr~.dicted (ha1 although the upper lev- zls u,ould e~pcricncc a peak ncceicration of around 4 mK. his ,\auld nut cause any discomfort.

It was considered that since the exposed frame was outside the main building glar- tng Itne, it would not be subject to the same intensity of fire as a normal frame, and therefore could be fire-vrotected to an anoroor~atelv lesser deeree. An annlvsis was oer- iannedonthcframe\<,~rn rubjectedio n.&rtCsdisc/lsrging fro; insidu 1hc ioilding.!~hc rcsults shou,vd that the beams uould hc heated 10 273'C and the columns to ?81'C the outside of their aluminum claddine. Since the critical lemverature for steel in a firs - nlay bc lakc,! ar 350°C ;,\,crape (with 3 n~nximuln uf 45O'C). the conulusiolt unr dnwn tIt:!t no fire protection was needed at ail for the cxlcrn.ll froinc. llpon craminxinn b) the Building Csnlcr Flre Safety and Protection Commitlcc. 10 rnm (0.4 in ) o f fire-res~sl;tnt cladding material was finoily agreed upon, which represented a substantial reduction in fireproofing material.

Fig. 4.38 Framing pcrspcclivc; T n k ~ o hlurinc building.


Kamogawa Grand Tower Kamogawa, Japan

Architect Smcntn l engineer

Y e x of completion Height fmm slreet to roof Number of stories

Number of levels below ground

Building use Frnme material Typical floor live load

Basic wind velocity

Design fundamental period Design damping

Earthquake loading Type of smcture


Footing type

Typical floor Story height Beam span Beam depth

Material Slab

Columns

Size at ground floor Material

Kajima Design

Kajima Design

1992 105 m (344 A)

33

1

Hotel and condominium

Concrete

1.77 !@a (36.9 psO

35 mlsec (78 mph) at 10-m (3341) height

1.92 sec transverse; 1.55 sec longitudinal 2% Shear coeficient0.085 Moment resisting frame with honeycomb damper wall Fine smdy layer over clay layer over shale rock layer

Cast-in-place concrete pile; 19-m (62-ft) length. 1.7-m (5.6-A) diameter, with 2.8- m (9.2ft) bell

2.85 m (9 ft 4 in.) 4.5 m d 9 m (15 and 30 ft) 700 mm (27.5 in.)

Reinforced concrete, normal weight 160-mm (6.3-in.) concrete

900 by 900 mm (35.5 by 35.5 in.) Concrete. 23 to 41 MPa (3400 to 6000 psi)

The Kamogawa Grand Tower is composed of ductile moment resisting frames (Fig. 4.39). The high-rise reinforced concrete (HiRC) conslruction method developed by Kajima Corporation was used. It consists of pure reinforced concrete columns, girders, and floor slabs tvhich are cast on site (Fig. 4.40). The typical floor plan is a stair- shaved vlan alone the catcrior zones. which consists of rceular souare units 4.5 rn (1 5 ~- - ~ ~

11) i n a kide (~i~.-4.41). The standard p a n is chis? 5 m (l<fl) c r c ~ p t ;11 [he central cnr- ridor, sherc !he spitn is 9.0 rn (30 it) hy skipping columns susraincd by rhc cross gird- en. Ths cnure struclurl: is desisncd In be au~roairnalelv ssmmctric ilonl! 45 nnd 135O . - orientations from the orthogon~l so that carthqu&e resistance is balance: in all lateral directions.

106 Lateral Load Resisting Systems [Chap. 4 :@f I j& Sect. 4.11 Braced Frame and Moment Resisting Frame Systems iga. 107

On typical floors, steel plates with honeycomh-shaped openings are installed in the central corridor connecting to the cross girders (Fig. 4.42). Post columns extending from the midspan of upper- and lower-story girders are spliced at midstory using these damper plates, connected by high-strength bolts through gusset plates. Thus the story shear drift is concentrated in the damper plates. Sixteen units of damper plates and post

WALL WITH hONEY- COMPRESSIVE DESIGN COMB DAMPER STRENGTH OF COhCRETE

columns are installed in each typical story. The seismic response of the building is re. duced by the hysteresis damping effect due to the yielding of the steel plates.

The seismic design criteria for two levels of design earthquake were established as follows:

1. Severe earrhquake: The stresses in all slructural members must be less than the allowable values and the story drift must be less than 11200.

2. Worsr earrhquake: Even if the structural members exceed allowable limits, excessive large plastic deformation should not he caused and the story drift must be less than 11100.

Referring Lo the preliminary earthquake response resulls in considcrntion of the hvs- lrresis steel dlmper, the slory shear coufficienls 3rc dcltrm~ncd The design a ind sbc;!rs arc nbnul56Sn of the seismic valucs. In order to secure tbc 111tirn;llu strung11 olthu structural lrame, it U 3 S cst;~bli~hed that th~. m r y shunr cap;,city rrould hc 1.5 times !hat of . . the design earthquake shear forces. The uldmate hcnding and shear strength of the columns was designed to he at least 1.25 times greater than that of the girder, so that yielding to bending in the girders precedes yield in the columns: hut at the tops of the columns, in the lop story and at the bottom of lhc first story, thc bending yield in the columns is considered.

From the earthquake responses of the structure to both severe and worst-case events it was assured that the final desien of the moment resistine frame structure was com- - plclsly s3t1sf~ctog. rvilh respuct tu the design criteria. hlnrco\cr, "ring the huncycor~lb sICL.I plates 35 hysleresi dampcrr. not only a well-bilanced structurs hut also s2vints i n the volume of reinforced concrete may hc realized.

I

Fig. 4.40 Framing rlcvulilln In tllc). dlrcctinn: Knrnugurn Grund Tu$vrr. Fig. 4.41 Tgplcnl nuar plun; Knrnogonn Grnnd Tosrcr.

j

Sect. 4.21 Shear Wall Systems

I ; 1 0 0 1 . I " I ' I ' I 1 0 0

600

SHAPE OF HONEYCOMB DAMPER PLATE

0 0 BEAM w

HONEYCOMB

N

L 6 0 0 - l

MAIN REBAR 10-032 HOOP D13-a100

Fig. 1.42 Shilpe and tnrtntlolion olhoneycornb dornpcr ptolc; Knrnogn~m Grnnd Toscr.

4.2 SHEAR WALL SYSTEMS

I & Shear walls have been the most common structural systems used in the past for smbi i i r $% '

ina building structures aeainst horizontal forces caused bv wind or earthsuakes. With the . - - - i!. advcnt oircinforced concrete, shear wall systems have become widely uscd to stabilize ef-

ficiently even the tallest building slructures. In the last 10 yc-rs, concrete tcchnology has .,: I "; nd\,anccd lo a point where concrete streneths of over 130 hlPa (19.000 psi) arc achievable

in the field. T k s has led to the design o f the proposed 610-m (2000:itj Miglin-Beitler Tower in Chicago (which would become the world's tallest building), relying heavily on a shear wall svslem of verv-hieh-slreneth concrete to resist horizontal forces.

A common shear w d l ; y s t~m used-for tall office buildings groups shear walls around service cores, elevator shafts, and stairwclls to form a stiff box-type structure, such as for the Melbourne Cenlrnl building in Auslralia (Chapter 3.2). In this example the need to enclose and lire-protect 21 passengerelevators, service elevators. two stainvells. lobbies, and service risers created the framework for a niff concrete box-type shear wall system.

In contrast with oftice buildings, high-rise residential buildings have less demand for elevators, lobbies, and services, and hence do not usually have large stiff concrete shear wall boxes to resist horizontal forces. A more common system will incorporate a small box structure around a smaller number of elevators and stairwells, and include discrete shear walls between apartments.

In both shear wnll systems noted, the walls are designed lo canulever from the foundation level. To deslen shear walls -need around service cores. the bcndine. shcar, and - - - !<,arping stroses duc to !\ ind or cmhqoake lo3ds arc combined eith slr:sses due to pmvll) loldc. Indi\,idunl wdl, within thc box system can then hc designed as unit-length u,alls span- nine either noor to flour or bctu,ccn return walls. Reinforcrmcnt is proponioncd as iollon,:

. . 1. Minimum shrinkage restraint reinforcement where the wall stresses are low, which can be for a subsmntinl ponion of the shear wall.

. . .. 2. Tensile reinforcement for areas where tension stresses occur in walls when wind ~ ~ l i f 1 slresses exceed eravitv stresses. - .

3. Compressive reiniorccmcnt with conlinumunt ties u hcre high cumpressi\,e forces rcquir: that ualls b~. des~pned as c o l ~ m n s . Individual shcnr walls, say at the edge of a tall huildinp. are dcsiknrd either 3s blade walls or as coluo~ns rer~sling shcar , . ~ . . - .,. and bending as required. - i ;b

> ,'

. i. Mult i~ le shear walls throuehout a tall buildine mnv be couoled to vrovide additional - - . iramu action and hcncc increasr ovcr2ll building stilfncsr. Coupling can bc realized hy rulalivel) shallow hrader or link b u m s within the ceiling cavil) at each Irvcl or by

I .. means of one- or two-story-high shear coupling walls. By adding a coupling shear wall at a single level, reverse curvature is induced in the core above the coupling shear wall,

I significnntly reducing lateral drift by increasing thc overall building stiffness. As the increase in mass is minimal, there will be an increase in the building's natural frequency.

1 This can be a desirable effect. in oarticular with resoect to achievine an accentablc . . uind-induced ncr~lcmtion response tu cnsurc occupxn~ comforr. Ccntrnl cure hnxus can 31ro hc coupled \In slifi beams nr lri.,sus, ol discrule lc\uls, Id urlcm>l shear u;ills or columns to achieve a similar and more pronounced effect than that noted. Thus the concrete shear wall becomes the central component in a core and oulrigger system.

Many tall buildings undergo torsional loading due to nonalignment ofthe building shear cenar wilh the location of the horizontal load application. Such a situation occurs in the CitySpire Building (Chapter 4.3) due to the asymmetry of Ule location of the shear wall boxes. Torsional loading can also be induced in a building such as Bourke Place (Chapter


3.2) due to theneriodic sheddine of windvoltices altemalelv fmmeachside of h e shucntre, - moving the insvmtmcous center of pressure oul nf line aid) thc building's shearcenat.

Boxed shear all systems pro! ide an efficient means of resisting such lnrsinn. Torsion is resisted bv both wa&ine &d uniform shear. Particular care must be tnken during com- . - - purer modeling of boxed shear ud l s lo reflect penetrations forelevator and stair doon. Cal- culation of incltiv based on a reduced uall thichess, depending on the number of shear wdl nenemtions. is common. Boxed shcar wall systems &e very well suited to regular plan - . oMice buildings. as demonsmled in many of ale project examples in this section. Con- slruclion advanwges ofr<infomed concrele shear uall systems include the following:

1. Central-services core shear walls can be efficiently constructed using slip-form orjump-form techniques. In the case of 120 Collins Skeet, a 4%-day cycle was achieved, ensuring that core wall construction was well off the critical path.

2. High-strength concrete hns enabled wall thicknesses to be minimized, hence maximizing rentable floor space.

3. Technology exists to pump and place high-strength concrete at high elevntions.

4. Fire rating for service and passenger elevator shafts is achieved by simply placing concrete of a determined thickness.

5. The need for com~lex boltcd or site-welded steel connections is avoided.

6. Wcll-detailed reinforced concrete will develop about twice as much damping as , structural steel. This is an advantage where acceleration serviceability is a critical limit state, or for ultimate limit state dcsign in earthquake-prone areas.

Although thcse advantages make concrete shear wall systems a compclitive construction method, the following must also be considered:

1. Shear walls formed around elevator and service risers require a concenvation of openings at ground level where stresses are critical.

2. Torsional and flexural rigidity is affected significantly by the number and size of oocnines around the she& wails throuehout the heieht of the buildine. . -

3. In 1 and 2 it is difficult to gauge the effect of openLgs precisely wilhout undertnk- ing time-consuming finite-element analysis.

4. Shear wall vertical movements will continue throughout the life of the building. n ~ e ~ r impact on the integrity o f ih r sIructure nlust b;rvalu31rd at the design slag;.

5. Consuruclion lime is gsnerally slou,er I I I ~ for n sleel-framed building. 6. The additional ueirhl of the \er~ical concrete elemcnts as compared to steel will in- -

duce a cost penalty for the foundations. 7. An incrense in mass will cause a decrease in nntural frequency and hence will mast

likely produce an adverse effect of the acceleration response depending on the he- quency range of the building. But shear wall systems are usually stiff and cause a compensating increase in nntuml frequency.

8. There are problems nssocialed with moving formwork systems, including the following: a. A sienificant time lae will occur between footinc construction and wall construction u -

beenuse ofthe fabrication and ureclion on rile ofthe moving formwork system. O. Time will be lost at levels !s,hcru aalls are lerminatcd or decrrased in thickness. c. Reeular survcv checks must he undertxken to ensure that the vertical and twist ~ ~

xlignmcnrs of the s h r x walls are uithin tolerance. d. In pneral it is difficult ru achieve a good finish from slip-form formwork sys-

tems, and hence rendering or sollle other Ispc of finishing may be necessary. E. When walls IW 100 thin [such 3s 150 iIlnt(6 in.)] it is not unusual for friction be-

trrccn ~ h c forms and cuncrcle lo lift lflr concrcle in slip-form conatmction. Icad- ing to cracks or gsping holes in the wall.

Sect. 4.21 Shear Wall Systems 111

"i; $& .g Project Descriptions 1: ,g;.: '#: ,'p

Metropolitan Tower :#; New York, N.Y., USA .s, @. Architect g! 'rn. .*; ':c ~.* .&. ,I:: Structural engineer ,p :l Year of completion i .. Height from streel lo roof

Number of stories Number of levels below ground Building use


Basic wind velocity Maximum lalcral deflection

Design fundamenlal period

Design accclererion Dcsign damping Earthquake loading Type ofslmclure



Story height

Beams

Beam depth Slab Material

Columns Material

Core

Material

Schuman. Lichtenstein. Claman and Efron with design input from MackboweIDenmanl Werdiger Robert Rosenwasser Associatcs P.C. 1985 21810 (716 it)

68 2

Office lo 18th floor; residential above Concrete

2.5 P a (50 psi) office; 2 Wa (40 psi) residential 47 d s e c (105 mph), 100-yr return

HI500

5 and 4 sec horizontal; 2 see torsion I5 mg peak

1 2 % servic~ability; 2%% ullimatc Not applicable Coupled shcar walls plus perimeter frames

Rock. 4-MPa (40-tonlit') capacity

Spread footings

3.45 m (I l ft 4 in.) office: 2.95 m (9 ft 8 in.) residential

Span and spacing vary 508 mm (20 in.) at perimeter

216-mm (8.5-in.) flat slab Concrete, 42 to 28 MPa (6000 lo 4000 psi)

Size and spacing vary Concrete. 58 to 39 MPa (8300 to 5600 psi)

Coupled shear walls: thickness varies

Concrete, 58 lo 39 MPa (8300 to 5600 psi)

A rectangular towcr \vould not work because of restrictions on the north-south-oriented site. This problem was solved with a triangular tower whose longest face is oriented northeast, with setbacks designed to conform to zoning regulations. The L-shaped commercial base is 18 stories, whereas the upper trianeular condominium towcr is 46 sto- . . rits p l ~ s l au sluiies iur IllL. 1nec11:~nical and stn~cu!rai Iransiiion. 'l'hr. Iksding edge of lhu Inangular lower being north on 57th S1rcr.l 1s continued for lhc enure 21X.m 1716-11) Ihti~bI of the bull din^. inlcgrating thu 1r.o b ~ s i c iorms. In !his way lhl: unique lrilneu- - - - lar Yower mximizes one of its greatest assets-the views (Fig. 4.43).

FIR. 4.43 hlclrupulilun T u ~ e r , NPW York. (Coi,ncr). o~RobenRarmm~nsrcrA.~rucl

112


The uooer condominium tower contains 246 luxurv apartments tolaline 39.300 mz ~ ..

(423.000 ft'). The lower commcrci~l base has 21.000~"(2?5.000 ft') of;ental office space and 460 m' (5000 it2) for relail rental. The lotal project amuunls lo 60.600 m' (653.000 11') and required approximately 23.000 m' (30,000 yd') of concrete and 3300 tonnus (366-3 tons) of reinforcing steel. To keep an efficient column grid on tlte commcr- cia1 floors, a double-height reinforced concrete mechanical floor was crcned at the nine- teenth floor to allow thetransfer of loads from the triangular plan ofthe building's upper tower to its L-shaped base (Fig. 4.440). In effect this was a new foundation for the triangular tower, accomplished by using an exlmordlnaiy volume of concrete, an unusually dense mass of reinforcing stvel. and bcams up to 4 m (13 it) deeq. Thesc transfer girdcrs ucre c a t in two stages. the bottom 600 to 900 mm (2 to 3 it) belng cast first to s e n c as suooort for the remainder of the concrete in the second placemenL . .

The depth of the meandering shear wall (the main btmctura~ support of the triangular footprint) is about 21 m (70 ft) (Fig. 4.446). 0: the three available faces. the west face was a lot-line face. and therefore obloce to accommodate the elevator shafts for the high-rise structure. It was recognized, and later verified in a wind tunnel tcst, that the structure would support larger wind forces acting perpendicular to the hypotenuse of the trianele. -

Vnncx rhedding, u,hich ~lsually pruduces larger forces ironsverse tn ths wind dirdc- lion, did not matcriallzc for this structure bscausc of its triangul:lr foulpnnt. Shear walls then migrate from the west lot line, meandering alongside the apartment lobby and corridors, to the hypotenuse side of thc triangle, where additional columns were engaged via Vierendeel action of the spandrel beams. Other frame elements. 508-mm (20-in.)- deeo soandrel beams alone the oerioherv and 216-mm (8.5-in.) slabs at the interior of . . . . . the structure, were needed to help counter large torsional loads since it was impossible to minimize torsional forces for all possible wind directions. This slender lower was somewhat stiffened bv a wider bascbelow the eiehteenth floor. However, part of the shear tva11 and nlany of the columns bad to bc transferred utilir~ng dsep concrets girders nt this levcl. These deep girders w r r . utilized. via outrigger action, lo ungxgc nddl- tional supports to help d ives hold-down loads for the shear wall and to equalize the strain in the supports.

The flat slab floors are supported by a hybrid building frame of columns and shear walls. in purt because of the developer's desire to leave the perimeter as column-free as possible.'~n the triangular tower. \\;ind on the long side of ;he triangle governs the dcsign, so the shear walls were placed at right angles to that face of the building, mean- derine alone partition lines in a horseshoe shape to the opposite side o f the tower and hackio theidne side of the trianele.

b

Scveml factors contributed to the decision to use concrete rather than steel. Thesc included the easier modeling oishapes. the ability to make last-minute changes, and the knowledre that a lareer miss reduces vibration and the perception of motion. The choice - . . ofconcrute raflucls ths needs ofthe u\tremi.ly ?all slel~dsr struclurc S\ray ofthe huilding uas an impnnanl uunccm. In high-nsc hu~ld~ngs i t may range from 11500 tn 1/600 of the buildine hcieht in a lUU-\u~r wind (tl13t is. thc slronwst uind lhilt inns bi. :~aticipatcJ lo occur in a 160-"car oeridd). When comoarine buildiks of structural steel and reinforced

d A . u

concrele having similar stiffnesses and movcmenlr. the perceived motion in the concrete building will be less bccausc the larger mass of the concrclc structure slows do\isn its swayini motions, that is, the period isincreased and the accclcration reduced.

In the Metropolitan Tower the typical slab floor thickness of 216 mni (8.5 in.) of stone concretc is important in achieving the mass of t h e building. Nevertheless, the huildine was designed with provisions lo support the \vcieht o f a pcndulum-type dnmper - - . . - . . should it be needed. Using thrcc nccclcrometers, field measurements wcrc tekcn when the structure reached its fifty-fourth floor and, latcron, at its sirty-sixth floor (at the last


possible date, allowing time for a "galno go" decision with regard to the installation of a damper), indicating that adamper was not needed. Theexlra cost to the owner resulted from orovidine a double desien lavout, with and wilhout lhe damper. No materials, ex- ~ - - . cept those nrcded to support the damper's weight on the footings 2nd columnr. were oc- tually expended in the svucturz. This suucture can accommodate a future damper, if found necessarv durine its service liir, with some nunor modifications and rerouting of - some mechanical pipes.

Slab formwork was cycled by the "preshoring" method commonly used in New York (Grossman, 1990). The first 18 stories, larger in floor area, were completed at the rate of about 4 to 5 days per story. In the triangular tower, two floors per week was typical progress, with columns and shear walls cast on Mondays and Thursdays and floors on Tuesdays and Fridays. Near the top of the tower, work speeded up to 2 days per story. The concrete framewas topped out on October 2. 1985

(4 Fig. 4.44 hlctrnpulllnn Tuscr. to1 L-sllupcd borc. ( b ) hleundrringshcor ,,,,11.

114

Lateral Load Resisting Systems [Chap. 4 Shearwail Systems

Embassy Suites Hotel New York, N.Y., USA

Architect

Structural engineer

Year of completion Height from street to roof Number of stories Number of levels below ground Building use

Frame material


Basic wind velocity Maximum lateral deflection Design fundamental period

Design accclerstion Design damping

Earthquake loading Type of structure


Story hrigllt

Columns

Fox and Fowie Architecls

DeSimone, Chaplin and Dobryn

1990 146.3 m (480 it) 46

I

Hotel

Concrete above 8th floor: concrcte-encased steel below

2 kPa (40 psQ 36 mlscc (80 mph)

Hl.150, HI700 5.4.7.4 sec

21 mg peak 2% serviceability

Z = 0.375; C = 0.030 and 0.025; K = 1.0

Shear walls above 8th floor; encased-steel trsnsfer trusscs to steel supercoiumns be- IO\V Rock. 4-MPa (40-tonlft') capacity Concrete piers

2.65 m (8 fi 8.5 in.) 200-mm (6-in.) flat plate, spanning 7.32 by 7.32 m (24 by 24 R) 4 supercolumns built up from five 200- rnm Win.) plates on 14.63- by 39.63-m (48- by 130-ft) grid

Core Shear walls. 300 to 450 mm (12 to I8 in.) thick at ground floor

Material 56-hlPn (8000-psi) concrete

1568 Brondway is the site ofthe Embassy Suites Hotel in the Times Square district of New York Cily (Fig. 1.45). I t is built over the historic Palace Theatre, a landmark dating back to 1919. Bccausc of the theater's landmark status, New York City would not permit any disturbance to tbc theater by the new hotel. It was therefore necessary to suppon this 46-story. 146-m (480-TI)-tall building by building e "bridge" over the theeter [Fig. 1.46).

The transfer was accomplished with a hybrid composite steel and concrete structure consisting oftn,o 40-m (1.X-f11-lung compnsile trusses and steel cross trusses. Four su- perculun~ns. two on either side ofthe theater, come down to ground to suppon the structure. Thcsc columns n'erc built up out to thick grsde 350-hIPa (50-ksi) steel plates and n'eigh up tu 6000 kg/m (4000 lhlfl). The truss menlhers were dcsi~ned to bc light enough to pern~it erection on an estremcly diflicuit site. To give them the necessary stiffness, the

entire wsses were encased in concrete. The ballrooms, kivhen, and mechanical spaces are located between the 14.9-111 (49-ft)-high trusses. The system is efficient and economical and solved the problems associated with constructing over a landmark.

The hotel superstructure is a reinforced concrete flat-plate system with a 8.5- by 8.5- m (28- by 28-it) column grid and was built on a Zday cycle. Wind is resisted by shear walls ns well as moment fnme acdon of slab strips and columns. The total weight of the reinforcing steel used for the concrcte tower was only 36.7 kglm- (7.5 pSO.

Fig. 4.45 Emburry Suilcs Hotcl. Nss York.


Fig. 4.46 "Bridgc" rupportlng hotel over thcotcr. Embnsry Suits Hotel.


Singapore Treasury Building Singapore

Architect Swctural engineer

Year of completion Height From sueet to roof


Building use Frame material Typical floor live load

Basic wind velocity Design fundamental period

Design acceleration

Design damping Eanhquake loading

Type of structure


Footing type

Typical floor

Story height

Beams

Beam depth

Columns

Core

Material

Hugh Stubbins and Associates

LeMessurier Consultants with Ove Amp and Partners

1986 234 m (768 fl)

52 5 office Concrete core, steel floor beams 2.5 Wa (50 psf) 30th floor and above: 3.0 kPa (60 psf) below 30th Floor

38 mlsec (85 mph)

5.6 sec Not estimated ~ p p r o x 2% serviceability

Not applicable steel floor beams cantilevered off cylindrical concrete core wall

Clay over rock 6 8.m (26-ft 3-in.)-diamctcr caissons. 35

(I 1 5 ft) long, under a 2.9-m (9-ft 6-in.)- thick mat

4.25 m (13 ft 11 in.) Cantilever 11.58 m (38 fr), spacing 4.9 m (16.42 ft) at core 1470 mm (58 in.). facade w s s 1260 mm (50 in.) deep, continuous 80 mm (3.25 in.) on 77-mm (3-in.) steel deck only erection columns embedded in core wall Reinforced concrete cylinder. 22.95-m ( 7 5 4 ) I.D., 1.65 to I m (65 to 39 in.) thick

Concrete cube. 40 to 30 MPa (4500 3400 psi)

This cylindrical 48.4-m (I 59-Ft)-diameter mixed construction office lower, loca!ed in the center of Singapore, has an area of more than 132,000 m' (1.42 million h') (FIE. 4:-17). Although the Singapore wind climate is relatively benign, avoidance of resonsnt vlbra- tion caused by wind-induced vortex shedding conlrolled the required latcral stlffness Of

the tower. This required setting the first vibralion mode period at no more than 5.6 set.


The architect and owner wanted to have little or no visible StNCtUre obstructing the 360" panoramic swcep u l the \vinduu,s at each floor. The simple jet elegnnl structural solution was lo cantiicvsr evcry floor from an inner cylindrical wall enclosing tile clc- 1,3101 and service core. This required radial beams ubich cantliever I 1 6 m (38 h) from the 24.95-m (81.8-ft)-outside-diameter reinforced concrele core wall. Each cantilever girder is welded to a steel erection column embedded in the core wall (Fig. 4.48). The cantilevers on successive floors are connected at their outer ends by 25- by 100-mm (1- by 4-in.) steel ties, hidden in the curtain wall, which reduce relative vertical deflections

Fig. 4.47 Singuporc Treasury Dullding. Singnpurc. ICounerj olT11ile Sr.libi,n r\.~saciorion.)

I Sect. 4.21 Shear Wall Systems

of adiacent floors. A stiff continuous nerimeter rine truss at each floor minimizes rela- 1 - live deflcc[ions of adjacent cantilevers on the same floor pruduced hy any unrvrn live loading. This w s s plus the rrnical tier also provide some redundancy in the unlikely 1

3 event of a cantileve; failing. $;,: All gravity load and all the wind loads are resisted by the concrele core wall. For . strength alone, the core wall would have been a constant thickness almost to ground

@j . > f S , ' ' .level, bur in order to meet the building period limitation, it was necessaq to thicken the :T wall from its typical 1.0-m (3.3-fl) dimension lo 1.2 m (4 ft) and then 1.65 m (5.4 ft) he- @ .,.. ... low the sixteenth floor. A concrete core wall was selected in lieu of an all-steel diago- $: :q

b Fg. 4.48 Typicnl noor plan; Singopore Tmsury Dullding.


nally braced "wall" for reasons of economy. The core is spanned by two plate girders. ~ h h c o r e wall has four doorway openings on each floor. The headers over these openings consist of rigid steel Vierendeel girders, which allow duct work to pass lhrough (Fig. 1.19).

Structural steel floor framing was used to facilitate a modular electrified underfloor steel deck, including trench headers, and to make the long cantilevers quite stiff. Typi- cal live-load deflection at the end of the cantilever was less than 25 mm ( I in.). Girders were cambered to countcnct dead-load deflection. Web openings were provided in the cantilevers for ducts and nines. To vcrifv the dcsirn and fabrication oualitv and reassure . . - . , theowner that deflections would not be excessive, a full-size prolotype cantilever girder welded to a two-story steel column was tested at the steel fabricator's laboratory in laoan. Thc test was ouite successful and verified the accuracv of the structural analvsis within a few percent This ,&as lhc first significallt slcel-iromed building lo bs built In Sing;.purr.. m the ICSI u.ns also hulpful in pruviding arsurnncc to the huilding ullisials of the competence of the design and steel construction team.

Because of the somewhat unusual s t ~ c l u r a l framinr svslem. the concrete core wall & . WAS designed conscn,alivcly lo rusisl porciblc, slthuugh very unlikely, p;.tlurn lise l o x - incr i n srhicb scrersl cons~.cutire floors had live lnods i n ccrlain quxlraols and no l i \c load in others. The result of such loadinr oatterns was to induce throueh-thickness bend- -. - ing stresses in the wall due to these asymmetrical forces. The core wall was anslyzcd using detailed finite-element analyses. and reinforcing stcel was provided to resist !he in-plane and through-thickness forces and bending moments due to gravity loads with and without wind loads.

M Fig. 4.49 Framing perspective; Singopare Trensury Bullding.

123


77 West Wacker Drive Chicago, Illinois, USA

Architect ' Richard BofiillDeSteiano and Goettsch

Structural engineer Cohen-Barreto-Marchcrtas, Inc. Year of completion 1992

Height from street to roof 203.6 m (668 ft) Number of stories 50

Number of levels below ground 2 Building use Office

Frame material Concrete core, steel perimeter Typical floor live load 2.5 kPa'(5O ps0 Basic wind velocity Chicago building code Maximum lateral deflection Less than HI500 Design fundamental period 6.67.5.88 sec horizontal; 6.67 sec torsion Design acceleration 29 mg pesk

Design damping 2% serviceability Earthqunkc loading Not applicable Type of strucmrc Cnncrete shear core, perimctcr stcel

frames Foundation conditions Hardpan, 1700-kPa (40.000-ps0 capacity Footing type 21-m (70-it)-deep caissons. 900- to 3000-

mm (3- to 10-11) shaft diameter bcllcd to 1370 to 7000 mm (1.5 to 23 it)

Typical floor

Story height 3.96 m (13 ft 9 in.) Beam span 13.72 m (45 11) Beam depth 533 mm (21 in.) Beam spacing 3.43 m (I l ft 3 in.) Material Steel Slab 110-mm (5.5-in.) concrete on metal deck

Columns

Sire at ground floor W350 X 1086 ( W i 4 X 730) plated Column spacing 3 m (10 ft) min. 13.7 m (45 it) max h4atcrial Steel. F, = 350 MPo (50 ksi)

Core Central concrew shear core Wall thickness at ground floor 559 and 355 mm (22 and 14 in.) Matcrial Concrete. 52 to 35 MPa (7500 to 5000 psi)

This 50-story 96.600-m' (1,040,000-TI') office torver is located at the southwest corner of Wacker Drive and Clark Street (Fig. 4.50). It is a classically styled addition to the Chici~no skyline on North \\'ackcr Drive. which is graced by several outstnnding architectural and structural originals. I Fig.450 77 West Wnckcr Drivc. Chicago, lllinuir.


The building. which is rectangular in shape. 50.29 by 42.67 m (165 by 140 ft) with 4.57-m (15-R) reentrant angles at the four corners, is the first high-rise tower designed by the Spanish architect, Ricardo Bofill. It was designed in collabontion with the Chicago architectural firm of DeStefano and Partners.

The framing system is a central concrete core surrounded by a structural steel h m e with a composite floor deck (Fig. 4.51). The core, which is extremely slender [ I 5 5 5 by 27.45 m (51 by 90 ft) with a height-to-width ratio greater than 13:1] incorporates all the mechanical, electrical, and verticnl transportation amenities. The column-free floor spans allow for a very flexible 13.72-m (45-ft)-wide tenant soace.

Another outstanding feature in the building is its magnificent entrance lobby, which extends from the ground to the fiflh floor, with a completely unobstructed space of 50.29 by 13.72 m (165 by 45 it). 13.72 m (45 it) high.

Fig. 4.51 hlidrise noor framing plnn, l l d to 36th floors; 77 Wesl Wneker Drive.

Shearwall Systems Sect. 4.21 127

Casselden Place Melbourne, Australia

Architect Australian Conswction Services with Hassell Architects

S INCIUI~~ engineer Connell Wagner

Year of completion 1992 Height from street to roof 160 m (525 ft)

Number of stories 43 Number of levels below ground 3

Building use Office Frome material Concrete core, steel frame

Typical floor live load 4 kPa (80 psfl

Basic wind velocity 41 mlsec (92 mph). 50-yr return

Maximum lateral deflection 150 mm (6 in.). 1000-yr return

Design iundemenlal period 3.45.5.00 scc Design acceleration 4.5 mg rms. 5-yr return

Design damping 1% serviceability; 5% ultimate

Earthquake loading Not applicable

Type of structure Core for all lateral load

Foundation conditions Siltstone. 2-MPa (20-ton/ft2) capacity

Footing type Pad footings Typical noor

Story height 3.75 m (12 f t 4 in.)

Bcam span I 2 m (39 R 4 in.)

Beam depth 610 mm (24 in.)

Beam spacing 3 m (9.83 it1

Slab 130 mm (5 in.) on metal deck

Columns Size at ground noor 950-mm (37-in.)-diameter composite con-

crete-filled steel tubes

Material Concrete, 70 MPa (10.000 psi)

Core Concrete shear walls. 500 and 200 mm (22 and 8 in.) thick at ground floor

Material Concrete, 70 MPa (10,000 psi)

This building is interesting for several reasons:

1. Construction over Melbourne underground rail loop 2. Use of high-sbenglh concrete

3. Use of composite concrctc-filled steel-tube columns

~h~ conswctian of Casselden place (Fig. 4.52) orrcr the Melbourne underground rail loop necessitated two unusual design features. (])The removal of rock for the three-


Fig. 4-52 Cmscldcn Place, hlelbourne, rlunrn)jn.

If Sec t 4.21 Shear Wail Systems

story basement rclnxed the overburden pressure on the tunnels. (2) To prevent heaving of the tunnels, 26 30-tonne (33-Ion) vertical anchors were inslalled to Lie the tunnels down. In the areas where only l i ~ h t loads were reimposed, there anchors are permanent. 1 but where heavy loads are imposed by the new struch~re, temporary anchor; only were used. In addition, piling was used in some areas to provide load transfer to below the \ level of the tunnels in the event of ground movement

The mosl inluresting pan of the c~nstruction is the columns construction. Thts method is the firs1 of i n type in Austrnlia. with only a small number of buildtngs knnwn lo b: constructed using similar methods anywhere in the world. The tube columns are erected - in two-slory lifrc, wilh (he bare steel able ro suppon up to six stories of construction. Con- crete is p~mped into the b;lse ofthe lube, and up as man) as six slories at a lime. No 1% bmtinn of the concrele is required. Conncll \'fagner ha.. dcveluped design methods for

1 this tjpc of column. including lltc use of thin-walled lubes. No codified mclhod for rhe design of thin-walled concrete-filled lubes is av~ilable anywhere in the world. !i

This form of construction orovides a column for a steel-fmmine svstem at a cost \f ~~- - . equal to that of a reinforced concrete column. The cost of the columns has been a major stumbling block in the economies of steel-framed buildings, with the penalty for using all-steel columns on a building such as this as high as 3% of the total building value- millions of dollars on projccls of this size. This solution benefils from the economy of concrete. with the simple concrele placement method giving the system constructabilily lhal ir couivalent lo that of a full sicel column.

-

~ ~. 'llie cure and columns on llic project use concrete olup lo 70 hlPa (10.000 psi). T ~ L

culuinns arc considcr:d to bc an ideal u.3). raluring br~h-slrcnglh roncrele of good cur- ing ability, which is being placed inside btube. ~ h c tube confines the concrete, enhancing the ductilily of the high-strength materials. I


Twin 21 Osaka, Japan

Architect Nikken Sekkei Ltd.

Smctural engineer Nikken Sekkei Ltd. Year of completion 1986 Height from street to roof 157 m (515 ft)'


Building use Office, shops, showrooms Frame material Steel core and perimeter on upper floors:

concrete core and concrete-encased steel perimeter on lower floors

Typical floor live load 3 kPa (60 psO

Basic wind velocity 35 rnlsec (78 mph) Maximum lateral deflection 400 mm (16 in.)

Design fundamental period 3.9, 4.0 scc Design velocity 250 mmlsec (10 in./sec) for medium

earthquakes: 500 mmlsec (20 in./sec) for maximum-level earthquakes

Design damping 270 Earthquake loading C = 0.10 Type of structure Primarily perimaer rigid moment frames Foundation conditions Clay

Footing type 18-m (59-(1)-long. 1.5- to 2-m (5- lo 6.5- ft) shaft-diameter belled concrete piles

Typical floor

Story height 3.75 m (I? f t 4 in.)


Beam depth 820 mm (32 in.)

Beam spacing 3.2 m ( I0 ft 6 in.)

Material Steel, grade SS 400 and SM 490 Slab 165-mm (6.5-in.) concrete on metal deck

Columns Size at ground floor 1400 mm (55 in.)

Spacing 6.4 and 12.8 m (21 and 42 it)

hlatcrial RcinSorced concrete and structural steel Core Reinforced concrete lower levels: steel

upper levels

Thickness at ground floor 700 to 900 mm (27 lo 35 in.)

Twin 21 comprises t\vo identical 38-story office towers with sbaps and showroom.; on the lowcr floors (Fig. 4.53). The perimeter frames above the sixth floor have columns


spaced at 3.2-m (10-ft 6-in.) inten,nls, connected by the floor slabr to the slucl-fmnlcd core. This suucture is eflicient in resisting horizontnl 2nd torsional deformations due to earthquakes and wind.

Below the sixlh floor the building smcture consiss of steel frames encased in reinforced concrete, and rigidity is provided by reinforced concrete shear walls around the core. The majority of the horizontal force is borne by these shear walls (Fig. 4.54).

Had the tower building columns been continued down through the low-rise section at 3.2-m (10-ft 6-in.) centers, space utilization would have been adversely affected. Hence the 3.2-m (10-ft 6-in.) spans are increased to 12.4-m (40-8 8-in.) soans bv one- . . , -

story-high concrelc-encased ste.el transfer beams at the fifth-ljoor level, thereby pro\,iding for shops and showrooms in the lou,rr floors of the building.

The uind load response due to the tuin towers bcinr in close proxim~tv *,as checked using wind tunnel testing and the results were reflectea in the design.

The atrium of the low-rise pnrt is surrounded by the low-rise parts of the two towers and the gallery building (four stories wilh an L-shaped floor plan). It is composed of a large space [about 47 by 47 m (156 by 156 ft)] nod is covered by alarge steel-pipe space buss roof suucture.

There are large forces on the roof due to the uplift of the wind blowing between the twin towers and the down wash off the buildings.These factors were evaluated by wind tunnel testing.

The atrium roof trusses are supported on slide bearings, which can absorb horizontal deformations of the high-rise part during an earthquake. Stoppers are provided to prevent uplift under upward wind loading.

Elg.453 Twin 21. Osoko. Jopon.

Lateral Load Resisting Systems [Chap. 4 Sec t 4.21 Shear Wall Systems 133 1 :q 5' Majestic Building ,@i, .@/: Wellington, New Zealand E. , Architect Manning and Associates

Structural engineer Wass Buller and Associates . . .:,:Year of completion 1991

Height from street to roof 116 m (380 ft)

Number of stories . 29 I, . . .


Office Building use

Frame material Concrete Typical floor live load 3.5 kPa (70 ps0

Basic wind velocity 50 d s e c (112 mph)

Design fundamental period 2.9 sec Design acceleration 10 mg peak, I-yr return period . Design damping 1% serviceability (wind). 5% EQ

Earthquake loading C, = 0.0132

Type of structure Core and perimeter frame

Foundation conditions Weathered rock over rock

Footing type Pads and 1.8-m (6-ft)-diameter bored piles

Typical floor


Beam span 12 m (39 f t 4 in.)

Beam depth 750 mm (29.5 in.)

Beam spacing 10 m (32 ft 10 in.)

Slab 365 mm (14 in.) Dycore Fig. 4.54 Typimlstrurhrnl floor plan; sin 21.

Columns Size at ground level 1400-mm (55-in.)-diameter

Spacing 10 m (32 ft 10 in.)

Material Concrete. 50 MPa (7100 psi)

Core Thickness at ground level 400 and 600 mm (16 and 24 in.)

Material Concrete, 50 MPa (7100 psi) max

The Majestic Building (Fig. 4.55) comprises 32 levels tolnling 42,000 m' (452.000 it'). including four levels of parking garage, extensive retail, arcade, and public plaza areas. a fitness center with a 33- by 4.5-m (1 10- by 15-ft) swimming pool, a crkche, an art gallery. and approximately 24.000 m' (258.000 it2) of office space.

Wind engineering played a major part in determining the building shape, podium features, and strucmre of the building. Three separate wind tunnel studies were undertaken to investigate environmental wind effects, cladding pressures, as well as overturning moments and acceleration levels. Following completion, further studies of the


structure were cnrried out usinf: a mechanical vibrator and also recording wind dis- - placumenls using scnsili\,c occelcromclers.

The building is located in the most active c ismic zone of Sew Zeal;~nd, with knoun fault lines running lhrouyh the ccnlral business dislricl of \Veilinglon. The first floor of the tower is I2 m (40 fl) above street letel and the column spacing around the perimeter i s !O m (33 fl). These fentures were critical to crtnlc a spncmus lobby and enlrancc to the building; however, such features in seismic zones require special design to prevent the occurrence of a "soft story." For these reasons a "ductile hybrid structure" was chosen as the lnleral load resisting system. The concrete core walls and the perimeter frame work together and were designed using capacity design methods lo be fully ductile. Foundations and lower levels were designed to resist the overslreneth capacity ~ ~ ~ - . - - . . . forces from the superstructure.

The unique floor system comprises prelensioned hollow core planks 1200 mm (4 fl) wide and 300 mm (12 in.) deee, seaced at 2400-mm (8-ft) centers. A thin metal may was . . plscud hctaccn lllc hollow core planks, and 65 mm (2.5-in.) of in-situ cuncrele ~ 3 s placed over the whole floor.Tlrc floor is only 115 mm 1.1.5 in.) dccp in parts, uhich nl- lous for~ff ic1~111 duct I ~ ) O U I S . I t neighs only 3.6 kPa (75 psQ and can suppurl in excess of 3.5 P a (73 psf) overi2.5-m (41-fl) spans (Fig. 4.56).

Sect. 4.21 Shear Wall Systems

[Chap. 4 Sect. 4.21 Lateral Load Resisting Systems Shear Wall Systems 137 I Telecom Corporate Building Melbourne, Australia

Architect S l ~ c t ~ r a l engineer

" Year of completion

Height from street to roof

Number of stories


Building use


Basic wind velocity



Design acceleration Design damping

Earthquake loading

Type ofstructurc

Foundalion conditions Footing type Typical floor

Story height Beam span

Beam depth Beam spacing

Material Slabs

Columns Size to ground floor Spacing Material

Core Thickness at ground floor Material

Perrott Lyon Mathieson I

Connell Wagner 1992

192 m (630 ft) , ~,..

47 . ... ....* ~ . .

3

Offices

Concrete

4 kPa (80 psO

41 mtsec (92 mph). 50-yr return 123 mm (5 in.) at 25 mm (1 in.), 1 return 4.5 sec

4.4 mg rms, 5-yr return

1% scrviceability; 5% ultimatc !,J@ Not applicable ,$# Concrete core and perimeter lrame tube~a tube @!'

,:%I*:

..:,., Pads to columns. raft to core :.s::.

!stt

3.85 m (12 ft 8 in.)

12 m (39 ft 4 in.) 440 mm (16 in.)

5 m (16 f t 5 in.)

Partially preslressed concrete 125-mm (5-in.) reinforced concrete

1000 by 1200 mm (39 by 47 in.) 8.1 or 9 m (26 ft 7 in. or 29 ft 6 in.) Concrete. 60 MPa (8500 psi) Shear walls 500 and 200 mm (20 and 8 in.) Concrete. 60 MPa(8500 psi) mas

This all-concrete building achieved impressive conslruction times (Fig. 4.57). The entire 50-level concrete core was complclcd in 14 months, using a jump-form system. Typical cycle times for the core averaged 4 % days per floor.

Lateral Load Resisting Systems 'w:

[Chap. 4 I D Se.. 4.21 . *

The tower floor band beams. typically 400 mm (16 in.) deep. are notched to 275 mm (11 in.) thick at the core to allow the major mechanical ring duct to encroach into the structural depth, thereby reducing the floor-to-floor height.

The band beams were designed as ~Ktia l ly prestressed and are offset from the - . columns. A typical beam has three tendons. Two tendons, each with four 15.2-mm (0.6- in.)-diameter strands, were stressed from the external end of the beam. A single tendon

Shearwall Systems

with three 15.2-mm (0.6-in.) strands was tensioned from the opposite end. The bands were top-sucssed. Grinding in b ~ c k of the surface ofthe anchorage pockcs was no1 nrc- essary because access flooring is being provided throuphout the tower

One hundred percent of the prestrr5s force was appiisd to cach tendon u hen the concrcte had reached a strength of 22 hlPa (3 100 psi). Using a high early-strength concrete mix, this uas achieved on lhc second d3y after the pour. This, togeli~er with d ~ e use of two sets of table forms, alloued floor-to-noor cycles of three d3ys lo be achieved.

The tendons arrive on site prefabricated with suands already threaded into the ducts. The connection to the corc is ;imply and posili!,cly affected b; Ihe use of 600-mm (24- in.)-long 20-mm (0.75-in.) bars which wrap around the vertical rcinforcrme~~t in the core wall. The prrimeter spandrel beams are 775 mm (30.5 in.) deep by 350 mm (14 in.) wide, spanningup to 9 m 730 ft). Reinforcement cages for these biams were fabricated on construction decks on the podium roof and craned directly into position. Loose bars were added at column locations to provide continuity.

The main enlrance to the building is a dramatic three-story-high entry auium. The nerimcter of this alrium is elass on exoosed architectural steelwork fabricated from 250- by 250-mm (10- by IO-in.)-square hollow sections. This steciuork IS hunp from 3 2200- mm by 950.mm (86- by 37-in.) posrtensi~ncd cnntiicvcr ring beam at lcvel 3, giving the imnression of a glass cube susnendrd in midair. The rinc beam is clad !r ith 200-mm 18- - in.)-thick polished precast panels used as formwork.

The e n y space is further enhanced by the termination of one of the tower columns above the lobby level. The column load is 24,000 kN (2640 Ions). This is achieved using slage-stressed 3950- by 1000-mm (155- by 39-in.) posttensioned beams, each spanning 18 m (59 ft) in a cruciform la you^ The beams hove eight and six tendons, respec- tivelv. with 19 12.5-mm (0.5-in.)-diameter strands in each tendon. The beams are stressed in three stages as load from the tower is progressively applied, achieving essentially flat beams throughout the construction phase.

F~E. 4.57 Talccam Carpornte Building, Melbourne, Aurlmlio. (Pboro by S ~ U I T E P I I O I O ~ T O ~ I ~ I C I ) I

140 Lateral Load Resisting Systems IChap.4

4.3 CORE AND OUTRIGGER SYSTEMS

Whilc outriggers have only brcn incorporated into high-risc buildings nithin the last 25 veors. the o u v i g ~ e r as a structural rlcmenl has a much longer Itistn~y. The great sailing ;hias of the oastand nresent have used outriggers to help resist the wind forces in their .~ r- ~~ . -- sails, making the adoption'of tall and slendcr mas& porsible. In high-rise buildings lllc corc can be related to the marl of the ship, with rhe oulripger acting like the spreadrrj and the cxterior columns like the stavs or shrouds. The typical oreanization of a core and ~ . . - oulriggcr system is picturcd in Frg. 4.58. Just as in sailing ihipb. there outriggers serve 10 reduce the oven urn in^ moment in the core that would otherwise acl as a pure cantilever. and to transfer th; reduced moment to columns outside the core bv way o fa len- ...- - . ~~ - ~ . . siun-comprcssion couple, uhich takes ad\,antage of thc incrcascd momenl arm betu.cen these columns. In addition lo reducing the size of lhe marl. [lie presence of uutri:pers n l ~ n serves to reduce the critical conn~ction where the mast is sreoned to th? keel beam -~ ~- ~~~ . . In high-rise buildings this same bench1 is re3liz~d by a reduc~ion of !be hare core oter- turning moments and the associaled reduction in potential core uplill forces. Tlic same overtuLing moment which is taken through a couple between the windward stay and the mast to the pretensioned ties in sailing ships, is transferred to gravity-loaded precom- pressed columns in the high-rise building.

The structural elegance and efficiency of outriggers are well rooted in history. The outriggers have also becoine key elements in the efficient and economic design of high- rise buildings.

Sect. 4.31 Core and Outrigger Systems 141

1 Why Outriggers?

Modem high-rise buildings frequently incorporate central elevator cores along with generous column-free floor space between the core and the cxterior support columns. While this results in greater functional eficiencv. it also effectivelv disconnects the two ~~~~ ~~~~ ~ -~ ~~- ~ ~ . . major SWcNral elements available to resist the critical overturning forces present in a

.?';"Hieh-rise building. This uncoupling of the interior core and the perimeler frame reduces - - . - the overall rerislance of llte StNClUre lo the ovenurning forces lo the sum of llte inde- pcndcnt resisrances of the individual rlrmcnrs. The incorporation of outriggers in this Same svstem couales these two comonnents and enhances the system's abilihl lo resist overturning forces dmmatically.

For buildings of up to 35 lo 40 stories, reinforced concrete shear wall or steel- braced cores have been effectivelv utilized as the sole lateral load resisting svstem. - . These iystems are very effective in resisting the forces and associated deformations due lo shear racking since their resistance vnries approximately linearly with Lhe build- - ~. ine heieht. However. the resistance that core svstems alone arovide to the overlurnine u - -

component of drift decreases approximately with the cube of the height. so that such core syslems become progressively more inefficient as the height of the building increases. In addition toatiifness limitations. a core svstem alonican also eenerate ex- - cessi\u uplift forces in the core structure along with prohibitively high ovenurning forces in the building's foundation system. With !he sysrem's inability lo take adv;~n- ngr. oftlie overall building depth, designing for lhe resulting uplifl forces can be prob- lematic.

In reinforced concrete cores, excessive or impractical wall elements where large net tension forces exist can negate the inherent efficiency of concrete in compression resistance. In steel cores. large and costly field-bolted or -welded tension splices greatly reduce steel efficiency and the ease of fabrication and erection.

In the foundation system, these uplift forces can lead to the need for the following:

The addition of expensive and labor-intensive rock anchors lo an otherwise "simple" foundation alternative such as spread footings. Greatly enlarged mat dimensions and depths solely lo resist overturning forces. Time-consuming and costly rock sockets for caisson systems along with the need lo develop reinforcement throughout the complete caisson depth.

Expensive and intensive field-work connections at the interface between core and foundation. These connections can become particularly troublesome when one con- siders the difference in construction tolerances between foundation and core StNClUre.

n i e climinarion from consideration of foundation systems which might have bcen considerably less expensive. such as piles, solely for their innbilily lo rcsist significant uplift.

2 Outrigger Benefits

For many bnildines. the answer to the problems and restrictions of core-onlv or tnbulvr - struclures is the incorporation of one or rnorc lcvcla of oulriggers. Typical oulrigger organization consisls of linking the core o fa high-rise building to h e exterior columns on one or morc huildins faces with lruss or wall elements (Fig. 4.59). The outrierer sys- -- . tems may be iormcdin any combination of steel, concrere;or composite conswction. When properly and efficiently utilized, outriggers can provide the following structural and functional benefits to a building's overall design:


. Core overturning moments and their associated induced deformation can be reduced ~

tltrouglt ths "rc\r.r,c" momdnt applied to the cur< at each outrigger intersection (Fig. 1.60). This applies to titc core at r3ch outrigger intersection. This momtnt is created by the forcc couple in the exterior columns to which the outriggers connect. It can po- tentially increase the effective depth of the structural system from the core only to almost the complete building. Significant reduction and possibly the complete elimination of uplift and net tension forces throughout the columns and the foundalion system. . The exterior column spacing is not driven by structural considerations and can easily mesh with aesthetic and functional considerations. . Exterior framing can consist of "simple" beam and column framing without the need for rigid-framc-type conncctions, resulting in economies. For rectangular buildings, outriggers can engage the middle columns on the long faces of the building under the application of wind loads in the more critical direc-

Sect. 4 31 Core and Outrigger Systems 143

lion. In cure-;!lone and tuhuiar systcms. IIIL'SC columns which ;my siglliiicnltl gr;!v-

$, it! load nrs either not incorporntcd or ~nderutiiized: In aomc c3ser. oulrigsur s)stems 9. IF .,. can elficicntl\ lncomorate almost e\crv :rs\,ily column tnto !he laieral load rrsisrinc . - .

system, leading to significant economies.

3 Outrigger Drawbacks

The most significant drawback wilh the use of outrigger systems is their potcntiai interference with occupiable and rentable space. This obstacle can be minimized or in some cases eliminated by incorporation of any of the following approaches:

Locating outriggers in mechanical and inlerslitinl levels Locating outriggers in the naluml sloping lines of the building profile Incorporating multilevel single diagonal outriggcrs to minimizc the member's interference on any single ievcl

Skewing and offsetting outriggers in order to mesh with the functional layout of the floor space

. Uond Uuilding, Sgdnry, Austrnlin. Toncr bracing, ccsl-~wst lints, looking north. Fig. 4.60 1650 hlnrkcl Slrccl, I'hiludelphlu.


Aitolllcr potential drawback is the impact tile nutrigger isstallation cnn have un the crcctiun pruccss. As a typical building rrcction prouceda. the repelitlve nature of thc structurai framinr and th~reduetion in member sizes generally result in a learning curve which can speedbe process along. The incorporatioiof an outrigger at intermediate or uppcr levels can, if not approached propqrly, have a negative impact on the erection process. Several steps can be taken to mtnimtze this possibility.

. Provide clear and concise erection guidelines in the contract documents so that the erector can anticipate the constraints and limitations that the installation will impose. . If possible, avoid outrigger locations or design constmints that will require "backlnck- ing" in the consvuction process to install or connect the outrigger. The incorporation of intermediate outriccers in concrete construction orlarcc variations in dead-load column -- - suesses bctuccn the core and the exterior can in some cases result in the nccd to "back- unck." Such a need can be minimized if issues such >% creep and differential shoncning are carefully studied during the design process to minimize their impact. Avoid adding additional outrigger levels for borderline force or deflection control. Outriggers provide diminishing returns for each additional level added. Incorporate outriggers in less optimal numbers or locations when doing so will haven significant positive impact on the overall construction cosls.

Core and Outrigger Systems


g, Cityspire N e w York, N.Y., USA

- ,, , ; t ATehitect Mumhv Jahn . . Svuclural engineer Robert Rosenwasscr Associates


Height fromstreet to roof 248 m (814 ft) Number of stories 75

Number of levels below ground 2 Building use Office and residential

Frame material Concrete

Typical floor live load 2.5 and 2 W a (50 and 40 psO Basic wind velocity 47 mlsec (105 mph), 100-yr return Mnximum lateral deflection HI500

Design fundamental period 5.5,5.4 sec horizont;U; 2 sec torsion Design acceleration 15 mg peak. 10-yr return

Design damping 1 2 % serviceability; 2 2 % ultimate Earthquake loading Not applicable

Type of swcture Shear walls with outriggers at transfer levels and interior diagonals in olfice levels

Foundation conditions Rock. 4-MPa (40-ton/ft2) capacity Footing type Spread footings Typical floor

. . Story height 3.5 m (1 l ft 6 in.) office; 2.85. 2.95. 3.05

m (9 ft 4 in., 9 ft 8 in.. 10 ft) residential Beam span, spacing Vary

Beam depth 508 mm (20 in.) at perimeter Slab Flat slab Thickness 216 mm (8.5 in.) office; 241,267,305 mm

(9.5, 10.5, 12 in.) residential Columns Size and spacing vary

Material 56 MPa (8000 psi) Core Concrete walls of varying thickness

CitySpire. 156 West 561h Street, displaced Metropolitan Tower as the tallest concrete structure in New York CitySoncrctc placement reached to 244 m (800 it) and aluminum-dome fins extended the height to 248 m (814 ft) above grade. When completed in 1987, it was the second fallestconcrete structure in the world (Fig. 4.61). With a 1O:l ratio, it is the tallest, most slender structure (concrete or steel) in the world today. CitySpire has about 77.100 m2 (830.000 it') of floor space and required 33,000 m3 (43,000 yd3) of concrete and 4300 tonnes (4700 tons) of rcinforcing bars for its 77 construction levels (including mechanical and below-grade levels).


Floors 6 M 9

(a)

Floors 47-61

(4

Fig. 4.62 Floor plans; CitySpim.

S e c t 4.31 Core and Outrigger Systems 149 [Chap. 4

Floors 2645

(c)

;g: &?: &jj ,:.. .. , -:;

,@ .*, , Si, fl: ?g; 5 !a+ .- '8. :r 1! ,~,: a . ..

,I.. ;a: ,.a. :*,: 4f J" > I f

"L1. .- %,I >L? fr& i"i, x*': , '**

.:ST 3, ?db3 :t$q ;L.L ,rb: -@, -~. gY :r 7L.

Office

(4 Fig. 4.62 Floor plnm; CilySpire (Conrinurdl


Chifley Tower Sydney, Australia

Architect Structural engineer

Year o f completion Height from street to roof Number of stories Number of levels below grol Building use Frame material Typical floor live load Basic wind velocity



Design damping


Foundation conditions Footing typc

Typical noor

Story height

Beam span

Beam depth


Columns Material

Kohn. Pedersen. Fox with Travis Partners

Hack and Kurtz Australia with Thornton- Tomasetti 1992

215 m (705 ft) 50

~ n d 4

Office with 2 retail levels Steel 3 kPa (60 psO

50 mlsec (112 mph) ultimate, 1000-yr return

Hl400.50-yr return

5.0 sec 20 mg peak. 5-yr return, with operating tuned mass damper

7 lo 2.5% s~rviceability; 6% ultimate Not applicable

Steel perimeter frames, braced steel core with outriggers at levels 5, 29-30.42-43 Sandstone, 5-MPa (50-tonlft') capacity Spread footings plus rock anchors ilp to I8 m (60 it) long

4.075 m (13 ft 4 in.)

10 to I5 m (33 to 49 ft) 530 mm (21 in.)

2.5 to 3 m (8 ft 2 in. to 9 ft I0 in.) Steel, grade 350 MPa (50 ksi)

Braced steel frame Steel, grade 250 and 350 MPa (36 and 50 ksi) Rnccd steel frame. grade 350 MPa (50ksi)

Chiflcy To\+,er has been designed to house financial service organizations. Wiring needs were met by raised "computer" flooring, by generous riser closets, and by the open na- lure of a steel-framed core. (Less accessible concrete cores are most commonly used in Austmlia.) Steel rraming was also used to speed erection and occupancy (Fig. 4.63).

Its 90,000-m' (969.000-ft') tower rises from a 32.000-m' (345.000-11') full-site "podium." The building has a highly articulnted facade \+pith nonparallel sides, setbacks at different levels on different elevations, and a mix of flat, gently curved, and circular

core and Outrigger Systems 151

Sect. 4.31


faces. This desicn serves to define and enclose Chiflev Souare. reflect the street erid. u .

maximize the views ofharbor, park and ocean 1; the'north and east, break up the bulk ofthe tower, and enliven the Sydney skyline.

The numerous setbacks, the variety of facade geometries, and the desire for open views made a framed-tube shuctural solution impractical. A braced core would avoid involvement with the facade, but the tapered nature of the tower floor plans redulted in .',!$!.?$:' an inverted T-shape core plan (stepping back to an L at level 31) whose limited width would require unreasonably large columns to contra1 deflection (Fig. 4.64). To control deflections more efficiently, outriggers (or heavy trusses) link the core to perimeter columns at levels 5.29-30, and 42 (top) in the east-west direction and at levels 5 and 42 in the north-south direction. The middle east-west outriggers also serve as transfer trusses for a setback.

Sect. 4.31 Core and Outrigger SYStemS 153

The irregular building shape, irregular core geometry, and involvement of outriggers reouired analvzine and desienine the wind system structure by means of a complete . u - - three-dimensional computer model since no planes of symmetry exist and three-dimensional interaction was critical.

A oackaee of analvsis-and-desicn p r o g m s was developed for this projecL An in- . - - . - teractive deflection control routine determined "optimal" member areas to meet drift criteria by usinc virtual work establishing relative efficiencies of members, resizing the most effiiient members to meet deflection limits, and reanalyzing. A "final" analysis ...--~ ~~-

with optimal areas used precise loadings. Another analysis in;estigated dead loads ap- olied to the incomolete structure under consmction. '

A load combin;tion program look the member-force results of lllcse runs and appllcd forccs following an "overluming wind envelope" using directionalily from wind tunnel Icsts, sclected maximum and minimum wind forces for each member. and used combinations of the load cases lo dclermine maximum design forces for cnch mcmber. Wind allouablc suers incrrascs (force reductions) were included.

A member selection program used the "optimal" arcas. Ihe design forces, and a table of acceplahlc member sizes lo select a uial member size, with an arcathilt was near "up- limal," in order to check the load capacity in accordancc with the Auslralian stecl code AS 1250-198I.The loop was thcn repratcd with a larger trial size if necessary. Memhrr selection marks were piotted on diagrams of the core bracing for ease of use. Member forces were also plotted in various ways to aid in the design of connections.

It is inlerestine to note that ofice dead load plus reduced live load is about 20 lo 25% higher in ~ u s t m < n than in U.S. practice, so u ~ ~ p o l a l i n g U.S. lonnage figures lo Ass- tralinn projects could be m~sleading unless faclorcd up. Australian practicc also affecled the conslruction delails. Available hot-rolled member sizes me more limiled lhan i n the United Stntes. For floor bcams this mcant using a hunvicr size than onc might athcrwisc choose. As a result floors have a higher-than-minimum load capacily. For girders, built- un sections were common. Also, since t l~e available plate is 100 mm (4 in.) thick or less. &e largest column sections use flanges and web of doubled and tripled plates.

Chifley Tower includes a tuned mass damper (TMD) in the original consmction lo keep building movement below objectionable levels. Its help is not considered in the wind response for strength. The TMD mass is 400 tonnes (440 tons) of steel plate. suspended from eight 11-m (36-ft)-long cables anchored at level 46. Its period is adjusted by a tuning frame, which slides along the cables to vary their active length. Damping is provided by eight hydraulic cylinders which push fluid through a control valve and a heat exchanger in a closed circuit Movement is permitted in any lateral direction (NSEW), but torsion is restricted by an antiyaw yoke. The TMD is anticipated to increase damping from 1 to 2.5% and to decrease 5-yr acceleration from 0.03 to 0.02 g.


One Liberty Place Philadelphia, Pennsylvania, USA

Architect

Structural engtnccr Year of completion Height from street lo roof Number of stories Number of levels below ground


Typical floor live load Basic wind velocity

Maximum lateral deflcclion Design fundamental period Design acceleration

Design damping Earthquake l r ~ d i n g Type orstructure

Foundation conditions Footing type

Typical floor Story heiglll Bcam span Beam depth

Beam spacing

hlnterial

Slab

Columns Size at ground floor

Spacing Core

fvlateriol

Sect. 4.31 Core and Outrigger Systems 155 I Murphy Jahn

Thornton-Tomasctti Engineers

1988 288 m (945 it) 6 1

I Office Structural stcci-braced core with superdiagonal oulri:gcrs 2.5 kPa (50 psi) 3 1 mlscc (70 mph)

HI450 5.5 sec

15 111g pcak, 10-yr return I to 2% Nol applicable Braccd slccl core linked by steel girders to cxlerior columns

Rock. 4-hlPa (40-tonlf~') capacity Caissons

3.81 m (12 rt 6 in.) 13.4 m (44 rt) 530 mm (21 in.) 3.05 m ( I 0 rt)

Steel, grade 350 MPa (50 kst)

63-mm ( 3 - i n . ) concrete over 76-mm (3- in.) metal deck

W350 by 384 (W350 by 257) built up to 2788 kglm (1870 lb/ft) 6.1. 13.4.21.3 m(20.44 .70f t )

Linked braced frame with nutriggcrs Steel, grade 250-hlPa (36-ksi) hracing. grade 300-MPa (43-ksi) and 350-h,lPa (50-ksi) beams and columns

One Liberty Place at 288 m (945 11) is located on a prime block ofdowntorvn Philadel- phia (Fig. 4.65). The orlice floors range from 2230 m' (24.000 ft') in the lo\ver portions to 120 ni' (1300 it') at tllc pcak. The 61-story tower contains o\,er 120,000 m' (1.3 million ft') of floor area.

I Fig. 4.65 One Libcrty Piocq Philndclpinin, Pcnnrjlronio.


Structural steel framing was chosen for its flexibility and high strength-in particular, its ability to transmit large tensile and compressive forces efficiently while keeping the size of the members to a minimum. Built-up wide-flange sections were used for ail outrigger diagonals and core and outrigger columns due to the large forces and required thickness ofthe plates. Their use also facilitnted fabrication and erection.

~ ~

The typical floor framing consisU of composile W2I ASThl A-572 gmde 50 stecl beams spanning 13.4 m (44 it) from the building core to the cxterior face. As a result, thc cntire lease space within thc tower is column-free (Fig. 1.66). The structural slab is compuscd of a 76-mm (3-in.) composile decking with 64-mm (2.5-in.) stone concrete topping. Floor beams were cambered lo compensate for dead-load deflection under wet concrete placement.

The selected lateral load resisting system is a superdiagonal outrigger scheme composed of a 21.3- by 21.3-111 (70- by 7041) braced core coupled with six four-stom diaea- . -- nal oulriggers at each face of the core located at three points over the hcight of the building. The system works in a similar manner lo the mast of a sailboat, with the bncud core acting as the most and the outrigger superdi~gonnls and vcnicolr forming the spre.lder

- Fig. 4.66 Typical noor plan; Onc Liberty Plorc

Sect. 4.31 Core and Outrigger systems 157 I and shroud system. After various studies utilizing in-house optimization computer programs, three sets of eight outriggers were found to be the most efficient solution.

Although simplified models showed that they would be the most effective if spaced at equal intervals, optimization programs showed that these outriggers could further reduce wind-induced drift without addins additional steel by simply modifying their spac- ink o>erthel~cight of the building. ~ l t k a l e l ~ the design warc~mpleted with thr outside ends of tllc supcrdiagonnls placed at floors 20, 37, and 51. The outrigger supcrdiagonsls

I are connected'at theexteri& of the building to vertical outrigger columns. I

To reduce uplift forces on comer core Folumns and the ;itrigger columns it was desirable to concentrate most of the building's dead load on these columns. This was accomplished by introducing exterior transfer Wsses at floors 6,21, and 37, which span between the outrigger columns within the exterior face and thus funnel dead load, into the outrigger columns to compensate for uplift dueto wind pressure. Uplift in the exte- , ,,

nor outrigger columns was totally eliminated with this approach. The uplift on the corner core columns was reduced to 5800 kN (1,300,000 lb).

In developing the superdiagonal outrigger system, an intensive effort between the building's architects, interior planners, and developer was undertaken to determine that

$

the presence of diagonal outriggers penetrating down through certain lease space at eight locations on 12 floors would not interfere with theefficient layout of the space. In- terior planners made various layouts for full-floor and partial-floor tenants and concluded that the presence of the inclined superdiagonal columns would not hinder the real estate leaseability of these spaces.

Wind forces were generated using prevailing codes and also utilizing a force-balance wind tunnel lest undertaken by CermakPeterka of Fort Collins, Colorado. It was determined that average wind pressures on the building varied between 0.25 kPa (5 psO at the bottom lo 2.9 kPa (58 psf) at the top. Both planar nnd three-dimensional static and dynamic analyses were performed for combinations of gravity and lateral loads. The period of the building was determined to be 5.5 sec.

The lateral load resisting system was initially designed using a purely ailowable strcss criterion. During the optimization effort, members were increased in size, which contributed to increasing the building's internal stiffness. As stiffness was increased, the acceptable limits of building drifl (Hi450) and acceleration (15 mg) were met. In addition, because of the vertical compatibility between ouuigger columns a ld core columns created by the outriggers, analyses were required to determine the gravtty load 'i magnitude in the lateral load resisting system. This nnalysis was performed in steps lo properly model the actual building erection and loading sequences.

Utilization of the optimization program vimmed on estimated 9.8 kgim"2 psf) from the wind-resisting system, a savings of some 15% by weight. More imporlnnt were the savings gained by eliminating cntire components such as two interior bracing lines

j above the twentieth floor, which greatly simplified design and consuuclion.

158 Lateral Load Resisting Systems [Chap. 4 Sect. 4.31 Core and Outrigger Systems 159

17 State Street New York, N. Y., USA

Architect Emery Roth and Sons Structural engineer Desimone. Chaplin and Dobryn Year of completion 1988 Height from street to roof 167.3 m (542 ft 2 in.) Number of stories 44 Number of levels below ground I Building use Office Frame material Steel Typical floor live load 2.5 Wa (50 psO Bnsic wind velocity 17 mlsec (105 mph). 100-yr return Maximum lateral deflection Hl500. 100-yr return Design fundamenlal period 4.7. 5.0 sec Design acceleration 20 mg peak

Design damping I% serviceability Earthquake loading Not applicable

Typc of structure Bundled braced core tubes with perimeter monicnt irame and an outrigger hat truss

Foundation conditions Rock. Footing typc Concrete piers and steel piles Typical floor

Story height 3.66 m (12 it)

Beam span 5.5 to 12.2 m (18 to 40 ft) Beam depth 305 to 530mm (12 to 21 in.) Beam spacing 3.2 m (10 ft 6 in.) max Slab 63-mm (2.5-in.) normal-weight concrete

on 76-mm (3-in.) metal deck

Columns Built-up W350 (W14) core, W610 (W24) perimeter

Spacing 8.53 m (28 ft) core. 5.69 m (18 fi 8 in.) perimeter

Material Steel, grade 250 MPa (36 ksi) Core Braced tubes, grade 250-MPa (36-hi) con-

crete encased through lowest two levels

17 State Street is a 44-story office tower located ncross from Battery Park at the tip of Manhattan (Fig. 4.67). To maximize the unobstructed views of the Statue of Liberty and the New York harbor, the architects chose a quarter-circle floor plan of 1160 m' (12,500 ft') (Fig. 4.68). Although the perimeter of the plan is symmetric, the core of the tower is offset to optimize the arrangement of rental floor space. The first level is 10 m (33 ft) above grade, and typical floors are 3.66 m ( I2 ft) high.


Wind tunnel testing predicted that the wind coming off the harbor would produce loads 40% higher than those required by the New York City building code.

The structural system consists of bundled braced core tubes coupled to perimeter moment frames by means of an outrigger hat truss. The three core tubes are braced with X, diagonal, and inverted V members, as dictilted by core functional requirements. Core


columns consist of W350 (WI1) series rolled shapes in the upper ponion of the building and built-up membcrs below. Pcrimeler moment f m e s have W6lO (W24) series coiumns. rolled and built uo. soaced at 5.7 m (18 h 8 in.). The nerimeter hame; do not a . . ~~~

form a tube, as architectural notches at the comers of the quarter-circle prevent effective economicd transfer of vertical shear forces around the corners. The hat truss is a three-dimensional outrigger two stories high, with diagonals sloping downward from the core to the perimeter.

At the first level. which rises I0 m 133 ft) above the sidewalk the ~erimeler columns and spandrel beam; are encased in cincreie to provide additiooal siffness for the tall story. Below the ground-floor level, the cores are also encased to add stiffness. Footings consist of concrete oiers lo 6-MPa 160-ton/h2) bedrock and end-bearinr steel oiles. Eight columns are Gchorcd for uplif;with postiensioned threadbur rock Gchors.'

Fig. 4.68 Typical floor plnn: 17 SLnle Strcer

162 Lateral Load Resisting Systems IChap. 4 Sect. 4.31 Core and Outrigger Systems 163

Figueroa at Wilshire Los Angeles, California, USA

Architect Albert C. Martin Structural engineer CBM Engineers. Inc. Year of completion 1990 Height from street to roof 218.5 m (717 ft)

Number of stories 53 Number of levels below ground 4 Building use Office Frame material All stccl Typical floor live load 2.5 kPa (50 psO Basic wind velocity 3 1 mlscc (70 mph) Maximum lateral dcflcction 380 mm (15 in.), 100-yr rclurn Design fundamental period 6.5 scc

Design acceleration 17 mg pcnk, 10-yr return Design damping I% scn2iceability; 7% ultimate Earthquake loading Magnitude 8.3 from San Andrcas fault Type of structure Braced corc "spine" with outrigger ductile

frame Found~tion conditions Shnle, 750-kPa (15,000-psn capacity Footing type Spread footings

Typical floor

Story height 3.96 m (13 ft) Beam span 18.3 to 10.7 m (60 to 35 ft) Beam depth 914 to406 mm (36 to 16 in.) Beam spacing 3.05 m (10 it) Slab 133-mm (5.25-in.) lightweight concrete

on SO-mm (?-in.) melal deck

Columns

Size at ground floor 1067 by 1067 mm (42 by 1 2 in.), cruciform shape nl 18.3-m (60-ft) centers

Material Stcei. grade A572.350 MPe (50 ksi) Core Braced steel, grade A572

This 218.5-mm (717-ft)-tall 53-story office torvcr is located in downtown Los Angcles (Fig. 4.69). Tltc floor plan of the tower is 45.7 m ( I50 It) square, exhibiting notches and multiple step backs as it rises above the plaza (F ig 4.701. The square ton8er plan offers internal spacc appropriate to banking and law firms. The granite-clad building has a three-story-tail stepped grccn-colored glass crown, wi~ich is lit from within at night and makes a distinct mark on the Los Angeles skyline. Turo six-story ntriums, botit rectangular in plan, which rise like glass and steel staircases, arc attached to two of the building's corners at 45' angles. Tile plaza of the tower at the corner of Figucron at Wilshire is articulated by fountains and a 12-m (40-it)-high sculplure.

Fig. 4.69 Figucroo nl Wilrhirc, Lor Angels, Cnltiarnio. (Co~rrresy ojCBnf Engiriccrr. Inlc 1


As onnosed to conventional nerimeter ductile tubular frames. the conceot of n saine . . ~~~~, ~~~- ~- ~~r~ ~~ ~~ - r ~ ~ ~ -

structure is used for [his tower. The spine, the unintempled ponion of this lower, consists of a 17.4- by 20.4-mm (57- by 67-h) concentrically braced core linked to perimr- ler columns by aductile frame of outrigger beams. The 'pine in this case has three components (Fig. 4.71):

1. A rectangular concentrically braced core anchored at its extremities by steel columns of a maximum size of 1067 mm (42 in.) square at their base. The interior core bracing and beams are proportioned in such a way that, in case of an in- advertent failure of the diagonals, the vertical load-carrying ability of the floor is not affected.

2. Outrigger beams linking the internnlly braced core to the perimeter columns. These beams not only carry the floor loads, but along with the perimeter columns perform the function of ductile moment resisting frames for the entire structure. The beams are laterally braced to prevent lateral torsional buckling and are con-

$ SYMM.

i

Sect. 4.31 Core and Out?ggwr Systems 165

nected to floor dianhraems bv shem studs lo m s m i t horizontal shew forces to . - . Ihc frame. Nolchcs at the midspan of those beams, which provide for the passage of mcchanlcal ducts, are sllffened lo prevent the formation of a three-hinge mechanism when the ends of beams yield-during a major seismic evenl.

3. The 914- by 762-mm (36- by 30411.) steel perimeter columns which. because of their importance in the overall stability of the frame, nre checked for the loads created by the plastification of all outrigger beams.

Because of the closeness of lateral periods of vibrations with torsional vibration periods. the smciure was checked for the nhennmenon of modal counline. - ~~ - - ~ . -

The spine struclure nor only provided column-frcc uninlcmptcd lease spaces, bul also %as struciurally very efficient. Designed lo remain essenlially elaslic for the maximum credible ea&ou&e. the structure uses I10 kelm' 122.5 ~ s n ~ o f structural steel. as ~~~ - ~ ~ - ~ ~ ~ . . - . . . opposed to aconventional ductile frame, which would have required 132 kglm2(27 psO.

OUTRIGGER

Fig. 1.70 Comporlle flwr plan; Figucroa o l Wilrhire. Fig. 4.71 Spine slruehre; Figuemn st Wllrhire.


Four Allen Center Houston, Texas, USA

Architect Lloyd Jones Brewer Associates S t ~ c t u r a l engineer Ellisor and Tanner, Inc. Year of completion 1984 Height from street to roof 210.5 m (690 ft 8 in.) Number of stories 50 Number of levels below ground 2 Building use Office Fmme material Steel Typical flqor live load 2.5 kPa (50 psf) Basic wind velocity 41 mlsec (92 mph) Maximum lateral deflection H/400,50-yr return Design fundamental period 4.03 sec Earthquake loading Not applicable Type of SINclurl Braced steel core with outriggers to steel

perimeter lramed tube Foundation condilions Deep still clay

.Footing type Continuous mat

Typical floor Story height 3.96 m (13 11) Beam span 12.2 m (40 ft) Beam spacing 4.57 m (15 ft) Beam depth 610 and 915 mm (24 and 36 in.) Material Steel, grade 250 MPa (36 h i ) Slab 82-mm (3.25-in.) light!vcight concrete on

76-mm (3-in.) steel deck

Columns Size at ground level 915 by 280 mm (36 by l l in.) Spacing 4.57 m (15 ft) Material Steel, grade 250 MPa (36 ksi)

Core Braced steel frame, grade 250 hlPa (36 ksi)

The Four Allen Center building rises 50 stories above grade and extends two stories below (Fig. 4.72). The elongated plan, combined with the slenderness of the tower, yields an illusion of exceptional height when viewed from street level. The 133.800 m' (1.44 million it') ollice building is connected to parking and retail facilities by an air-condi- tioned pedestrian tunnel and an overhead pedestrian bridge. Figure 4.73 shows the typical floor freming plan, and Fig. 4.74 illusvales the building section of a typical floor.

The geometry of the slender airloil shape is susceptible lo dynamic oscillation in hurricane-speed winds, thereby establishing a complex and challenging series of structural frame and foundation problems. Wind tunnel tests of an aeroelastic model of the building were recommended and coordinated by the structural engineers. The testing resulted

Fig. 4.72 Four Allen Ccnler, Hourtun, Tcxnr

167


in developing a laternl wind-resisting system to control predicted dynamic oscillation of the building.

A four-celled tube structure was develooed which includes a nerimeter fmmed tube and three vertical trusses m s v e r s e to the eievator core. linked t i the perimeter tube by tree-beam elements. The unique wind-bracing system was subjected to a full-scale test during hurricane Alicia in August 1983, and it performed exceptionally well.

A refinement of the traditional solider pile was developed to retain the 11.3-111 (37- ft-deep foundation excavation. The improved shape reduced the number of piles and

Sect. 4.31 Core and Outrigger Systems

tiebacks nomaily required, thus enhancing economy and shortening the schedule for the basement and foundation construction.

The structural develooment svslem anaivsis. and desisn were facilitated by devel- . . - oping a compmhcnsive series of computer analjses and design progmms. The auto- mated analysis and d e s i ~ n processing ofall elements in the wind-rrsistun~ system of the buiidine sbucture resulted-in sienifiiant savincs in material costs. and enabled the en- - - - u

gineen to complele the design and drawings in a short4-month schedule. Advanced methods were also employed to assure quality control during construe- . . . ~

lion. in pmicular. Ihe project set new slandards of assurance regarding the Gghtness of high-suength bolls. Uilnsonic cxtmsomelers were usrd lo measure bolt lightness accu~ately for the first time on a commercial projecL

The 45.7- by 91.4- by 2.6-m (150- by 300- by 8.5-ft) mat foundation containing 11,127 m3 (13.308 yd" of concrete was poured in just over 19 hours. This was made nossible bv usine a svstem of belt convevors su~olemenlcd by concrete pumps. . - . . .

Thc structural stcel was crccled by fabriculing the exterio;lrcc cuiumns. <he vertical core trusses, and the uce beams in modules to reduce [he number of pieces lo handle and fieid connections to comdete. The ail-steel smcture was erected at a rate of one corn- plele noor every 2 % day;. n t e project was completc 6 months ahead ofihe planned fast- track design and construction completion date, with the first lcnanl mo\'ed in jusl 15 months afler construction of the foundation began.

The project received the following awards:

Q!!J I ! I ! ! . ED -

I.. I%_

" "'3"B-

Fig. 4.73 Typical noor framing plnn; Four Allen Center.

. "One of the Ten Outstnnding Engineering Achievements in the United States of America," National Society of Professional Engineers, 1983

'

"Grand Award Winner for High Professional Execution of Engineering Design," American Consulling Engineers' Council. 1984 "Eminent Conceptor Award for the Most Outslanding Engineering Project" Consult- ing Engineers' Council of Texas. 1984

Fp. 4.74 Enlnrgcd building reelion-lypicnl noor; Four Allen Center.


Trump Tower New York, New Vork, USA


Year of completion

Height irom sLreel to rooi Number of stories

Number of le\'els below ground Building use Framc material Typical noor live load

Basic wind \,elocity


Design fundamenVal period Design accelcretion

Dcsien damping Eanltqunkc loading

Type of structure

Foundalion conditions

Footing type

Typical floor

Story height Slab

Columns Size at ground floor

Spacing hlatcrial

Core

[Chap. 4 I Sect 4.31 Core and Outrigger Systems

Swnnke Hayden Connell

Oftice of Irwin G. Cantor

1982 1 0 1 m (664 It)

58 3 Retail, offices, residential

Concrclc 5 kPa (100 p ro rerail: 2.5 kPa (50 psi) of- liccs; 2 kPa (4D 11~1) rcsidcnti:~l

Unavailable: iorcc = 1.0. 1.25. 1.5 kPa (20.25.30 psi) Hl600. 100-yr return 5.2 sec 16.5 mS peak. 10-yr rcturll

i.5%

Not applicable Concrctcshcarcoie linkcd by cuncrelcout- rigger walls lo conarcle pcriltielcr rralncs

hlonhattan mica schist Sprcnd footings

4.8.3.66.2.9m(lh,12.9.5111 400-mm (16-in.) waffle slab: 190-nlnl (7.5-in.) flat slab

813 by 513 rnm(32 by 37in.)

12.2 to 7.3 m (40 lo 24 it)

Concrete. 49 MPa (7000 psi) Shear walls, -157 mm ( I 8 in.) thick at ground floor in 49-MPa (7000-psi) concrctc

Trump Tower is n multiuse building occupying a prime site on 5th Avenuc in New York City. T h i o u ~ h the purchase of the air rights for adjacent sites and irom bonuses awarded for the provision of public atncnities, a plot ratio (building floor arcJ lo site area) o f21 was achieved, making this a very slender building.

A perimeter tube lateral load resisting sysleln was unacceptable due to the impact o i closely spaced columns on the views from the condominiums and on t l~c shop fronts at street level. Also, structural steel was rejecled due lo the lead lime required Tor supply to the site. The adopted all-concrete solution u!ilized concrcte shear !\,ails for l;~leral load resistance and deep concrete lransier girderr to chon%c the structural column grid (Fig. 4.75).

Column and rnll lond and lnlcrnl dirplnccmcnt; Trump To~ucr, New Ynrk.


Through the 38 condominium levcls, loads are carried by 52 concrete columns and concrete u d i s around the service corc. At moflcvei, twin oulrigger beams 6 m (20 11) high and 450 mm (18 in.) thick link the corc with perimeter columns on two opposite sides to reduce latekdisolaczment. Extended core walls do this iob in the other direelion ~ - - ~ -

Below the twentieth floor a system of lransler girders 7.3 m (24 it) high and 450 to 600 mm ( I 8 to 24 in.) thick allows for the 52 columns to reduce to only 8 columns through the 13 office levels. The transfer girders nlso act as outrigger beams to further control lateral displacement. The girders are pierced by many openings for doors, pipes, and ducls.

Another transfer system comprising an inclined-column A frame was introduced between the eleventh and seventh noon lo allow mother two columns to be removed in order to open up the atrium, which rises seven levels through the retail floors at the base of the buildine. -

The 1087-m' (I 1.700-it2) rcsidcntial floors wcrr poured on a ?-day c)cle. n ~ c 56- and 49-hlPa (8000- and 7000-psi) concrete for the columns contained a superplasticizer to increase workabilitv for vlacine around dense reinforcement. Tieht manGement of . . - - - concrete delieerics uas requ~rcd to ensirre that high-strength concrete %,as avsilablc at the right time for placement in s l ~ b s over and around columns.


Waterfront Place Brfsbane, Australia

? ; . 5 ' @ @; Architect

... , Cnmeron Chisholm and Nicol (Qld.) Pty. Ltd.

Stmctuml engineer Bornhorst and Wnnl Pty. Ltd. Year of completion 1990

Height from street to roof 158 m (518 ft) Number of stones 40


Frame material Concrete Typical noor live load 3 Wa (60 psfJ Basic wind velocity 49 mlsec (110 mph) Maximum lateral deflection 185 mm (7.25 in.), 50-yr return Design fundamental period 5 see Design acceleration 2.3 mg (standard deviation), 5-yr return Design damping I% serviceability; 5% ultimate Earthquake loading Not applicable

Typc of structure Shear core with outriggers to perimeter columns

Foundation conditions 17 m (56 ft) of soft clay over rock Footing type 25-m (82-it)-long 1.5-m (5-it)-diameter

bored piles socketed and belled in rock Typical noor

story height 3.6 i (12 it) Beam span 11.5 m (38 ft) Beam depth 420 mm (16.5 in.) Beam spacing 6.8 m (22 ft 4 in.) Material Posttensioned concrete Slab 130-mm (5-in.) reinforced concrete

Columns Size at ground floor 1350 mm (53 in.) in diameter Spacing 6.8 m (22 ft 4 in.) Material Concrete. MI to 35 MPa (8600 to 5000 psi)

Core Concrete shear walls Thickness at ground floor 600 mm (24 in.) max Material Concrete. 45 to 35 MPa (6-100 to 5000 psi)

Waterfront Place is a 42-level reinforced concrete framed office tower, located at tile rivcr edke of Brisbane's central business district on a 15,000-m' (160,000-flZ) site (Fig. 4.76). A steel-level plaza provides access to the river edge for the public, whereas bclow and abow river level there is parking for 500 cars. River cdge boardwalks connect

174 Lateral Load Resisting Systems [Chap. 4 S e c t 4.31 Core and Outrigger Systems 175

Fig. 4.76 Wnlcrlront Place, Brirbone, Auztrolln.

ncifhboring developmenis with thl: p1311. ilnd mooring is pro!,ldedon the a;1ierfroot for plc~surr.craft, tour boats, and ferries.

The 42-level tower provides 36 office floors, three plant-room floors, a ground-floor foyer, and two basements. The configuration of a typical floor provides 12 m (40 ft) of column-free space between core and glass line, with four cantilevered bay windows on both the east and west facades, effeclively contributing 10 "corner" windows on each floor (Fig. 4.77).

High-rise buildings taller than approximately 35 stories may not be structurally cco- nomical if the core alone is used to resist wind loads. This is particularly thc case for a building rectangular in plan loaded about its weak axis. Such was the case with Water- front Place, which has 40 levels above plaza level.

Wind tunnel model testing was undertaken, and the results indicated that it would be impractical to use the core to fully withstand wind forces. Wall thicknesses and reinforcement quantities would be excessive, as would be the sway of the building in the east-west direction.

Instead the design concept was changed to that of a core-perimeter interaction structural system where the core "tube" is connected to the exterior columns at specific locn- tions, in this case at the plant room at levels 26 and 27 (Fig. 4.78). At these levels, four stilC"wind beams" cantilevering from the core are connected to perimeter transfer beams between three columns on each lace ofthe building. This induces participation ofthe axial capacity of the exterior columns in resisting wind-induced loading (Fig. 4.79).

The core is used to resist all horizontal shear, but vertical shear resistance is transferred from the core to the exterior columns, thereby utilizing the total overturning capacity of the SINClUre.

I 3 . Y__I

Fig. 4.77 Typieul rnidrire noor plon; WnlcrCront Plorc.

I


CORE WALLS

WIND BEAMS

COLUMN LOAD

SPECIAL JOINT

TOWER AND PLAZA . - _ _ * . - - A . E A S T WEST SECTION

Fig. 4.78 Tower nnd plnm wt-wstserlian: Waterfront Place.


Research indicated that the most effective location for the wind beams was at the top levels of the tower. However, this was impractical due lo the stepped profile of the top- most three plant levels (levels 37, 38, and 39) and the marketing potential of tenancy levels 29 to 36. As a consequence the wind beams were placed at levels 26 and 27. two '. . floors containine mechanical rooms and of ice space.

This loca~ion~hri~htcned the possibility of diifcrentiai axial shoncning between the reinforced concrele core and the colu~nns. A ,lee1 joint was developed to link thc out- rieeer beams with the fransfer beams at the columns lo allow controlled slippage as Lhe -- .. - dilfcreniial movement occurred.

Thc use of the cantiicvcring wind beam syslem introduced some architeclural and siructural cncinecrine dcsirn challenecs. In order to rcrist the 820-tonne (180.000-lbl - - l o ~ d appiied;o thc end ofcach wind hiam. the h e m s had lo be tuo stories high and 900 mm (36 in.) thick and prefenbly without any penetrationr. To have no pcncvations would have meant the ldss of o f f i e soace: th&efore laree ooenines were made in these - . - beams. This precluded the use of conventional beam design theory for these beams. Consequently the beams were desipned using "strut and tie" theory. Concrete of 55- MPn ff800-osil streneth and ties cinsistine i f 45 36-mm f 1.4-in.1-diamcler bars were required to ;ra;mit &! working load of 86 tonnes (1 80,000 lb) per beam.

The noor slabs at levels 26 and 28. which are locally 420 mm (16.5 in.) thick. par- ticipate in the wind-beam action by working as flanges for the wind beams. The force paths in the wind beams and the floor slabs arc shown in Figs. 4.79.4.80, and 4.81.

Differential venical shrinkaee betureen core and ~erimetcr columns at level 26 sub- sequent to construction of the entire building was caiculated. Consvuclion history, material propenies, and in-service loads were used in this calculation.

+L-LrL

FIG. 4.79 Level 26 noor plun-r,,reer trnnrmlttcd througtl nnorLanungc"; Wnlcrrronl Plncc.


Fig. 4.80 Str~Ulie tmrr-rt~rce up; \Vulcrrronl Ploec.

Fig. 4.81 SlruUtic truss-rorec dcmn: Il'ulurlronl t'larc.


The wind beams are extremely stiff. Design load deflection was calculated to be only 2 mm (0.08 in.). Unless some means of allowing movement between wind beam and columns was found, the wind beams would have attempted to support the 15 stories above level 26 and several stories below. This it could not do, and swc tun l failure would have resulted. A sliding friction joint between wind beams and the column transfer beams was developed. This is shown in Fig. 4.82. The joint is in effect a multiple clutch with the slip load determined by the clamping force provided by the through bolts.

Tests were canied out at the Queensland University of Technology to determine the co-efficient of friction between the brake-pad material and the stainless-steel plates. Size, clamping force. and loading rate effects were investigated. Typical load-slip graphs are shown in Fig. 4.83. Eoch joint is fitted with four strain gauges to monitor stresses in the plates and hence the load being transferred through thePclutch." This allows the clamping force to be adjusted to slip at the required design load. When the clamping force is finally adjusted, it will not require any fudher adjustment in its life. A typicnl plot ofstress versus time for one of the joints is shown in Fig. 4.84.


Section 9

Elevation on slip joint

Plan detail of slip ioint

rig. 4.82 Slip joint; \\'alcrfmnt Plituc.

! Sect. 4.31 Core and Outrigger Systems I81 I 75% of maximum

Slip (mm)

Slip (rnrn)

Fig. 1.83 Friction ! e r e Wolerfrunt Place.

T I M E ( W E E K S 1

Fig. 4.81 Typicnl rlruin-gouge rcudingr on vind-beam juinl: \!'nlerfrunl Pincc.

Lateral Load Resisting Systems [Chap.

Two Prudential Plaza Chicago, Illinois, USA

Architect Loebe Schlossman and Hackl Structural engineer CBM Engineers. Inc. Year of completion 1990 Height from street to roof 278 m (912 ft) Number of stories 64 Number of levels below ground 5 Building use Office Frame material




Design ncceleration Design damping

Eanhquake loading Type of structure


Footing type

Typical floor

Concrete to level 59, steel above 4 kPa (80 psf)

31 d s c c (70 mph)

488 and 419 mm (19.2 and 16.5 in.). 50-yl return

7.2.5.8. 4.4 sec

19 mg peak. IO-yr return 2% serviceability Not applicable

Shear core with outrigger beams and perimeter frame

14-m (45-ft) fill over 11-m (35-ft) hardpan over rock

15-m (50-ft) hardpan caissons and 24-m (80-fl) rock caissons

Story height 3.96 m (13 ft) Beam span 12.2 m (40 ft) Beam depth 610 mm (24 in.) Beam spacing 6.1 m (20 ft) Slab One-way 150-mm (6-in.) slabs, typically

28-MPa (4000-psi) concrete Columns

Size at ground noor

. ~

Material Core

890 by 1140 mm (35 by 45 in.) at 6.1-m (20-ft) centers

Concrete, 84 MPa (12.000 psi) . ~

Shear walls 840,610. 460 mm (33. 24. 18 in.) thick at ground floor

Material Concrete, 84 MPa 112.nnn ,,;r . ,--- r-., Two Prudential Plaza, a 64-story office building, is located in downtown Chicago, Illi- n01"Fig. 4.85). At the time of completion it was the second tallest concrete building in the world. The building has a gross area of about 130.000 m' (1.4 million ft'). It has five levels of basement, which are primarily used as a parking garage for 325 cars. The low-

Fig. 4.85 Tno Prudcnlinl Plaza. Clxicngu. Illinois. ICoirnen ojCBAl E , r ~ t n ~ . ~ r r i,,c )


cst bxcment is locatrd nt elev3lion -6.477 m (-21 fi 3 in.) CCD (Chicago Cily dntom). The lobb) ofthe building is locatrd at elevation T 10.668 m ( 7 3 5 ft 0 in.) CCD. Lev- els 4.5.38, nnd 39 are used for mecltmical equipment, and level59 for siorace of u in- dow-washing equipment Level 58 is the last office floor. Levels above 59 are mcchnn- ical floors.

The building is rectannular at lhe lower levels. 37.4 bv 40.4 m (122 ft 6 in. bv 132 ft - - . 8 in.), but becomes square at the fifty-ninth floor due lo a series of rcrb3ck on the nonh :and south faces. Above lhr. fifty-ninth floor. lhr building sti\nq tapering to form a "cone held." which is torrrred bv a 25-m (82-11) architectural soirc. The 10" rlcvniion of the spire is 304.8 m ( i i00 f t j c c ~ ( ~ i g . 1.86).

The lateral stiffness in each direction is mainly provided by the four shear walls located in lhe core of the buildine. Their deoth is 13.8 m (45 f t 4 in.). The flanees are 838 rnm (33 in.) thick a d the wzb; are 610 a id 380 mm ( i 4 and 15 /n.) thick Tor the inte- nor and extcrinr ualls. rcspeclively. The south shear wall drops off nt level 27 where&$ the nonlt w11l drorrs off at leiel 40. Tile middle ualls conlinue 111 !he wav lo floor 59. The flanges of wails arc connected together in the north-south direction by k86-mm (27- in.)-deep link beams.

The columns at the east and west faces are soaced at 6.1-m (20-ft) centers. whereas . . . ~

on the north and south laces they arc spaced at 9.15 m (30 11). The typical extrnor column sire vJries from 8'10 by 1140 mnl (35 hy 35 in.) at the lo\ver floors to 600 h\ 600 mm (24 bv 24 in.) e the ton floor;. A maximum concrete streneth of 84 MPe 11$.000 - . - psi) u'as used for columns and shear walls at the lower floors. The concrete strength was reduced to 42 MPa (6000 psi) at the upper floors.

The floor beams have a clear snan 3 aooroximarelv I2 m (40 ft) from the oerimetcr . . . . columns to the shear r\,311 cure. Typical floor bcam size is 965 mm (38 in.) by 610 lrlm (24 in.) deep. Floor framing consists of a 150-mm (6-in)-thick norrn>l-weight concrelc sllb u,ith o clear span of 5 13 in (16 f l I0 in.) be1ncr.n rhc noor beams. spaced st 6 I m (20 ft) centcr5. In addillon tu carrying the gmvity load. rbe floor beams carry some 01 the wind shear frum the shear ivalls to the outside columns. At the fortieth and 111c filly- nineth floors the core is tied to the outside columns at two locations with the helo of oil- , rigger ivnlls to control the wnd drift and reduce Ihe overturning monlent in thu core shear walls The beams are 5.03 m (16 f16 in.) deep (in other words. a full nory high) butwcci~ floors 39 and 10 ind 1.68 m (5 11 5 in.) deep ar floor 59. . .

The foundation system consists of straight shaft caissons up to 3 m (10 ft) in diameter. These caissons rest on the bedrock, which is about 30 m (100 fr) below the existing ground level. The allowable bearing capacity of this rock is 19 MPa (200 tonlft'). To fully utilize this capacity, 56-MPa (8000-psi) concrete was used in caissons. In the park- inggange adjacent to the main tower, belled caissons were used. These caissons extend to hardpan about 21 m (70 ft) below existing grade. The allowable bearing capacity for this hardpan is about 3.4 MPa (36 todft').


+1!22'-6''+

-. : % C X m: at LON \

Fig. 4.86 Typlcnl floor plnru: Two Prudenlinl Plnm.


7999 Broadway Denver, Colorado, USA

Architect


Height from street to roof Number of stories Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity

Maximum lateral dctlcction Earthquake loading Type of structure

Footing type Typicnl floor


Beam depth

Beam spacing

Slab

Columns Size at ground level Spacing

Core

Material

C.W. Fentrcss and Associates P.C. Sevemd Associates 1985

198 m (650 it) 43 3

Office

Concrete corc, srcel frame 2.5 W a (50 psi) 36 mlsec (80 mph)

HI400 USA zone 1

Concrete corc with outriggers to perimeter stccl fmme Caissons

3.81 m ( I2 ft 6 in.)

9.14m (30 it)

406 mm (16 in.) 3.43 m (I l ft 3 in.)

83-mm (3.25-in.) lightweight concrete on 50-mm (2411.) metal deck

W350 by 1088 kglm (W14 by 730)

4.57 m (15 ft) Shear walls 610 mm (24 in.) thick at ground floor Concrete, 42 to 28 MPa (6000 to 4000 psi)

1999 Broadway is an unusual 43-story office building built on a triangular site. The presence of an historic church on pan of the site resulted in the plan of the office building having the shape of an arrowhead which wraps around the church, creating from it a piece of sculpture on the plaza (Fig. 4.87).

The facade comprises alternating bands of limestone and green reflective glass and a concave cunain wall having seven angled facets around and above the church. The building has been raised 15 m (50 ft) above ground on 22 limestone-clad columns to create views ofthe church from within.

The slroclurc cunsists of^ rr.inforccd concrde curvicc core. stccl perimeter columns. and stcci flnor b s m s and g~rdcrs co~nposile with tile rlah. At Ic\r.lr 3 10 5 and 29 lo 31. two-story-high outrigger trusses between core and perimeter columns reduce thc lateral deflection. Girders are connected to plates field-welded to cast-in plates in the slip-

S e c t 4.31 Core and Outrigger Systems .-. formed core. The perimeter frames act with the core to resist lateral loads and effects due to the eccentric form of the building.

Footings comprise cast-in-place caissons founded in claystone and sandstone some I5 m (50 ft) below grade. A single caisson supports each column, and caissons at a minimum spacing of three caisson diametem are distributed around the core. The design end bearing pressure was 3350 kPa (70,000 psO, and skin friction in the rock was 335 W a (7000 psf).

Fig. 4.87 Typicnl noor plnn; 1999 Broadway, Denver, Colorado.


Citibank Plaza Hong Kong

Architect Rocco Design Partners

Structural engineer Ove Amp and Partners

Year of completion 1992 Height from street to roof 220 m (722 it)


Building use Office

Frame material Reinforced and posttensioned concrete

Typical floor live load 5 kPa (104 psO

Basic wind velocity 64 mlsec (144 mph). 50-yr return, 3-scc gust

Maximum laleral deflection 370 mm (14.5 in.). for50-yrrcturn period wind

Eanhquake loading Not applicable Type of structure Concrete core with outriggers

Foundation conditions Dccomposed granite over granite bedrock Footing type Hand-dug caissons to rock Typical floor

Story heighr 3.9 m (12.8 it) Beam span 9.4 m (31 ft) Beam depth 500-mm (20-in.)-deep ribbed slab Beam spacing Reinforced concrete ribbed slab

Columns Size at ground floor 3000 by 1900 mm (120 by 75 in.) mnr Spacing 9.4 rn (3 1 ft) Material Concrete with 40-MPa (5800-psi) cube

strength Core Shear walls 1.0 and I.?, m (3.3 and 4 it)

thick at base Material Concrete with 1 0 MPa (5800-psi) cube

strength

The four-level basement of Citibank Plma (Fig. 4.88) was formed using top-down construction techniques. Stability \vas achieved with the internal cores acting in combination with the perimeter columns, using outriggers at two levels (Fig. 4.89). Part o f the building is seated above a major entryway to a neighboring development. To achieve this, the perimeter columns rake outrvnrd along one face of the building over a one-story height (Fig. 4.90). The resulting lateral forces were resistcd by a prestressed beam system tied back to the internal cores. prestressing being applied in stages as construction progressed.


hg. 4.88 Cllibank Plnzo. Hung Kong. (Cac,ncrr o f o l e A n q orxdporinrrr]

190 Lateral Load Resisting Systems Sect. 4.31 Core and Outrigger Systems 191

7B.&

Fig. 4.89 Fioorplnn; Citibnnk Plnrs.

Pig. 4.90 Section through mking columns; Cilibnnk Plorn.


4.4 TUBULAR SYSTEMS

7 Historical Perspective

The development of the initial generation o f tubular systems for tall buildings can be t r n r ~ d to the concurrent evolution o f reinforced concrete construction followine World ...... .- ~~~~ ~ - War 11. Prior to the early 1960s. reinforced concrete was utilized primarily for low-rise construction of only a few stories in height. Ti~esr bui ldin~s were chancterized by planar Viercndeel beak and column arraneemcnts with wid;soacines between membcrs. . - The basic ~ncfficieacy of the frame wcleln for rsioforc:d concrete buildings or more t1r~11 ahnut I5 slnrlcs rusulttd in m:,ober proportinns or prohthit~te .ire and rlruclur;~l material cost or~miums. and thus such svitcms were economicallv inviable. Concrete shear ual l systems arr;lnged i \ ~ t b i ~ t 111s huilding int~.riur c o ~ l d be utilirud. b.11 lhcy uerr. oftc~t of insul'licicnt sire for aliifne,~ and rcsil;,ncs ;lgain%t orcrturnlng. Thi, Icd tu lhr. dcvclonment ofstructur~l svstems with a hirhcrdcrrcc orcfficicncv toward lateral load - - rci\t.lncs lor 1311~.r h~ildings. The nntlon n i i fully thr~u~dimcn~ionaI i ruclur;~l sjrlum uti l iz~nc th~. cnlir~. build:nc inertin lo rcrirl l s l ~ . r ~ i loads b:wn lo cmcrec ;I[ lhls time. Thc main orooonent o f thi;desien trcnd was Fszlur Khan. who svstem~icallv oursucd ~ ~ , , - , . a logical evolution of tali building structural systems. The pervssivc international-style approach 10 archilecture a1 the lime included lergcr open spaces with longer spans, a well-oraanized core. and a clcarlv ocrceotiblc interior-exterior column grid. Wilhin this , . . ;~rui~iteclur:tl 2nd ecnnnmic clinl:!lc. Ihc fr-1111cd Iuhi. h).\tcin in rd IIIOICL.~ c~lncrct: i : t l l

hi. \c:n ;lr bull) ;I n;~ttlr-l 2nJ 3,) innur:.l!\u ~:~~IO~IIISIII in tidl b.tilcling <yhtL.nl,

2 The Framed Tube

The orcnniration ofthe framed tubc svstcm is acncrallv one ofciosclv soaccd exterior - - < .

columns and deep spandrel bcama rigidly connected together. with the enlire assem- blaee continuous aionr each facade and around the building corners. The system is a loekal cxansion o f the moment resirline frame. whcrebv the beam and coiumn s t i r - - ussses are 1 1 1 c r r 3 ~ d dram;!ric:ill! hg ruducirlg ltle clear sp;tn dirnensionr and incrr3stng thl: rnclnbcr d c ~ ~ l t s . Thd monoiilllic oaturr. u f rcinfurccd corlcrcte runrlructinn is ide311y suited for sucha svstem. in\,olvinr fully continuous interconnections of the frame mem- - . bers. Depending on the heighl and dimensions of the building, exterior column spacings should be on the order o f 1.5 to 4.5 m (4.9 lo 14.8 ft) on center maximum. Spandrel beam de~ths for normal office or residentinl occupancy applications are t v~ ica l l v 600 to 1200 m k 124 to 47 in.). The resuitine arranremcnt ao~r~x imates a tub; cantilcvcrcd

svsiem costs. Exterior columns mav eliminate the need for intermediate vcrtical mullion elcntunls of ti>c uur1;lin \$:dl 133~11311) ur 1.)1311g. A iIrUClUr.lli51 ?Xpr~:isinn fur tile e \ l ~ - ridr envelope msy hc lull? rc;~l iz~.J b! <\pnslng IIIC ~.xldrinr tuhul;,r mernb~.~;, IIIUS dclinong >he xil1,>r.~!-r31 Jen~.str:,li~~~>. TI,< ~L i l l dn !~ ! L i l l l i).st?rn 15 1hc.n infilled i,etre~.n the coi&~ and spandrel beams. with II resultino reduction in claddine cost. An eariv ex- ampie o f such a iubuiar b u i l d i n in rcinforccd~oncrete is shown in Fig. 4.91.

*

The behavior ofrrarnrd tubes under Interel load is indicated in Fig. 4.92, which shows the distribution o f axial forces in the exterior columns. The more the distribution is similar to that o f a fully rigid box cantilevered at the base, the more efficient the system wi l l be. For the case o f a solid-\$,all tube. [he distribution of axial forces would be expected to bc uniform over the windn.nrd and Iccivard \tSslls and linear over the sidcrvnlls. As the tubular walls are punched, creating the beam-column frame, shear frame deformations

Sect 4.41 Tubular Systems 193

Fig. 4.91 Brunrwiek Building, Cl~icugo. lllinoir.

~ d ~ r r a ~ ~ o a o nes~sr~ng hysrems [Chap. 4

ore introduced duc lo sltear;lnd flcxurc in the tubular mumbcrs as uu l l as routtons 01 thc ntcmber loin&. This rcdtlccs the eilecti\e stlffnrss Of lbe systeln as a cantilever. The extent to which h e actual axial load distribution i n the tube columns dcoartr; from the idesl ~. - ~. ~

is rcnndd the ",hear lag effect." I n behavioral terms. the forces in the colurnns toaard lltu lniddls u i the flange frnmus lq behind those nearer the conter and are tltua less than fully ulllized. Limiting the shear lag ellect is essential fnr oplimal de\.elopmen~ o f the :ubulnr system. A rc3son;1blr. objcctit,e is l o strivc toward a1 least 7% effiricncy sucll [hat the cantilever component in llte oterall rystcln deflection ondsr u ind load dnminatus.

Thc 1r;tmed tubu in structural slsel rsquirus wcldinp oftlte heam-column join1 tu du- !clop rigidity and continuily. Tllc ~onn3t ionof fahric~tcd 1rr.u elemenlr, rrltcre all welding is p:rformcd i n llte shop i n a horizonwl position, has made the alrsl-frame tuhe s ~ $ . tem more practical and efficienl, as shown i n Fie. 4.93. The trees are then erected-bv ~, bolting the ipandrcl bcotn* togelher ak Inidspan near thc pnint o f innrxion.

The column spacing in steel-fmntrd tubular buildings lnust be ~.ralualcd to b~l;tnce llte nerds for higher cantilever dfiicicauy throuph clorcr anactnkr rvitll increased F ~ h r i - cation costs. The use ordeeper, built-up sectioni versus roiled Gmbcrs is also a matter o f cost-effectiveness. A survey o f steel quantities for completed tubular buildings is s l~own in Fig. 4.94. The buildings range from 40 to 110 stories. and column spacings generally range from 3 to 4.5 m (10 to 15 ft) on center, with spacings as close as I m (3.28 ft) i n the case of the 110-slory World Tradc Center twin towers. New York (fig. 4.95). These towers are examples whereby the structuralist notion o f a punched wall tube with extremely close exterior columns is architeclurally exploited to express visu- ally the inherent venicality o f the high-rise building.

Elevation

Cantilever componenl

I Shear frame component

I Sway

Dlslribullon w l h w shear lag

Actual axial stress

shear lag

Wind lorce t Fg. 4.92 Frulncd tulle i~clv~rior.


Fig. 4.93 Typical tree crcction uniL

HEIGHT (in) Vlg. 4.94 Conlilcv~r systems, stccl qunntity versus hciglxt


3 The Trussed Tube

,\, ihc tubular concept; were being dcreloprd in ihr 19605, il became Jppdrent that thcrr was a cenain building height n n g e for which the framed tube could be elficlenll) adaoled. For rrry 1311 buildings. lhe dense grid of beam and column members has a d t - =id;d impact onihe facade aGhitecture. The need lo control shear lag and improve the

I 9 \Ysrld Trndc Center, New Ynk. lCo,mrry rfLrrlii. Robcrrrnr, n ~ i ~ l . i r m r 1

Tubular Systems

systemefficiency can only be realized by relatively small perforations in the tubular walls. The problem becomes particularly acute at the base of the building, where archi-

1 @$ teclural plannine lypically demands open access to the bulldine interio; from ihe sur- . I . , rounding infrastruaurd will1 as lilrlc encumhr;mre 2s possible {om the sxlerior fr;~me- k.; n,orI;. A number ofulcgant solutians inrolving Ole transfer and rcmovnl oftlle e~turi,,r

columns at the base of the building have been iomulated (Figs. 4.91.4.95, and 4.96). '".~~t~pcharnc~eristically include an associated material premium.

The trussed tube system represents a classic solution for a tube uniquely suited to thc qualities and chmc le r of structural steel. The ideal tubularsyslem is one which intercon-


~. , .

[Chap. 4

The bundled tubc concept allows for wider column spacings in the lubulu walls lhan w o ~ ~ i d br oossible with unlv lhc eatrrior framed lube form. 11 is his sp3cine uhicll rnnkes it possible to place inierior frame lines withoul setiousiy c ~ m ~ r o ~ i s i n g ~ i n l e r i o r space planning. In principle, any closed-form shapemay be used to create the bundled form (see Fig. 4.102). The ability to modulate the cells vertically can create a powerful .,2

vocabulary for a variety of dynnmic shapes. The bundled lube principle therefore offers , *.?;s.::!:s great latitude in the architecturnl plnnning of a very la11 building.

t t t t t t t

Sect. 4.41 Tubular Systems

114 P L A N S

TYPE

SIZE

H I W

0c0101

ENDCHANNEL TRUSSEDTUQE

MOMENT RESISTING FRAME OR FRAMED TUBE

Fig. 4.99 Pnrtiul Lubulnr ryslcrn.

-COLUMN AXIAL DUE TO WIND

::: s 0 0 ..

LOADS

CASE (A1

EXT. TUBE EXT. TUBE EXT. TUBE BUNOLEO TUBE

6 9 m x 6 9 m 46m r 4 8 m 23m x 23m 69m x 69m

6.65 9.60 19.00 6.65

0.61 0.75 0.66 0.78

Fig. 4.98 Trurrcd tubc, grurity loud rrdlrlribstion. Fig. 4.100 Sludy of tul~ulor cllicicnry.


r COMPRESSIVE STRESS

MASTER GRID STRESS OF COLUMNS

AT BASE

(a1 FRAIAING PLAN Ibl SHEAR LAG BEHAVIOR

1:ig. 4.101 Uundlrd tube bchuriur: Sears Tower, Clnicugn, lilineir.

Sect. 4.41 Tubular Systems ,03 1

PROJECT DESCR~PT~ONS, FRAMED TUBES

Amoco Building Chicago, Nlinois, USA

Architect Edward Durrell Stone with The Perkins

l and Will Partnership

Swctural engineer The Perkins and Will Partnership I Yenr of completion 1973

342 m (1123 A) Height from street to roof Number of stories 82. Number of levels below ground 5 Building use Office

Frnme material Structural steel

Typical floor live load 4 Wa (80 psO Basic wind velocity 1.4 X Chicago code Design wind load deflection HI400 Earthquake loading Not applicable

Type of svucture Perimeter fnmcd tube Foundation conditions Silty clay, sand, and gravel over massive

dolomitic limestone Footing type Concrete caissons. 1.5 to 3.8 m (5 fl to 10

ft 3 in.) in diameter. approximarely 24 m (79 ft) long

Typical floor


Truss span 13.7 m (45 fr)

Truss depth 965 mm (38 in.)

Truss spacing 3.05 m (10 ft) Material Swctural steel Slab 140-mm (5.5-in.) lightweight concrete

slab; 35 MPa (5000 psi) on 38-mm (1.5- in.) steel deck

Columns Folded plate, size not available

Spacing 3.05 m (10 ft) center lo center

Material Stcel, grade 250 MPa (36 ksi)

Core Structural steel frames carrying gravity loads only

Fig. 4.102 hlndular tuher.

/ ,!j The innovative structural concept applied to this 342-m (1 123-ft)-high building resulted , from the desire to achieve an efficient, simple to erect structure utilizing a perimeter i tube whose behavior would closelv anoroximate that o i a oure cantilever (Fie. 4.103). I . . . . -

The lubc compriaca uolulnns uf V-rhaped kcel plaw 3nd du:p ubxnnul.shapud bcnl- plat: spandrel bcams shop-fabncalcd Inlo 3-stor) Irccs. Tb:r< arc 64 sucll columns ;,t 3- I


m (10-11) centers around the perimeter, plus solid steel plate walls to the reentrant corners. The free inner edges of the columns are stiffened by heavy angle sections. Connec- tions between spandrel beams comprise simple high-strength bolted joinL5, whereas column splices are welded at lower stories and bolted or welded at upper stories.

The floors are generally supported by 13.7-111 (45-11)-span trusses at 3-m ( 10-ft) centers. Trusses at successive floors attach to alternate sides of a column to effectively cre- ' .

Fig. 4.103 Amoco Uutldtng, Chtcugo, lllinuis. (Pl>nin h? Jrrr BairB.)

f&' Sect. 4.41 Tubular Systems 205

i i . ::

:: ate a concentric load in the vlane of the wall. At the buildine corners the shorter-soan diagonal girder and attached'beams are wide-flange sections. ?he 4000 essentially identical lrusses and the comer beams were mass-produced in an assembly line.

Economv was achieved bv creatine a ~e r ime lc r frame irom thin steel olate .;oread - . . -. !,.,.i,over as much of the facade as was architecturally acceptable and by maximizing the ;?:?'number of geometrically identical elements. The arraneement also negated the need for

sublramine for the exterior curtain wall. -

- The space within the V-shaped columns was used Tor air s h a h and hot and chilled

water pipes for the perimeter zone. The interior zones were s u e ~ l i e d from vertical shafts in the bore

The building contains45.900 lonnes (50.506 tons) ofsteel,ofwhich 37% is in beams and trusses and 63% in columns and reentrant corner wnlls.The r\reieht ofsteel amounts

Sect. 4 41

181 West Madison Street Chicago, Illinois, USA

Archilcct

Structural engineer

Year of completion Height from streel to roof

Number of stories Number of levels below ground Building use Frame malcrial

Typical floor live load Bnsic wind selocily Maximum lateral deflection

Design fundemenla1 pcriod

Design acceleration Design damping

Earthquake loading Type of slructure

Foundation condiiions Footing type

Typical floor

Story height

Benm span

Benm spacing Benm depth

Slab

Columns Spacing blalcrial

Core

Thickness a1 ground floor

The I 81 West Madison Sbcet lowe Wells Streets in [he Chicago Loog backs and a distinctive cro\r8n that 1920s. This is also n tower for the with n center square concrelc core

Cesar Pelli and Associates with Shaw and Associates

Cohen-Barreto-Mareherlas Inc. 1990

207 m (680 ft) 50 1

o m c e Concrete corc, steel perimeter frame 2.5 kPa (50 psf) -13 mlsec (97 mph). IOO-yr rclum period

400 mm (16 in.). IOO-yr return period

8.3. 6.7 see horizontal: 6.3 sec lorsion 18.4 mg peak

I .5% senaiceability

Not applicable Concrete core lube with stccl perimeter tuhc

Hardpan. 1.7-MPa ( 2 0 . ~ ~ 0 capacity Caissons. 24 m (80 ft) long. 1370 mm (4 fl 6 in.) in diameter, belled to 3-m (IO-ft) diameter

3.96 m (13 ft) 10.36 m (34 ft)

3.05 m (10 fr)

530 mm (21 in.)

140-mm (5.5-in.) composite metal deck W350 by 745 kglm (14 in. by 500 Iblft)

6.1 m (20 ft) Steel, grade A572. 350 MPa (50 ksi)

Central concrete corc. 62 lo 28 MPa (9000 to 4000 psi)

400. 500, 660 mm (16, 20.26 in.)

r is a 50-story office building located at Madison and 1 (Fig. 4.104). It is a point lower, with multiple set- recalls the sculpturally expressive skyscrapers of the 1990s. It is clearly organized as a square floor plen

and column-free office space (Fig. 4.105).

Fig. 4.104 181 \Veal hlidiron Slrccl, Chicngn, illlnoi~


181 West Madison is the tallest combination core building in Chicago. The central concrete core is surrounded bv a sWctuml steel frame and a com~osite floor svstem. The squa~c core is 50 stories tA11. for a totnl height of 207 m (680 fi).

rile core and columns a the base of ihc building are rupponed by cnissons and gradc heams. Of the cnissons in the uroiecC 25% existed. Transfer-crade beams between new and existing cnissons were uskd io take the tower's wind an; gravity loads. The foundation wall on the east side of 181 West Madison required underpinning as it is a com- ;.?&$ mon wall with its neighbor, 10 South LaSalle StreeL

Interior spans of 13.1 m (13 ft) ailowa column-free interior space for maximum user flexibility. The many setbacks at the top of the building require all the perimeter columns to be fransferred several times. In addition, the columns on either side of the

, sect. 4.41

I I I I I I

Tubular Systems

-

-

@? loading dock at ground level are also transferred to increase clearance for trucks. E

stcel is less than 59 kg/m2 (12 psO.

lobby. Clad in warm white, grey, and green marble, the lobby's

-

- - I-+ - I I I I I I I

Fig. 4.105 8th to 14118 noor rramine pian; 181 \Vest hlndirun S t r c c ~


AT&T Corporate Center Chicago, Illinois, USA

Architect Skidmore Owings and Mcrr i l l

Structural engineer Skidmore Owings and Merr i l l


Height from street to roof 270 m (886 R ) Number o f stories 6 1

Number o f levels belo\%, ground 2

Building use Ofl icc

Frame material Conlpositr slccl-concrete perimeter liarlie. steel interior columns. stccl floor beams

Typical floor l ive load 4 kPa (80 psr) lct,cls 3 to 30: 2.5 kPa (.iO psi) Ic\ ,c~s 31 to 59

Basic wind \,elocity 35 mlsec (78 rnplt). IOU-yr return Maximunt lateral deflection HI700

Design fundantcntal period 6.5 sec

Design acceleration 20 rng. I O-yr return

Dcsign damping I to l.5<> aurrice;lhility

Earthquake looding Not applicable Type o f structure Exterior concrcte-fromcd tubc with ilite-

r ior frfieity-luad culunins. t m r r s . :lnd be i~o~s

Foundation conditions 18 m (60 i t ) o f clay over liardpan Footing type Belled caissons on 1iardp;ln

Typical floor

Story lheigltt 4.0111 (13 ft 2 in.)

Truss span 14.6 m (48 i t )

Truss depth 914 rnm (36 in.)

Truss spacing 4 . 6 m ( l 5 I t )

Illaterial Steel. grade 230 and 350 h,IP;1(36 and 50 ksi)

Slah 63-nun (1.5-in.) light\\,cight cuncrctc on 76-mm (3-in.) o~etal deck

Columns

Size at ground l loor I422 by 813 oim (56 by 32 in.)

Spacing 4.6 ~n ( 1 I 5 111

ivlnterial Nornt;il-\\,cigltt concrstc, 56 tu 35 MP;t (5000 to SUOU psi)

Cure Steel he;~ms and columns for gravity load only

Tlte ATSlT Cnrporatc Center (Fig. 4.106) consists o f a 61-story ufl icu to\i,cr \\,it11 rentable areas o f fluor plates ranging front 3250 m2 (35.000 1'1') on the lowest floors to


. . Fig. 4.1116 ATST Corpunltc Ccntcr, C ~ I E I ~ ~ C ~ . Illtnots. (Pimr<l I,?. Hrdrir i~-l( lcirbi~.~ I


Fig. 4.108 Gctwgio P I I E ~ ~ C . Atl lml~, Gcorgiu.

I# Sect. 4.41 Tubular Systems

~

TYPICAL HIGH-.RISE M O R

TYPICAL LOW.RISE. F L W R

Fig. 4.lllY Typirni flours; Gcorgio Pocific.


222'-0"

Fig. 4. i l l l Pruming piun; Gcargiu Pacific.

Fig. 4.111 Snalooth locnde; Georgia Pneilic

450 Lexington Avenue New York, N. Y., USA


Architect

Structural engineer Year 01 completion Heighl from street to roof

Number 01 stories

Number 01 lc\pels below ground

Building use

Framc malerial


hlaximum lateral dencclion

Design lundnmental period Design acceleration Design damping

Earthquake loading

Typc of structure


Footing type Typical noor

SIOV height

Bcnm span

Beam depth Beam spacing Malerial Slab

Columns Spacing Material

Core

[Chap. 4

Skidmore Owings and Mcrrill Olfice of Irwin G. Cantor

1992

168 m (550 h)

40

0 Olfice

Steel

2.5 kPa (50 psfl 36 mhec (80 mpit)

HljOO, 50-yr rcturn

5.5 sec Less than 20 mS peak 1 Su

No1 opplicablc

Perimeter tube with broced core

Rock. 4- to 6-hlPn (40- to 60-lon/lt') capacity

Piers socketed into rock

3.81 m(12116in.) 13.4 m (44 fi) 460 mm (18 in.)

3.05 m (10 11)

Stccl. grade 350 MPa (50 ksi)

64-mm (2.5-in.) concrete over 76-mm (3- in.) metal deck

6.1 m (20 11) Steel. grade 350 hlPa (50 ksi)

Braced steel. grade 350 hlPa (50 ksi)

Placing n high-rise tower abo\'e a landmark post olfice structure which sits dirrclly above a mnjor urban rail line is a highly formidable task, which requires an unusual and innovalive engineering concept. The 450 Lexington Avenue building (Fig. 4.112) is such o project and posed many challenges to lhe designers and conlractors.

Thc existing landmark post ollice sits directly over the railroad tracks leading into New York City's Grand CcnIr.nl Station. The congested system of tracks made it impossible to bring t l ~ e 54 totr'er columns down to the loundation. In addition, the track layouts ~otelly precluded the placcnlenl of a conventional a,ind resisting system due lo

Tubular Systems

terference wilh train clearances. The key to the structural solution was the use of a egacolumn syslem. The megacolumn system lonns the "legs of a table," which carries e tower's gravity and wind loads within the existing building's shell (Fig. 4.113).

Tlte megacolu~il~~s are placed 24.4 m (80 11) apart in the north-south direction and 1.8 m (170 11) apart in the east-west direction. Two are 6.1 by 7.6 m (20 by 25 ft) in

p an. and two are 6.1 by 2.6 m (20 by 8.5 11). The plan sizes were governed by the avail-

Fig. 1.1 13 450 Lcringlon ,\venue. New York.

Sect. 4.41 Tubular Systems 223 I able space bcrween tracks. The megacolumns arc solid reinforced concrete as they rise from tltc foundation through tlie train area. At the first floor. theu are comnosed of a I steel-fr3mud iruhs stru:tdre t01:111) enc3scd in cu,!crets. ~ . i t t ) Jioicrtrinn\ :i. ~UIL.U.

R ' i ~ n r tu the third-flour -u~cc . t h ~ . m e e : t ~ ~ I ~ ~ n t ~ s conne:t to rnas\trc 76-11] 25.11,- 1 - - tall trusses. The trusses estcnd in both the nonh-south and east-rvcsl directions and connect all four megacolumns. Tlie resulting megaframe systcm was referred to as the "table ton."

I t wa; the table top which picked up all the tower's columns and transferred their load to the mcgacolumns and to 13 strategically located con\'entional steel columns. The 12 intermediate columns reduce the truss spans bet\\,een llte megacolumns and aid in thc sunnon o f zrauitv loads. Ultimatclv it was this frame which transferred all the , , L .

nind I tv~Jr illid gr3$it! Iu~JI to llle fo~nd~ l iuns . I l re t lu\~hi l i ty n l \IL.L.I mxdc i t the choice m3teri~1 for 111~' luaer illttl lhc hdlk u f the

merasustem. However. the concrete encasement added the needed mass and stiffness.

tween the adiucent train tracks iormcd concrcle wall columns. Composed o f 55-MPa (6000-psi) concrete. these walls supported the intcrmcdiate columns of thc mega truss system above. Utilizing concrctc meant that the construction could proceed while the existing building above !\,as still in plnce.

Tlie towcr.5 structural svstcm is cornnosed o f a oerimetcr tube of columns naced at 6.1-m (20-it) ccntcrs. The colunins arc W36s and W30s for maximum efficiency. The four corners of the pcrimotcr tube arc reiniorccd wilh a vertical Vierendeel truss. \tshich stirfens the tube sienificuntlv. Inside the corc t\\,o vertical trusses are locrttcd. \\,hich rise

Tltc to\ve;'s lrasc suacc beeins at the sixth floor. ~ e l o $ i the sixth floor. a11 the tow- - cr's columns slope through tlic fiftli-floor mechanical area to positions upon the top chord ofthe megutrussea. Figure 4.1 I 4 illustrates thc thirteenth through thirty-fin1 odd floor framing plan.

Rccagnition that the existing past office facility is a national landmark mcont that the facade had to be maintained in its current form, whereas the central area of the existing structure was demolislied lo make way for the new mcenstructurc. Consequently Lhe facade and one adjacent bay of the structure were left inplace, thereby providinf the sla- bility to the facade while demolition and construction proceeded. The remaining bay of the existing structure \\,as known as the "douohnut" area. which \\.as uperaded struc- - . - turalty ;lnd ulum;ltcl! \<as ~nct~rpur;!tsd ialln lhc fin;ll ,Iruclure.

Tllc p l i !s~c~I ctlniple~itg :~nd ltttric;tlc compnsIt~. bcliaviur UI t l l ~ n l c g ~ ~ ) s t c ~ ~ i IU-

qtlirud ihc use .>i a n u ~ ~ t l ~ c r oi three-dimtnsiond cump.ller models for 3n3lysi. L;ilr.r:ll a.nd vertical movement bad to be determined accuratciv due to tlic imnact u&n the [and-

ihe 90-year-old bunts and limcstonc perimeter. I

226 Lateral Load Resisting Systems [Chap. 4 Tubular Systems 227

As tall buildings become more slender, the dynamic behavior of thc building bccomes more critical. The results of the wind tunnel tests showed that the Mellon Bank lower (Fig. 4.1 15) had a vortex shedding problem with the cross-wind structural response being 50% larger than the response due to the code wind forces.

A comoarison of various ootions for sliffeninr and damninr the svucmrc rvas stud-

. perimeter column system coupled with s composite steel pnd concrete supertruss wrrs

,

utilized. Figure 4.1 I6 shows the resultin% floor plan. The concrete encasemenl of the steel structure provided the needed damping, stiff-

{ ness, and additional strength. The cost analysis performed by the construction manager proved that the composite system resulted in a more economicnl structure lhan an all- - . "

led and t l~e custs ofuach method were estimolcd. I t ass C O I I C I U ~ L . ~ 11101 111s L ~ S S of:! corn- 1 .%', stccl building. Thc inter3ction of stcul nnd concrclc and their bchwior under the dcslgil posits struclural systsm would bc most eco~tomicnl. Conwqucntly a concrr.lc.uncared ?:' loads were studied utilizing a detailed finite.elemunt nnalysis.

The building's lateral system is formed by the comoosite nerimeter columns soaccd 7.95 m (9 11 B h.) on ccnlfr, forming a pcri&eler l ubC[~ ig . i .117). Typical composite column xhemes ulili7.c the slecl columns sol:ly fnr erection purposes, uith the bulk of thc v~.rticaI load carried by the concrete. In this slruclure, restrictions in the overall s ire of the columns required the use of a truly shared composite system, with the concrete encasement and the steel columns each c a w i n g significant portions of the vertical load.

,

F i g . . hl~llnn Dunk. Philodrlphin, Penns?.lvaniu. .:::. .. . , Fig.4.116 Framing plan for noors 14 l o 23; hlcilon Dank. .* , . - , .,>A. ,., . ... . .,i?.. .,.

Sect. 4.41 Tubular Systems 229

Comolicatine the nroiect was that none of the 52 columns in the tower continued di- - . . rectly to the ground. Instead, all of the perimeter columns are either sloped o r picked up bv msses. The sloped column system enabled the transfer of columns into new positions, allowing for the enlargement of the lower floor plates while still maintaining col-

,:.u.mn-free 2.. . lease space. *.. , . - I Depending on the architectural constraints, groups of columns slope at different

floors. The sloped columns always form a symmevical system, whereby sloped columns on opposite sides of the floor balance out the overturning forces resulting from the slope. In numerous cases, columns are terminated upon pick-up tmsses, which are also sloped to link up with their repositioned supporting columns.

A unique sloped column system occurs between the tenth and thirteenth floors, where the four inside comer columns are supported by an A-frame. Each A-frame generates significant lateral forces, which are all balanced out by again balancing one corner against the opposite corner. The floor diaphragm, being the link between all columns, plays a kcy role in transferring these balancing forces across the floor. The mosi critical diaphragms arc the fifth- and sixth-floor diaphragms where, in addition to supporting most of the sloped columns, the lateral wind forces are transferred from the nerimctcr to the core vertical w s s . r

With some slopcd columns generating 7000 liN (450.000 lb) in lateral force, the de- signer chosc lo place a 13.4-111 (a-ft)-deep steel horizontal truss within the floor dian-hraam. ~hese ' trusses helo transfer the b ind forces to the core while passing the ~~r~~~~ - sloped column forccs around the core to the opposite sloped column.

At the core a vertical supertruss extends from the foundation up to the sixth floor. The supertruss is constructch of steel wide-flange shapes, with the four comer columns encased in 3000- by 3000- by 600-mm (10- by IO- by 7-ft)-thick L-shaped concrete shear walls, thereby forming a composite steel nnd concrete supenruss. The supenruss is divided into two parts, a large 13.7-111 (45-ft)-high truss between.levcls 6 and 3, and a single X truss on each face of the core, extending from the third level down to the foundation.

The transfer of latcral loads out of the oerimeter and into the core at the sixth floor forntr an optimum conibin3tinn 01 the core and perimdtcr 1stur:il system,. Triinjfcmng the wind lateral force\ to the core ;it ilie r i ~ i h flour results in zero uplilt forccs upon the foundations.

I-+&&+.. Fig. 4.117 Eurl and west lncrr of pcrirnelcr tui,c: i\lcllnn Dunk.

230 Lateral Load Resisting Systems {Chap. 4

Sumitorno Life Insurance Building Okayama. Japan


Year of completion Height from strcet to roof Number of stories

Number of levels below ground Building use Frame material

Typical floor live load Maximum lateral dcnection


Design damping




Story height

Beam span Beam depth


Slab Columns

Size at 2d floor Spacing

Moterial Core

Nikken Sekkei Ltd.

Nikken Sekkci Ltd.

1977 75.3 m (247 ft) 21

2 Office

Structural steel from 4th noor up: concrete-encased structural steel and shear walls below i t h noor

3 kPa (60 psO Not available

2.08 sec transverse: 2.01 sec longitudinal Level 1 EQ, 20 mg; level 2 EQ, 25 mg

2% C = 0.14

Structural steel perimeter tube from 4th floor up: arched conciete-enca5ed steel fnrncs and shear u-alls from ground to first noor Gravel Raft

3.5 m (1 I ft 6 in.) 9.9 m (32 ft 6 in.)

700 mm (27.5 in.) 2.5 m (8 f t 2 in.)

Steel, grade 400 MPa (58 ksi) 150-mm (6-in.) concrete on metal deck

400 by 300 mm (16 by 12 in.)

2.5 m (8 ft 2 in.) Steel, grade 190 MPa (70 ksi)

Steel frame

The main structural system of this building is a nearly square tube structure, which em- ploys a peripheral frame in an integrated fashion (Fig. 4.1 IS). In appearance, tile tube structure has no directionality. The peripheral hearing walls of the l'irst and second floors support the upper structure a ~ i d have a large arcli-shaped opening. The axial forces of the external columns of the upper tube structure are transferred by the nrcli-

! . Sad. 4.41 Tubular Systems

Fig. 4.118 Sumito~no Life Imurnncr Building, Okoynmo, Japan,


shaped bearing walls of the first and second floors to the L-shaped wall columns at the four comers and thence to the foundations via bearing walls below grade.

The arch-shaped bearing walls of the first and second floors are of reinforced concrete construction with internal steel msses (Fig. 4.119). The embedded steel structure is designed to remain elastic for long-term vertical loads and for short-term horizontal loads. The bearing walls were modeled as flat plates and analyzed by finite-element analysis. (The steel msses were taken into consideration.) Analysis of the earthquake response was performed using a rnultimass model, which combined the upper tube struchlre with the arch-shaped bearing walls of the fust and second floors. For accelerations of 3500 mmlsec2 (1 1.5 ftlsec2) during a large ennhquake. the arch-shaped bearing walls remain within the allowable elastic stress range. The primary natural period in the vertical direction (considering vertical rigidity of the arch-shaped bearing walls) is 0.179 sec, so there was almost no response from the arch-shaped bearing walls due to venical earthquake motions.

The typical floors (Fig. 4.120) are supported by 700-mm (27.5-in.)-deep trusses at 2.5-m (8-ft 2-in.) centers spanning 9.9 m (32 R 6 in.). The spnces between the truss web members allow for the passage of ducts and pipes. The truss top chord is connected via stud shear connectors to the concrete slab. The increase in stiffness results in a frequency of vibration of h e floor in excess of 9 Hz.

Tubular Systems

Fig. 4.119 Fmmcnork; Sumitomo Life Inruruncc Building.


. . . . . . . ..

Fig. 4.1ZU Txpicul structurui flour pins; Sunnitunls Lilc lniurdnru Uuilding.


Dewey Square Tower Boston, Massachusetts, USA

Architect Pietro Belluschi Inc. and lung Branncn Associates Inc.

Structural engineer Weidlinger Associates


Height from street to roof 182 m (597 ft) Number of stories 46


Frame material Steel Typical noor live load 2.5 Wn (50 psf) Basic wind velocity 42 mlsec (95 mph) Maximum lateral deflection 450 mm (I8 in.). 100-yr return Design fundamental period 5.5.4.3 sec

Design acceleration 23 mg peak. 10-yr return Design damping I % serviceability: 2% ultimate Earthquake loading Not applicable

Type of structure Perimeter tube Foundation conditions Stiff silty clay over compact glacial till Footing type Mat. 1800 lo 2600 mm (6 to 8 ft 6 in.)

thick Typicnl floor

Story height 3.81 m (12 ft 6 in.) Beam span 9.1 m (30 ft) Beam depth 400 mm (16 in.) Beam spacing 2.3 m (7 ft 6 in.) Material Steel

Slab 133-mm (5.25-in.) lightweight concrete an metal deck

Columns

Size at ground floor W350 by 1088 kglm (W14 by 730 Iblft) Spacing 4.57 rn (15 ft) Material Steel, grade 350 MPa (50 ksi)

Core Braced steel frame, grade 350 MPa (50 ksi)

After having examined many alternative systems, project designers at Weidlinger As- sociates concluded that a steel structure with a rigid frame around the perimeter was most economical for this 46-story building and would resolve the requirements for in- tegrating the structure with the curtain wall (Fig. 4.121). Ressstance to wind and seismic forces is provided by the framed tubc forming the tower's penmeter. To economize


on field work, particularly field welding, spandrel units consist of trees with columns and welded eirder stubs. Field connections of the girders at the centerlinc between cnlumnr are golted shear connections.

~

Spandrel girders on lyptcal floors arc gcncrally 1143 mm (-15 in.) deep. \.:lr).ing irom a minimum or900 mm (39 in.) at the lop o i ihe building lo 1245 mnl (49 in.) a! lllc bol- tom. Columns are built-up members 760 mm (30 in.) deep along the building face. except where rollcd sections are used above the thirty-third floor. Perimeter columns arc

Fig. 4.121 D e w y Squure Tower, Boston, hlnrsnchusctb. (Phoin lir S a w Rorrrirbn1.l

Tubular Systsms

arranged to provide open comers, that is, the ladder section always ends with a beam stub at the comer. This scheme avoided the complication of three-dimensional corner columns with welded stubs eoina in two directions as well as the hiaxial bending problem of a comer column. since ail of the structure's lateral stiifness is proridednr~ound the penmcter. nil interior bean-lo-beam connccliuns arc o i l he simple sllcar type.

A varietv of steels is used throuehout the struclure. Exterior columns and inlerior - ~:&floor framing are of A-36 steel, girders and interior columns are A-572 grade 50, and

built-up interior columns are g n d e 42. High-strength steels were chosen where the desien w& eovemed bv streneth considerations. Where the desien is primarily aovemcd - - - - . . . b) dcfor~nalion criteria. as for drturiur columns, lower-strength l e e i s ware oscd.

The lower has o slructural dcpth u i 36.57 m (120 it) ul th a height-lo-depth ratio of almost5:I. This. couoled with its unusual shaoe. sueeested the useof a windtunnel test . . . . -- !o verify both the magnitude and the local variations of wind forces. The wind tunnel test results very closely matched the overall forces required under the Massachusetts code. Local hoi soots here found to exist oarticularlv a t the intersection between the tower and the atrium.

The analysis of the suucture for lateral forces yielded information useful for future oroiects. It is well known that the effect oishear deformation becomes mnenified with an . a - increase in the depth-to-span ratio of the beam. Since in a frame such as this, the depth- to-span ratio is on the order of 15 . shear delormations contribute a large part of the total lateral deformation of the swcture. Soecificallv. in this case it was found that the lateral deflection due to drift of the buildingLan be aGibuted in roughly equal parts to:

Overall deformations of the frame (shear deflections)

Column shortening (bending defleclion) Shear deformation of beams and columns

Since the girder webs are relatively thin compared to the column webs, the major portion of the shear deformation is attributable to the beam web.

Wherever possible in the eslablishcd program, the steel fabricator elected to substi- tute fillct weldine for this connection between the spandrel eirder flanees and the - - penmuter columns. This was cltoscn w c r the specified full-pcnclmlion weld.

\VBcnevcr the ercction equipment uouid nllo!, . the iabricnlor uscd 1-0-stor). tiers for !hi. e~ter ior columns. There cunsisted of the lull 7.62-m (25.11) columo. ~ i l h tuo sp;in- drel girder stubs oo each side. The spandrel girders were then bolted togcthcr nl mldsp~n This method kept field \$,elding to 2 m~nimum as well ns expediting the erc:tlon

In erectine the steel tower, three self-climbine tower cranes were used in lieu O F the - - more conventional two. This ensured maximum erection speed and facilitated the ercction of the precnst concrete panels, also pan of the steel contractor's work. Dewey Square Tower is granite-clad on the lower two floors, with precast rain-screen panels reachine from the third floor to the s l o ~ e d class crown of the fanv-sixth starv. Contin- - . - uous bands of tinted reflective glass alternate with bands of exposed granite aggregate set in white cement. S l ~ c t u r a l connections for the panels were dcvclopcd wilh input from both the panel fabricator and the steel contractor. The typical panel is attached by two load-bearkg connections and two lateral connections shop-welded to the perimeter columns. Floor construction consists of a 50-mm (2-in.) composite deck with an 83-mm (3.25-in.) lightweight concrete topping.

The torvcr starts on a concrete mat two stories below erade and rises 180 m (590 it). . f l ~ s I t - ru 2-m (6- to 8-frl-(hick concrete m:ti reris on hardpan, nhi:h protrdcr ; ~ n eco- nnnli;;ii i b ~ n r l ~ t i u n Tilt are;, uf lhr. building surro~nding thc i.>\\cr 113s cnlumns rdsting on spread footings and incorporates an undcrdrain system below the subbasement slab.


Morton International Chicago. Illinois, USA


Year of completion Height from street to roof Number of stories

Number of levels below ground Building use Frame material


Design wind load deflection Design fundamental period Design acccleration

Design damping

Eanhquake loading Type of structure


Typical floor Story height Beam span


Material Slab

Columns


[Chap. 4

Perkins and Will

Perkins and Will 1990

170 m (560 ft) lo top of clocktower 36 plus clocktower 1

Office, parking, and retail S l ~ ~ t ~ r a l steel

2.5 W a (50 psfl 34 mlsec (75 mph) 330 mm (13 in.). 50-yr return 4 sec Estimated 15 mg peak, 10-yr return

I lo serviceability Not applicable

Perimeter framed tube with transfer truss at low level Stiff clay

Belled caissons bearing on hardpan

3.81 m (12 ft 6 in.) 12.6 m (41 f t 6 in.)

533 mm (21 in.)

3.05 m (10 ft) Steel, grade 350 MPa (50 ksi) 140-mm (5.5-in.) lightweight concrete on steel deck

Built-up 1640 kglm (1100 Iblft) max

4.57 m (15 ft) exterior; 9.1 by 12.6 m (30 ft by 41 f t 6 in.) interior

Material Steel, grade 350 MPa (50 ksi) Core Steel frames supporting gravity loads only

The Morton International building comprises a 13-story base containing commercial floors and parking for 450 cars, topped by a 23-story ofice tower (Fig. 4.122). The site fronts the Chicago River and contains existing railroad tracks, which had to remain fully operational during consmction. Almost a quarter of the site was unable to accommodate any footings and the remainder rcquircd large spans across the tmcks. Several interesting transfer systems were designed lo overcome the site restraints.


The 36-story structure has typical floor spans of 12.6 m (41 ft 6 in.). but spans varying from 19.8 lo 21.3 m (65 to 70 it) were required to span the railroad tracks. This was achieved with n series of 6-story-deep Vierendeel frames consisting of two 3.05-m (10- ft)-deep plate girders, one at level 2 and one at level 8, connected by fully welded vertical and horizontal members. For a building of this height, a braced core would have been the obvious means of resisting wind loads. However, in lhis case the railroad tracks

Pig. 4.122 Morton lntcrnnlionol. Chicago, lliinoir. (Plzoro I,? Hrdrich-Blerring)


made this impossible and instead, a perimeter framed tube with columns at 4.57 m (15 ft) was adopted. The columns and spnndrel beams were shop-fabricated into 2-story- high "ladders" with site-bolted web plate connections at midspan of the beams. This design saved 1360 tonnes (1500 tons) of steel compared to an original design with perimeter columns at 9-m (30-fl) centen.

The 13-storv structure presented major challenges, which were overcome by three separate transfer structures and unusual construction rrquirrmcnts. Street-level concrete transfer beams 2.3 m (7 ft 6 in.) deep nt 9-m (30-it) centers span the mcks lo allow a regular and efficient column setout above.

The recond transfer svstem occurs above the roof to the southern end of the build- ~~~~~~-~

ing, where no footings were able to be provided in the tnck zone. Trusses with major members built uo from six 100- by 600-mm (4- by 24-in.) plates suspend one side of the - -. . -. . . -.

n l e third transfer system occurs between levels 2 and 4 and serves to redirect two rows of upper columns into one row located to avoid the tracks. The entire vrnical structure above these transfer frames uas erected to the roof lcvel, and the roof top trusses were erected cantilevering bcyond the floors belon. This section of thc bullding was erected 90 rnm (3.5 in.) out of plumb to dlow for the sway induced when the can- tilewred section was erected and partially loaded.

With the roof top trusscs erected, perimeter columns wrre suspended ham the free ends of the trusses.and the floors were erected in a conventional manner from the bol- tom up. To equalize dcfl:ctions and minimize difrcrentinl movement, a load-distributing longiludinal truss mas installed at level 8 between the suspcndcd columns.'lhis truss served 3 dual purpose in that it was also designed lo redistribute the column load to ad- jacrnt columns should aroof-top truss fail. The roof-top trusrrs were providcd u,ith suf- ficicnt capacity to allow them to cnrry t h ~ s additional load.

This challeneine proicct received an nwnrd for Most Innovative Design of 1990 from - -. - the Structural Engineers Association of Illinois

Tubular Systems

Cesnr Pelli Associates

Walter P. Moore and Associates,

1992 . ' Height from street to roof 256 m (840 ft)

Inc

Number of stories


Building use


Basic wind velocity


Design fundnmental period

Design acceleration

Design damping

Eanhqualie loading

Type of structure Foundation conditions

Footing type


Beam span

Beam depth Beam spacing Slab

Columns Spacing Material

62

2

Oftice, corporate headquarters, retail

Concrete 2.5 kPa (50 psf) + 1.0-kPa (20-pst) partitions 35 mlsec (80 mph) at 10-m (3341) heighl

HnOO, 50-yr wind

5.3 sec

12 mg peak, 10-yr wind

1.5% serviceability; 2.5% ultimate

C = 0.53, Z = 0.15. Ru, = 7.0 intermediate moment resisling frame (IMRF) Perimeter tube

Clay of variable thickness, 4.6 to 7.6 m (15 lo 25 it) over weathered bedrock

2.4-m (8-ft)-thick core mat on weathered rock: 9- to 30-m (30- to 100-it)-deep caissons (150 ksO. 1.5 to 1.8 m (5 to 6 it) in diameter

3.86 m (I2 ft 8 in.)

14.63 m (48 ft)

457 mm (18 in.) posttensioned

3.05 m ( I0 it) 117-mm (4.625411.) lightweight concrete one-way. 35 MPa (5000 psi) 1370 mm (54 in.) in diameter

6.1 m (20 ft) 55 MPa (8000-psi) concrete

The Nations Bank Corporate Center is a 60-story. 256-m (840-fl) tall building in the central business district of Charlotte. North Carolina (Fig. 4.123). The building is the tallest in the southeastern United States and will dominate Charlotte's skyline into the 2151 century. From a heavy stone base, the building rises with curved sides and pro- gressive setbacks culminating in a crown of silver rods symbolizing Charlotte's nick- name, "The Queen City." The exterior surface materials arc rcddish and beige granite


and mirrored reflective glass; the granite piers narrowing at each setback. The building will serve as the corporate headquarters for Nations Bank.

A number of different feasible structural schemes were analyzed before Nations Bank and the developer together selected an economical concrete frame. A reinforced . - concrd~c frame U 3 S ssl~ctcd bec3use it met both thc intricate geumetric rcquiremsnt, 01 thr. arcl~~tucr ;~nd the d-munds of the detcloper for economy Sh3llow posttensioricd concrete floors were used to span the 14.6-m (48-ft) lease depths and to achieve the desired 3.9-m (12.5-ft) floor-lo-floor heights.

Fig. 4.123 Nutions Bunk Corporule Ccntcr, Ci~orlstle. North Cilrollnu.


The smctural system selection followed an intensive four-phase scheme development process. This process has been used successfully in swctural system selection for many other high-rise projects. The purpose of the structural scheme selection process is not only limited to finding the most economical structural system. but to finding the system that best resoonds to the overall buildine eoals. Nonswctural oorameters such as

u - impact on lc~sing, column sizes and locations, shcar wall drop-offs, construction dura- tion, floor-to-floor heights, fire nling and intcgrntion wilh mechanical systems arc also considered. The entire-team oaiicio&d in theselection orocess

Thr. srleclcd all.concrcte scheme consists of a reit~forcud concrele perimclrr lube struculre witl~calum~is spaced on6.1 rn (20 ft)centers.Thc perimeter lrwnr utilizes normal weleht concrele with slrenclhs rancinc from 41.300 lo 55,000 Wa (6000 lo 8000 psi). ~h;external tube was selected because it was the most efficient late& load resisting system. The tube also proved to be an economical method of dealing with the many setbacks and column transfers imposed by the building architecture. The floor system consists of a 117-mm 14.5-in.)-thicklichtweieht concrete slab soannine to 457-mm (18- in.)-deep post-lension;d beams. The pasttenzoned beams are spaced on 3 m (10 ft) =en- ters and span as much as 14.6 m (48 it). The 14.6-111 span provides column-free lease soacc from the core to lheperimeter.The shallow structural devth allowed the low floor- to-floor height resulting in additional savings in skin cost. ~ i ~ h t w e i g h t floor concrete was selected to minimize the building weight and to achieve Charlotte's unusual re- ouirements for 3-hr fire separation. A normal weirht concrete slab would have needed - lo be I50 mm (6 in.) tltick in order lo proiidc tlie Err. separation, substantially incrcas- ing not only the b~ildlng wcighl but also ths floor-lo-floor hcight.

All lateral loads are resisted hv the external frame. The floor framinn and core - columns 3re sized for gravity loads. Lateral load niumcnls imposed by compatibility uf deformation uilh the cxtcrior frame were found lo bc ~nsignificanl. The corc columns were shaped to be wall-like Column sires ranecd from 0.6 by 5.5 m (2 by 18 it) at the lower le&l to 600 by 900 mm (24 R by 35 in.i at the top of the building;~he walllike colunm shapes integrated very well with the building core.


Bank One Center Dallas, Texas, USA

Architect Stmctural engineer

Year of completion Height from skeet to roof


Building use

Frame material

Typical noor live load

Basic wind velocity

Maximum lateral deflection Design fundamental period

Design damping

Eanhquake loading


Footing type

Typical noor Story height

Beam span


Material

Columns

Spocing Material

[Chap. 4 Sect. 4.41 Tubular Systems

John Burgee Architects with Philip Johnson The DatumIMoore Pafinership 1987

240 m (787 ft)

60

4

Office, parking

Concrete-composite perimeter frame, steel core

2.5 kPa (50 psO + 1.0-kPa (20-psO pnrti- tions 31 mlsec (70 mph) at 10-m (33-11) height

Hl500, second order. 50-yr wind

6.8, 6.5. 3.5 sec

2.0% serviceability; 1.5% ultimate None

Perimeter tube

6.1-m (20-ft) shnie and weathered limc- stone over unweathered limestone

design allowable

3.84 m (12 ft 7 in.) 14.69 m (48 R 2 in.)

457-mm (18-in.) 2.74 m (9 ft)

Steel. A572 grade 50.50-mm (?-in.) composite metal deck + 89-mm (3.5-in.) 1i:httveight concrete 610-mm (2-it)-square 100-mm (4-in.). thick box column 7.6 m I25 ft) Steel. A572 grade 50

Bank Onc Ccnlcr is a postmodern to!\'er compictc rvith a monumental arched entry and curved roo[ line (Fig. 4.12-1). The 60-story oflice tower also Ins an atrium banking hail in its 6-story podium, semicircular arched roofs at the t\\,ent)'-sixth floor and quarter- circle i,aulted skylights at the fiftieth, where the shope changes from rectangular to cruciform. On top is a cross vaulted arch clad in copper and pmnite.

The engineering for the 148,000 m' (1.6 million ft') project is as complex as the architecture. Extensive value engineering studies were done during design development to

. ' analyze six floor framing systems and four wind framing systems. Design information for each was provided to the general conuactor, who in turn smdied scheduling and prices.

All four wind schemes were variations of the perimeter tube. For the early compar- :alive design studies, Dallas building code wind forces were used. The selected scheme

1 :!. Fig.J.124 Dunk Onc Ccnlcr, Dallus, Tcsar


has punched concrete walls at the building corners with infills of composite columns and steel spandrels; floors have a composite steel heam framing system.

The building's nrchitecture requires a number of geometric changes as the stmctural frame rises above the below-grade levels. The cruciform shape above level 50 created two major structural problems. First, the perimeter tube had to be broken, leaving only two-dimensional rigid frames on each building facade. To control frame distortions under wind loading, two-story X-braced frames were added in the core. This required strenathened diaphragm floors to allow the transfer of wind shear forces from the - . - irames to the pcrimetsr lube system btlou. Second, comer columns at the rccnuant cor- ncrs of the cruciform hod lo be transferred lo provide culumn-free lease space bclow Icvel 50. Story-deep Vicrendccl trusses spanning 13.7 m (45 it) move these gravity column loads 10 tltc perinieter wind frame and to the cure. Because of the relationship be- t!\e:n corc and perimeter columns. lhr trusses ltad lo be supponed nt the corc by two- slury Vicrcndecl lrusscs spanning 8.5 m (28 it) to the building corc columns.

Sect. 4.41

Central Plaza Hong Kong

Architect

Smctural engineer Year of completion Height from sweet to

Number of stories 8 roof

Number of levels below ground Building use

Frame material Typical floor live load Basic wind velocity


Design acceleration

Earthquake loading

Type of structure



Story height Benm span

Beam depth

Slab Columns


Material

Core

Material

Tubular Systems

Nu Chun Man and Associales Ove Amp and Partners 1992 314 m (1030 ft) 78 3

Oifice

Reinforced concrete 3 P a (63 psfJ

64 mlsec (144 mph). 50-yr rcturn, 3-sec gust

400 mm (15.8 in.), 50-yr return period wind

Less than 10 mg. 10-yr rcturn period (typhoon wind) Not applicable

Perimeter tube and corc Fill over clay over granite bedrock; granite bedrock. 25 to 40 m (80 to 130 it) below ground

Machine- and hand-dug caissons to rock

3.6 m (11.8 ft)

12 m (39 ft) 700-mm (27.5-in.) reinforced concrete

1 6 a m (6.3-in.) reinforced concrete

2-m (6.5-A) diameter

8.6 m (28 ft) Concrete, cube strength 60 Nlmm' (8500 P") Shear walls 1.3 m (4 f t 3 in.) thick at base

Concrete, cube strength 60 to 40 Nlmm' (8500 to 5800 psi)

When completed in 1992, Central Plaza was the tallest reinforced concrete building in the \vorld (Fig. 4.125). The site is typical of a recently reclaimed area with sound bedrock lying between 25 and 40 m (80 and 130 ft) below ground level. This is overlain by decomposed rock and marine deposits, with the lop 10 to 15 m (33 to 1 9 ft) being of fill material. A permitted bearing pressure of 5.0 MPa (56 ton/ft2) is allowed on sound rock. The maximum water table rises to about 2 m (6.5 fl) below ground level.


Fig. 4.125 Ccnlrol Plnzu. Hung Kong. (Cotarrery of O w Anlp und Pnrrncrs.)


Wind loading is the major design criterion in Hong Kong, which is situated in an -& fluenccd by typhoons. TheHong Kong code of practice for wind effects is bared on amend:,

,. hourly wind speed nf 44.3 d s e c (99 mph). 3-sec gusls of 70.5 m/Sec (158 mph), and give$r, rise to a l a t e d design pressure of 4.1 kPa (82 psO at 200 m (656 h),above pound level. :!$!id,

11 was clear from the outset that a multilevel basement of mnxlmum noor area be required. The design of a diaphragm wall. extending around the whole slte perimeter,

i:f<z?md consmcted down to and grouted to rock, was completed in the firs1 week aher the site waz acquired. This enabled construction to commence 3 months later (Fig. 4.1260 to c).

17 STRUCTURE

Fig. 4.126n Ccnlrnl Plnm. Eicvnlion of building.

..,' , ,. ...

~ % .

'. -.:: ,~.,.. ~..


An initial planning assessmcnl had indicated that up to four levels ofbasement could be required and the design produced catered for this. By the lime construction commenced, it had been decided that only three levels would be necessary, and the construction drawings were amended accordingly.

The diaphragm wall design allowed for the basement to be constructed by the lop- down method. This provided three fundamcnlai advantages:

TRANSFER PLATE

A- A B-B KEY PLAN Fig. 4.126b Centrnl Piuro. Slruclurui rterl rehcmc.


Elg. 4.126~ Ccntrnl Plnm. Derign wind prrsrurc concrcte scheme

1 254 Lateral Load Resisting Systems [Chap. 4

I (1 11 ft 10 in.). The core hns an arrangement similar to that of the steel scheme and, just I above the lower base, it carries a ~ ~ r o x i m a t e l v 10% of the total wind shear. . .

Thc tnwcr b.asr slrtlcturc edge transfcr beam is 5.5 m ( I 8 it) deep by 2.8 m (9 i t ? in.) u,ids around the pc"nletcr. This allnws 3llernatc 2olumnr to be dropped from the fac;!dc. thereby upunirlg up ihc public srca at ground lcvel. The incrmsed column rpacinc, together with the elimination ofspandrei beams in thc tower base, results in tl;e external frame no longer being able to carry the wind loads acting on the building. Over the height of the lower base. the core transfers all of the wind shears to the foundations. A I-m (39-in.)-thick slab at the underside of the transfer beam transfers the total wind shcar from the cxternal fmme at the inner core below.

The uind shcx is taken out from lhc core ot the louert bosctncnt leucl, whcre it is transftrrcd lo thc punmetcr diaphragm u,nlls. In ordcr to rcducr large s h c a rc\.ersals in the core !rails in lhc bnsumcnt and nl the top of the tower basc lu,cl. thc floor slobs 2nd beams arc separated horizontally from the core wnlls at the ground floor, basement levels 1 and 2. and the fifth and sixth floors. To comolete the dramatic imoact ofthir build- . ~ ~ - ~

ing, the tower top incorporntcs a mast, which will be constructed of S l~c tu r a l steel tubes with diameters of up to 2 m (6 ft 6 in.).

The performance of tnll building structures in the strong typhoon wind climate is of particular importance. Not only must the structure be able ;isis1 the loads in general. and the cladding system and ic; fixings resist higher local loads, but the building must also perform dynamically in an acceptable manner such that predicted movements lie within acceptable standards of occupant comfort criteria. To ensure that all aspects of the building's performance in strong winds will be acceptable, a detailed wind tunnel study was carried out by Professor Alan Davenpon in the Boundary-Layer WindTun- ncl at the University of Western Ontario.

When complelcd, this project became the tallest reinforced concrete building structure in the world. For such a tall building it is not appropriate to adopt the strength of

tbl J 4

Fig. 4.127 Central Pinm. (n) Typlcol of icc noor plum. (b ) Foundnllom. (Continued)


materials commonly used for normal buildings in Hong Kong. In ordcr to reduce the size of the vertical structure it was decided to use high-strength concrete 128-day cube strength of 60 MPa (8500 psi)]. This is the first private-sector development in Hong Kong for which approval has been granted by the Hong Kong building authority forthe use of such a material. Considerable research took olace into materials and mix design. - and man) t r i i s were ~3rrir.d OJI, includtng mock-ups of the large-diamcler columns to check on icmperaturc uffccls. As n result ofthis, cooling was introduced into the major pours.

The use of hirher strcnrths was considered. but it was decided against it since it was - - - conidtrcd by the dt\,r.lopment team thlt the material chosen could bc produced without difficult) front matcri=ls readily wailsblc in llong Kong.


Hopewell Centre Hong Kong

Architect

Structural engineer

Yevr of completion Height from street to I O O ~

Number of stories


Building use

Frame material Typical noor live load Maximum lateral deflection

Design acceleration

Earthquake loading

Type of structure



Story height Bcam span

Bcam dcpth Slab

Columns

Size at ground floor

Spacing

Material

Gordon Wu and Associates

Ovc Amp and Partners

1980

216 m (708 ft)

64 1

Offices above parking and commercial podium Rcinrorced concrete

3 kPa (63 psfl

150 mm (5.9 in.). 50-yrrctum period wind

16 mg peak. 2-yr return period Not applicable

Pcrimctcr tube and inlcrnul core

Srrund granitc very close to cround level Pad footings an rock

3.35 m ( l l . 0 f t ) 12.3 m (40 It) 686-mm (27-in.) reinrorccd concrete 100-mm (5.9-in.) reinforced concrete

1 A5 by 1.22 m (4.75 by 40 fi)

3 m ( 1 0 f t )

Concrete, cube strength 40 Nlmm' (5800 psi) . Shear walls. 762 mm (30 in.) thick at basc; circular in plan

Material Concrete, cube strcngth 40 Nlmm' (5800 psi)

The I-lopervell Centre is situated on a steeply sloping site, one entrance being at ground floor and asecond main entrance to the rear of the building at the seventeenth floor (Fig. 1.128). The tower itself is rounded on pad footings at levels varying between the underside o r the basement and the third noor. Stability is principally providcd by thc perimeter tube structure rormcd by 48 columns at a spacing o r 3 m (10 ft), linked by 1670-mm (66-in.)-deep spandrel beams at each floor levcl. Some assistance is also provided by the internal corc. Shears nre transferred to the foundations at the third-noor level through a 157-mm (19-in.)-thick noor slab (Fig. 4.129). The entire verdcal structure was constructed using slip-formin€ techniques. The main office floors use a radial h u m and slab system and were formed using fiberglass molds (Fig. 4.130). Uring these techniques, construction progressed at a rate of 4 days a floor.


> . Fig. 4.128 Hoperell Ccntrc, Hong Kong. (Colmcry o/Ol,e Antp nnd Porrnrrrl

(. i .~,:. !.+ 24. xi


224m rndiul r 1 i


PROJECT DESCRIPTIONS. TRUSSED TUBES

First International Building Dallas, Texas, USA

Architect

Slructural engineer

Year of completion


Numbcr of stories



Typical floor load Basic wind velocity

M a i m u m lateral deflection

Earthquake loading

Type of structure


Footing type

Typical noor Story heigbt

Beam span Bcnm depth

Beam spocing Slab

Columns

Size 31 ground noor

Spacing

hlatcrial

Hcllmurh Obata and Kassabaum. Inc.

Ellisor and Tanner. Inc.

1974

217m (714 ft)

56 2 office

Struclural steel

2.5 kPa (50 psn

31 mlscc (70 mph) Hl500.50-yr rcturn period

Not applicable

Trussed tube

Limestone. 4.3-hlPa (-IO-ton/ft2) capacity

Spread footings

3.81 m (12 ft 6 in.) 12.27 m (40 f t 3 in.)

460.530 mm (18, 21 in.)

3.81. 10.97 m ( I? It 6 in.. 36 ft) 83-mm (3.25-in.) lightweight concrerc on 76-mm (3411.) metal deck

533 by 584 mm (21 by 23 in.) -7.62 rn (25 it)

Steel. gmdc 350 hlPa (50 hi)

The 56-story First Internnlionnl Building with a Ihcighl of 2 17 m (71-1 i t ) lhas 176.500 m' (1.9 million TI') of space (Fig. 4.131). There are an adjacent 13-story scli-perk gerngr and a 10-station drive-up banking facility. Tendcm clcv;~tors llandle the venical movement of building occupants during peak traffic pcriods. Each of the 2-1 passenger cleva- tor shafts has two elcvalar cabs, mountcd one on top of the other and moving on a single set of cables.

Thc exicriar dimensions of the onice tou.er arc 55 by 55 m ( 1 8 1 by 181 it). The sx- terior column spacing is 7.62 rn (25 ft). Thcrc is n column-free span irom the core to the exterior columns of 1227 nt (10 ii 3 in.).

The design incorporalcs the trussed lube struclural syslcni in the exterior frame, utilizing large X braces, each covering 28 floors. two lo a side. Because nftlte usc of large X-bracing clcmcnts on the four exterior \valls to resist lateral wind forces plus some


Fig. 4.131 Firs1 lnternolionni Uuilding. Dullas, Tcxor,


eravitv loads. wind fmmes or msse s in the interior core are eliminated. The two X - . breccs on each side consist of diagonal steel wide-flange mcrnhrrs whose ouuide dimensions arc approximalcly 610 by GI0 mm (24 by 24 in.). The gusset plates art approximately 3 m (10 ft) wide and 3 6 m (12 it) tall (Fig 3.132).

Comer box columns 610 mm (24 in.] sauare are used in the basement and are fabri- . . cated from 152-mm (6-in)-thick stucl plates. These Inkc the henvieit loods accumulat- ing from the diagonal bracing of two ridrwnlis. Tlts comer gusset asscmblics a r t L- shaped in section and were welded by the electroslag process.

Another structural design concept is the stub-girder system. This minimizes structural costs lhroueh a reduction in the amount of steel reauired far floor framing and a - ~~~ ~=~~ lessening of the building's floor-to,floor hcight. The built-up girder system consins of stubs that arc fabricated onto ruucturnl beams (Fig. 4.133). nts \ride-flange beam acts as a bouorn chord whcrcas lhc rhorl slubs act ;is u e b mumbcrr.'Ths 159-tnm (6.3.in.) liehtweiaht concrete slab functions in com~osi te action with h e steel or the too chord. The overall effect is that the slab and beam'function as flanees. whereas the stubs func- - ~ . ~~ ~~ ~~~ ~

lion as wch struts in a Vicrcnducl truss. Ills stub girders p~.rmit unubrrrucrud runs o fmc- chanical ducts without web openings in llic beams. n ~ e y also suppun the scmicontinu-'

~ - . . our floor beams.

An electrified floor svslem was used for the first time with the stub-eirder conceot. L ~~- - .

Alro, a longer girder is uacd than in prcwous applications of the s)slr.m. In addition to I! detailed cumputer anslysis of the stub.girder design for this project. actual load tests were made to funher verify the desien concept

The buildine was tonoid out i n 6 6 weef;; from rroundbreakine and in 10 months - . . - - ~

from the erection ofthe first piece ofsuuctural steel. Tlti; projcct recui\ed ~ l i c first Con- suiting Eng~nccrr Council of Texas "Emincnt Conccplor Award for the h l o n Outsv,md- ing Engineering Project" in 1974.

i E


_I o 7 spaces at 7 25'4" = 175'4'' -3

Wlnd oracing in exter or frames t,p ca ai 10-r s oes


.I 0

3'4'' k- 7 spaces at 2 5 ' 4 = 175'4"-4 Ic

9 Tvoicai low rise floor lrarnino oian 'n

Mechanical duct

7 6114"

W14 girder (ASTM A572 GR.50)

Seclion-builluo oirder

Fig. 4.133 Tspirnl fmming pian and built-up girders; First lnlcrnntionnl Building.

S e c t 4.41 Tubular Systems 265

Onter ie Cen te r Chicago, Illinois, USA .!,?i!: A'&hitect


Height from wee l to roof

Number of slories

Number oflevcls below ground

Building use

Frnme material Typical floor live load

Basic wind velocity Maximum lateral deflection


Design damping Emhquake loading

Typc of structure


Fooling type

Typical floor

Story height

Slab

Columns


Spacing

Material Core

Skidmore Owings and Merrill

Skidmorc Owings and Menill

1985

174 m (570 it)

57

I

Commercial, parking, offices, apartments

Reinforced concrete

2.5 kPa (50 psO

34 mlscc (75 mph) Hl500, 100-yr return period

Not available Not available

I to 1.5% serviceability

Not applicable Perimeter diagonally braced frames, flat- plate floors

27 m (90 it) of clay over hardpan 1.5-m (5-ft)-diameter caissons, belled to 3.6 m (12 ft)

Apartments 2.62 m (8 ft 7 in.) 178-mm (7-in.) flat plate, spanning 6.1 by 6.7 m (20 by 22 ft)

483 by 533 mm (19 by 21 in.) 1.68 m (5 ft 6 in.) at perimeter

49-MPa (7000-psi) reinforced concrete Not applicable

Onterie Center is n mixed-use 58-slory building near the Lake Michigan shoreline in downtown Chicago (Fig. 4.134). The building has a total area of 85.000 m' (920.000 it'), which is divided into five distinct areas by function. On the ground floor is lhc main public lobby and 1860 m' (20.000 ft') of commercial space. The single-level basement and the four floors above the lobby are a parking garage. Floors 6 to 10, at the tapering base, provide ofiice space grouped around two interior atriums. The sky lobby at level 2 includcr a health club, swimming pool, hospitality room, and mechanical equipment space. The remaining floors 12 to 58 consist of593 one-, two., and thrcc-bedroom aparl- ments (Fig. 4.135).

Because mixed-usc buildings need flexibility of core layout and column spacing, it was desiiable lo utilize only the exterior frame for thc resisiancc of lateral loads. In ihe


Fig. 4.134 Onterie C~ntcr, Chicago, lilinuis.

t, y , Sect. 4.41 Tubular Systems 267 3 ' Onterie Center tower all of the lateral forces are resisted by closely spaced reinforced i-

concrete exterior columns and spandrel beams. Additional lateral stiffness and struc- ), tural efficiency were achieved by infilling window spaces with concrete in a diagonal j pattern. These panels act not only as diagonal braces but a shear panels as well.

The diagonal effect of the shear panels tends to even out the gravity load on the ;' columns and also to reduce shear lag in the tube frame under wind loading. The entire ; lateral load is thus resisted by two diagonally braced channels, located one at each end

of the tower structure. Interior columns carry gravity loads only. The absence of a lateral load resisting core wall system allows a maximum of flexibility in planning interior space and eliminates the problem ofdiifercndal axial shortening.

Threc-dimensional computer modcling was used to analyze both gravity and wind load cases.

Pcrimctcr columns arc 480 by 510 mm (19 by 20 in.) at 1.68-m (5-ft 6-in.) centers. The510-mm (20-in.)-thick infill panels contain diagonal reinforcing bars as well as horizontal and vcrtical bars. The concrete strength for the exarior frames and interior columns varies from 52 to 28 MPa (7500 to 4000 psi). The floors me flat slabs with thicknesses of 178 mm (7 in.) for apanmcnts and 216 mm (8.5 in.) for commercial floors, using 35-MPa (5000-psi) concrete. Interior columns are spaced at 6.71-111 (22-it) centers. The external structural mcmhcrs are insulated lo minimize differential-temper- alurc indurud dcfonnations bctu,cen purimctrr and inlcrnsl culumns.

The d~3gon;ll shear panels used in the Otllcnc Center pruducc 2 high I c \ d ofstrac- tural efficiincv and create a distinctive architectural appearance. A similar systcm has been used on 780 Third Avenue. New York (see Fig. i . i37) .

Fig. 4.135 Typieol pion, 13th to 57111 noor: Ontcrie Center.


floor (the first of the residential floors) and the larcest office floor at the bottom. The tn- . p:r ir.:,, c\tendcd upr ;,rd until J I I ofthr. dc\clupcr's requircrn:ntr u.L.rc mL.1. The ~spcrcd fnrni .~lloa?d it c o r i l i ~ ~ u o ~ s SINC~UTL. In bc U I U ~ nn lhe iilc:~dc I11 create 3 tapcrcd I U ~ C .

'Tllr. ,lnr~.turnl r!ilcrn consi~ls u i cnlumnb and spandrel bu:,ms ;tad diacal~nl cross bracing, all acting together to form an exterior tube. The requirements of th; diagonals imposed a very rigid geometric discipline on the building. The diagonals from each face had to intersect at a common point on the comers so that wind shear, carried as axial loads in the web side diagonals, could be trnnsfcrred directly to the flange side diago- nnls. The diagonal X bracing is continuous from face to face and is connected to the columns, allowing load lo be transferred from bmcing to columns and vice versa. The beams are provided at the levels where diagonals intersect corner columns so that the diagonals could redistribute the gravity load among the columns. The gravity load in the diogonals causes them to always be in compression under wind loud, leading to much simplified connections. The redirtribution of gravity load also allowed all columns on each face to be made equal in size.

A typical tier of the tube consists of a primary systcm comprising columns, diagonals, and spandrel beam ties at levels whcrc the diagonals intersect columns at a noor level, and a secondary syslem comprisin~ the spandrel beams at other levels. The nri- ~. . - ~ - . ~~

m:ir!' ctruclurc \ \a1 r~ .qu~rcd 10 dc\ ,~. lnp conunuity 3nd to tmos,nit ari:,l l o~ds . Thc 131-

t r h l load is rcsislcJ ROC> hy c:~ntil~.iur aslion ano ?OF b) f r~rnc xlion. 'fl~is is duc 10 111s diayol~'lls c~calit)E :In almu\t onifur~n colutnn lo;d dirtribu~iun :lurus5 tllc flancc - face: thcre is \,cry little shcar lag. Thc struclural cfficicncy is demonstrated by a steel weight of only 1-15 kglm' (29.7 ps0.

The floors are a composite systcm of stcel bcams and a 127-mm (5-in.) semilight- weight slab. On aportmcnt levels the bcams arc arranged in such a way that lhey align with partitions and thcsoiiil oftlieslab is plastered and used as the finished ceiling. The geometric discipline of the extcrior diagonal module is maintained by three typical office story heights equaling four typical apartment story heights.

To achieve simple joints, the columns, diagonals, and ties are all fabricated I sec- lions. The thickest plate is 152 mm (6 in.) and the largest column is 915 by 915 mm (36 by 36 in.). Interior columns were designed for gnvity load only, using rolled and built- up sections. A36 steel was used for nearly all members.

Joints consist of double gusset plates to which diagonal members are connected by grade A490 bolts. Spandrel ties are field-welded to columns above and below, similar to typical column splices with bolted webs and partial-penetration flange rvclds. All gusset plate assemblies were shop-welded with comer gusset plate assemblies requiring stress relief.

The simple derailing resulted in an crection rate of thrce floors per ureck.

Sect. 4.41

780 Third Avenue New York, N.Y.. USA

Architect Swctural engineer

Year of completion Height from street to roof


Building use Fromc material Typical floor live load

Wind lood

Maximum lnleml deflection


Design accelenlion

Dceign damping Earthquake loading


Foodng type Typical floor

Story height Spandrel benms

Slab

Material

Columns

Core

Tubular Systems

Skidmore Owings and Merrill Roben Rosenwnsser Associates

1983 174 m (570 ft)

50

L

office Concrete

2.5 kPa (50 psfl New York City code. 1 to 1.5 kPa (70 LO

30 psO 180 mm (7 in.) at design load

4.8 sec E-W: 2 sec N-S 12 mg peak. IO-yr return period

I 4a serviceability; 2% ultimate

Not applicable Diagonally braced cxterior tube

~ o c k . 4 - ~ ~ a (40-ton/ft2) capacity

Spread iootings

3.5 m (I1 ft 6 in.)

380 mm (15 in.) deep 380-mm (15-in.)-deep one-way joist and two-way waffle slab Concrete. 31 and 28 MPa (4500 and 4000 psi) 1220 by 610 mm (48 by 24 in.) at ground noor Concrete, 41. 34. 28 MPa (6000. 5000, 4000 psi) Concrete walls and columns: concrete strength ns columns

The trend toward very high-rise construction in concrete has received a big boost due to the adaptation of the first diagonally braced tube system to concrete swclures. The fifst of its kind is the 50-story office building located at 780 Third Avenue, fiew York ( F I ~ 4,137). which was completed in March, 1983. Its very slender aspect ratto of over 8:l IS

what suited it to this design approach. The building contains ~ l 0 s e to 46,500 m2 (500,000 it') of office space. Its struclural

system is a hybrid, utilizing thrce varied systems-a truss, a tube, and, to a minor extent, frame and sheor wall interaction of its remaining structural componenls. All SYS-


[ems interact to provide gravity and latenl load-carrying capacity at an efficiency not previously available. This hybrid system appears to rcmove any practical heigllt limit from design in reinforced concrete (Fig. 4.138).

The "concrete tube" consists of closely spaced perimeter columns which are connected at each floor level by spandrel beams. In addition, thc tube is braccd by a diagonal pattern of rectangular panels, in place of window openings, betwecn adjacent columns and girders.

--

Fig. 4.137 780 Tllird Avcnuc, Kwr Tsrli. (Coi8rtc.r~ r?rRnbm Rorm,>mrrer~s .~ .roc)


The building is 38 by 21 m (125 by 70 ft) in plan, with an overall height of 174 m (570 ft), consist~ng ofa4.4-m (14.5-ft)-high first story and48 3.5-m (11.5-ft)-high standard stories. Perimeter columns are 1.2 m (4 ft) wide, with window openings 1.6 m (5.3 ft) wide. The column h i c h e s s reduces From 610 to 457 to 406 to 356 mm (24 to 18 lo i d t i 14 in.) a floors 2.20. and 32.

The spandrel beams, which arc the solid edges of the floor construction and are flush bottom with the one-way and two-way joists. are 380 mm (15 in.) deep by 1 m (39 in.) wide, except for those at the second floor. which are 762 mm (30 in.) deep by 610 mm 174 in I wide .- . ----, -~

'The concrete bracing panels arc of the same thicl;ness nr the ndjncent columns 2nd are placsd integr~lly ui th thc~ti. The purpose of adding bracing to the lube is lo reduce illear log cffccts. and hence improvc the pcrfurmnncc of the struclurc for bnth gravity and wind loading. Thc wide iscer of thc huilding h a w double diagonol bmcinp. whc re~s thu nmoa iaccs hnvc only singlc diqonal bncinz in a rlgz;iy p;lltcrn.

'lhc concrsts rtrcngth of the columns and p:tncls varies 310110 IIIC huilding hcight. Thc maximum slrenath of 41 hlPa (6000 mi) is rcduccd lo 35 hlPa (5000 psi) in the - ~ ~ -

middle third and to 1 8 MPa (4000 psi) in'& top third of the swcturc. ~ h e concrete strength of the floor members matched 31 MPa (4500 psi) with 41-MPa (6000-psi) columns and 28 MPa (4000 psi) with the lesser-strength columns.

Another structural element in the building is thc set of elevator core walls. Because oithcir small size and central location they are considered to be of secondary impar- lance in their influence on the braced tube's behavior.

The wind pressure applied to the building is in accordance with the New York City building code, increasing with lmight in steps up to a maximum of 1.44 Wa (30 psO at thc 91.4-111 (300-ft) levcl and above. The results o f a wind tunnel aeroelastic test verified that thc code's wind-pressure requirements for the design of the structure frame

Fig. 4.138 Typicul l r n m i n ~ pin": 780 Third Arcnur.


were not exceeded. The cladding design requirements were, however, upgraded on the basis of the wind tunnel test results. The projected 10-yew return maximum acccleralions of 12 mg registered well within the occepled industry limits for office structurcs.

Results from Be analyses performed for 780 Third Avenue that are of particular interest are those that indicate increased cracking and reduction in the effects of shear lag by the bracing on the column forces of an unbrnced tube structure.

Results of sensitivity studies and the influence of the panels on lateral sdffness are illusmated by the deflection curves in Fig. 4.139. Evidently cmcking in floor members is very detrimental to the stiffness of unbraced tube structures (curvcs I and 11). but of only secondary importance in braced tubes (curves 111 and IV). The stiffening effect of the brncing is demonsvnted both in the reduced sway and in the modified-mode shape of the deflection curve (curve I versus curve Ill). The unbmced lube deflccts in a wall- frame configuration, with concnvity downwind in the lower pan, concavity upwind in the upper part, and a point of contraflexure at about two-thirds of the height. The braced tube deflects in a more strongly flexural shape with a much higher point of contraflexure. The component of Lhe mbe's deflection due to racking shear of the columns and

HORIZONTAL DEFLECTION (fl)

IV BRACED TUBE-UNCRACKED RFAMS - -- -- - 111 - - - - - BRACED TUBE--CRACKED BEAMS I I TUBE ONLY-UNCRACKED BEAMS (1.1

Fig. 4.139 Dclleclionr olrlructurc.


spandrels was, lherefore, reduced significantly by the bracing. This is further supported bv the small increasein the overall deflection when the spandrel stiffncsses are asigned t i e large (50%) reduction to account for cracking.

.

The deflection curve for the braced suucture with cracked bcams shows an increase in drift of 4% at the top, and a minimum increase of approximately 7% at about midheight. The maximum drift per story, however, which occurs in the middle region of the building, was hardly affected.

The small influence on the overall lateral stiffness of the braced structure of a 50% va~iation in the moment of inenia of ihc spandrel beams indicates that their flexural stiffness, and therefore their depth, in the braced tube strucmre are of secondary importance. Their primary rolc is to nct as ties or struts in developing the axial forces in the intermediate columns.

Figure 4.140 indicates ihc placement of the panel reinforcing. The column and spandrel bcam reinforcing was extended through the panel, which was also reinforced with lieht orthoronal reinforcements to minimize ihc size of accidental cracks. Collector re-

L

inforcing. suppicmunliog litc rpandrcl rcinforccmcnts, war added to i i~c lop and buttom of the panel tu ;lugmcnt the lcnrile ruquiir.munts at the intcr,uctions Splicer an the m ~ i n rw~odrel rcinforu:mcsts aerc slaggurtd tu providc for lcnsilc forccr in the .p:!n~lrcl - -

beams. The construction of the concrete structure, from first footing to roof level, took 13

months to complctc. Thc building required 16.000 m' (21.000 yd') of concrete and 21 SO tonncs (2400 tons) of reinforcing bars. A 3-day construction cycle was easily main- taincd for the typical floors (a Zday cycle would have been possiblc with ovcrtimc).

Direction ol force in diagonals

Spandrel reinfc. Collector reinfc. Column reinfc. Diagonal reinfc. Collector reinfc.

Spandrel reinfc.

Fig. 4.140 Urucing punel rcinfureirlg luseul.


Hotel de las Artes Barcelona. Spain

Architect

Structural engineer

Year of complclion

Height from street lo roof Number of stories


Building use

Frame material Typical noor live load

Basic wind vclocily Maximum lateral dcflcction

Design fundemcntal period Design acceleration

Design dantping

Earthquake lo~ding

Type of structure

Foundation condilions Footing type

Typical noor

Story height Bcam span

Bcom depth Beam spocing

hlateri;~l

Slab

Colun~ns Sizc st ground floor Spacing hlolcriol

Corc

Skidmore Owingr and Merrill

Skidmore Owings and Merrill 1992

137 m (450 fi) 43 1 Hotel

Structural steel

2.87 kPa (60 psD 40 m/sec (90 mph) at 30 m (98 St)

H/50O, 50-yr return period 5.2 scc

Not applicnblc

I % sensiccobility

No1 applicable

Diagonally braced lube in tllc form of mefa portal frames Dense sand

Aufcred straighl sltnft piles construc~ed undcr bcntonitc slurry

3.00 m (9 it I0 in.) Office 9.2 m (30 St)

Orlice 157 mm (I8 in.) Office 4.6 m (15 ft)

Sleel. A572, grade 50

75-mm composite metal deck + 60-mm 12.4-in.) concrete + 55-mm (2.1 in.) scc- and-pour concrctc

W350 by500 1bIf1 inlerior: \\TA4 21 eh l ek r 9.2. 13.8 m (30. 45 St) A572 grddc 50 Braced lo p a n belr.cen mega brncing pencl points; rlcel-braced rrilrnes in orthogonal directions

The Motel dc las ilrtcs tower is the ,must prominent par1 of n multiusc cornplcx in Barcelona. Spain. consislinf o i 5-slur luxury huteliapartment units. commercial oiiics space. retail. porkin.. and beallll club f:~cililics (Figs. 4.141 and 4.142). Thc project is

Tubular Systems 277 Sect 4.41


luc3tcd along Barcelona harbor, overlooking the hlcditcrranetln Sea, and uas colnpielcd in time for the 1992 So~ltmer Olgmpic G m e r The Hole1 d r 13s Ancr i.; o:tn of:$" n,.p,. - - -. . -. - . . - . - . all plan to provide new infrastructure and private development of individual building parcels in the Olympic Village area. The lower is envisioned as one of the focal points in the reawakening of Barcelona as a major European capital.

Fig. 4.142 Frurnvsurli: Holcl dc lur Art-.


Continuing a long tradition at Skidmore Owings and Memll. thc uchiteclural form. crnression. and aniculalion of the tower a 2 all bascd on thc beauty and esrccnce of the expused, pninled stmclurol stecl fume. The archi~ecturnlly exposed X-braced framer located on the building periphery nrr organized on a Cslory [I?-m (39-R)] module. These frames form a fully three-dimenrianol iystern resisling nll wind and seismic 1atcr.xl forces nr well as abortion of the tower siavitv load. o st he Full building inertia is uti- . ~ . - ~ ~ - - . lized, n very eifici'ent lalcnl load resisting system is obmincd, with very lillle stecl ueight abort that requircd lo resist the toucr gravity load.

From thr: archileclural point of view. a clear articulationof the cxtcrior slmclurc was desired. which is charactcnzed by the crisr, aro~ortions of steel I beam, columns, and hilf-an members. as well as the honest exbressfon of thc connectins ioints. both bolted .,. ~-~ . -. 2nd ucldr.d.The cxtenor cunnin wail is set back 1.5 m (5 It) from the pcrimrler. thereby nrovidins n c l eu architsctural expression of the exposed X-braced slcrl frame. An open. ; e b l i k e ; ~ c ~ r e allowing the play of daylight through the frame, much desired by the architcctural design team; was-bainncedbythe need for robusmess and slructurnl integrity, particularly at the memberjoinls. Exterior frame members were chosen on the basis of erectabilily, connection detailing, nccessibility for slcel painting and future maintenance, and visual considerations related to the architectural aesthetic.

The issues of corrosion and fire protection were addressed in engineering the exterior exposed steel fmme. Corrosion protection for the exposed steel members is providcd by a durable fluorocarbon paint system designed for long life under the coastal marine environment, consisting of a shop-applied primer, undercoat, and finish coat. with a sccond finish cont applied in the field after erection of the stecl frame. The non- fireproofed exterior structure was anolyzed using the latest slate-of-the-art fire engineering mcthods developed in Europe and the United States. Analytical methods to determine the steel lempcrnturcs as well as the charncler and nature of n number of hypothetical design fire events were stndied. High-tempernNre structural analysis of the entire huildine frame comaleted the fire eneineerins desipn.

~ - - - A simple, straightforu,nrd architcctural cornpoiition expressing thc inhercnt function

of the Slruclural frame, thl: Hole1 de Ins Ancs loner represents n prominent !\or), com- hinine architccmre and ,uuctur~l rngincuring, marking a major intcm3Uonnl cclubra- tion in Barcelona during the summerbf 1992.


PROJECT DESCRIPTIONS, BUNDLED TUBES

Sears Tower Chicago, Illinois, USA

Architect Skidmorc Owings and Merrill

Structural engineer Skidmorc Owings and Mcrrill Year of complelion 1974

Height from street lo roof 443 m (1451 it)

Number of stories l I0 Number of levels below ground 3 Building use Omce

Frame material Structural steel

Typical floor live load 2.5 Wa (50 p s0 Basic wind velocity 34 mlscc (75 mph) Maximum lateral deflection H1550. 100-yr relurn period Design fundamcnlal period 7.8 scc

Design accclcration 20 mg peak. 10-yr relurn pcriod Design damping 1.25% scrviceabilily

Earthquokc loading Not applicsble

Type of structure Bundled framed lubes Foundation conditions 18-m (20-it)-deep steel-lined concrcie

caissons Footing type Roft Typical floor

Story height 3.92 m (12 fl 10.5 in.) Truss span 22.9 m (75 fi) Truss dcplh 1016 m n ~ (10 in.) Truss spacing 4.6 m (15 ft) Material Steel, grade 250 MPa (36 ksi) Slab 63-mm (2.5-in.) lightweight concrete on

76-mm (3-in.) metal deck Columns

Size at ground floor 990 by 610 mm (39 by 24 in.) built up Spacing 4.6 m (15 it) Material Steel, grade 350 MPa (50 ksi)

Core Not applicable

The Sears Torvcr is the world's lellcsl office building with a height o f443 m (1454 it) above ground (Fig. 4.143). It conloins 362,000 m' (3.9 million it') of oflice space in 109 slorics.

The setbacks in tile facade result from reducing floor areas required by tenancy considerations. Sears. Roebuck and Company required large floors for their opcrotions, whereas smaller floors were best for rcnlal purposes. The adopted bundled tube concepl

282 ' Latsral Load Resisting Systems [Chap. 4

provided nn organization of modular areas which could hc terminated at various levels to create floors of different shapes and sizes (Fig. 4.144). Each tube is 22.9 m (75 ft) square, and nine such tuhes make up n typical lower floor for an overall floor dimension of 68.6 m (225 ft). This square plan shape extends to the fiftieth floor, where the first tube terminnlions occur. Other terminations occur a1 floors 66 and 90, creating floor areas of 3800 to 1100 m'(41.000 to 12.000 ft21.

The structurr: acts as; venicni canlilc\,er Lxcd at the hase lo resist wind loads. Nind square rubes of varying heights ;Ire bundled together lo crcale ihr larger ovcnll tube. Ench tubr comprises columns at 4.58-m (15-11) centers connected by stiif bcnms. Two adjacent tuhes share one sel of columns and henms. All column-to-he& connections are fullv welded. At three levels. the lubes incornorate trusses. orovided to m&e the axial . . ~- ~~~~~~~~ ~~~-

column loads more uniform where tuhe.drop-offs occur. Thesc trusser occur hclow floors 66 and 90 and between floors 29 and 31.

The two inarior frames connect opposing facade frames at two intermediate points, therehv reducing the shear Ian effect in the flanee frames. This reduces the oremium for hcigbt~onsidcr;~bly as shoun by the relnli\ely-lou unit stmctur;il rtccl qu;oli~g of 161 Lglrn' (33 pro. The uind-induced sway is nbout 7.6 mm (0.3 in.) per atory, and tltc fundamental period is 7.8 sec.

The 22.9-m (75-ftl-square floor arcos of each tube are framed hv one-wav trusses spanning 22.9 m (75 ft) i t 4.58-m (15-ft) ccntcrs. Each truss conneci dircctly'to a column with a high-strength friction-grip bolted shear connection. The span direction o r these 1NSScs was alternated every six stories to equalize gravity loading on the columns. The tmsscs are I020 mm (40 in.) deep and utilize all of the available depth in the space between the ceiling and the floor slab above. The spaces between the diagonal truss wch members allow the passage of up to 530-mm (21-in.)-diameter air-conditioning ducts.

Benms and columns are built-up I sections of 1070- and 990-mm ( 4 2 and 39-in.) depth, respectively. Column flanges vnry from 609 by 102 mm (24 by 4 in.) at the hot- tom to 305 hv 19 mm (12 hv 2.75 in.) at the too. and henm flanres from 406 bv 70 mm (16 by 2.75 k.) to 254 by Li5 mm (10 by 1 in.j. A total of 69.000 tdnnes (76.ion tons) of structural steel was used in the project, consisting of grades A588, A572, and A36.

The steel-tube structure was shop-fabricated into units of two-story-high columns and half-span heams each side. tvoicallv weiehine 14 lonnes 115 tons). The shoo fahri- .. . - cation climinatrd95560f field uelding. ~u toma t rd r l r c l ro s l a~ weldini was usedior thc hull aulds of hcnms to columns. The continuity plates ocrors columns at the joints ~ c r c fillet-welded by the innershield process.

Because site storaee sonce wns unavailable. the frame units were delivered exnctlv when needed and lift&! oif the truck into place. Except for column splices, all field con'- neclions were grnde A490 high-slrength friction-grip bolts in shear connections. Exte- rior columns were insulated to limit the average temperature differential between these columns nnd interior columns.

Sect . 4.41 Tubular Systems 283

. . r b "7

N N 3' cellular deck I1

21/2" It. wt. cond D 'ul r-

z

Typical lraming plan (levels 1 lo 50)

(a)

Modular lloor conliguralion

(bl Etg. 4.144 ScorJ Tower.


Shear lag behavior

F ~ R . 4.144 Srnrs l'cmrr. ~ C ~ ~ n r i r , , , ~ d ]

Sect. 4.41

Rialto Building Mdbourne, Australia

>,.'., Architect

..... .. . , . . Structural engineer

Ycar of compiction Hcight from sUcel to roof

Number of storles

Number of levels below €101

Building use Frame nlatcrial ~ y ~ i c a l floor live load

Basic wind velocity Maximum lateral deflection Design fundamental pcriod


Type of strucmrc


Fooling type

Typical floor


Beam depth

Bcam spdcjng

Slab . :-,, g; ?t :

Columns ,?I;

,.*a Size at ground floor

2. ..?. Spacing r t : , z s!. htaterial .< ,.,: L. "~:

Core .-

Tubular Systems

~ e m r d de PrcuPenott Lyon Mathieson Pty. Ltd. Meinhardt Australia Ply. Ltd.

1985 243 m (797 fi) 63

2 Office Concrete

4 W a (80 psfl 39 mlsec (87 mph). 50-yr return 230 mm (9 in.). 50-yr return

6.1 scc 3% serviceability: 510 ultimate

Not applicable concrete core with concrete perimeter frames ~ a s a l t over sands and clays over mudstone Caissons 1500 or 1800 mm (5 or 6 ft) in diameter. 18 m (59 ft) long, socketed inlo rock

3.9 m (12 f 9 . 5 in.) 10.5 m (34 ft 6 in.)

500 mm (20 in.)

5 m (16 ft 5 in.) 120.mm (4.75-in.) lightweight concrete

1.2 m (4 ft) octagonal

5 m (16 f t 5 in.) Concrete. 60 MPa (8500 psi) Shcar walls. 750 mm (30 in.) maximum thick at ground floor

hlatcrial Concrete. 60 MPa (8500 psi)

A number of structural systems for the Rialto Building (Fig. 4.145) were initially in- vestigatcd and a reinforced concrete swctural system was finally adopted, with speed of construction being a prime consideration in the dcvclopment of formu,ark and reinforcement dctails

,>: .2,: I ;..


Fig. 1.115 Riulto Building, hlrlbuurnc, Austmliu,


The external frame or coluntns and beams, urhile being designed for the direct dead and l ive loads aoolicable. acts as an external tube i n resirtine lateral load. Althoueh the . . - plan shap: i r uns)t~t~aetricaI 3ad tltc colutons arc 5 m (16.4 i t ) apart. ;lnaly$is 01 lhu i n ~ d tmnsfer ardund the uurners indicated re>runxblc thrce-din1:nsiunal action. l h l : corner beams connecting the end columns are most oecessary for Lhis action. The tube effect also provides forsome latcrnl distribution of load from thc more heavily loadcd columns (Fig. 4.146).

Thc service cores, being the major elements i n the structure, were the subject o f a number o f detailed considerationr. No sizable penerrations or rebates were permitted in the main walls. Sizine ofthe walls was not oolv for Iondine considerations. but !v\'as the suhjcct ofrhrinkngc 2nd 2rr.r.p ust i~nat iun~ 2nd r~.fiocmcnt for buildlng pcrfornlsncr.. F i - n d checking af thc intcrnctillc corcl rind r.\tr.rn;jl frames u.2~ cxr ied out using n tl>r~.i.. dimcnrionxl l in i tu -~ I~ . , l~snt on:~l)sis.

Design u inJ 102ds in th? b.ulding wcrc calculated ~ ~ i n g mctcorological d313 3s13il- z~hlc. Thc hui l~l ing ir of S L C ~ 3 beigttt, r i le. 2nd s l e e d ~ r ~ ~ ~ a s that ths diifr.rcnt :~ppru~ch tclocitiu* 2nd wind dcrcctiurl, nurr qignilicant ~n the dci ig~t. \ \ ' i d tunncl tsats dutr.r- mlncd design prcssurds 10, hoth the iruilding ;and the facade. Frntn thc north, elst. and rvrrt. terrain category 4 (1.36 applicable. ~ l t i l c [ram th~. south, with Port Phillip R3g be- in^ 3 km (?, mi) distnnt. tcrrain~cnteeorv I was considered above level 30 . ~ - .

Tlic i;,icr>l projcctirm of thc h ~ ~ l d i n g , being s.ynmctric31. inducer 3 $rind fnrcc un thc s t r~c l t ! r~ t h ~ t n.ll >luj!s cnnfc,rrn a1111 lhs c ~ n l e r uf J t i f in~sr . Ti16 pr ,r1111dlr.r bcnms and cores have bccn modilied to align thc ta,o centroids as closely as possible at all lcvels: homevcr, a section of tllc building between levels 24 and 40 is subject to a twisting force. Thc calculnted drift at the top of the tower undcr maximum design wind forces and incorporatina this twisting i s 230 m m (9 in.).

A major consideration addressed and rcrolved early in the design phase was the aspect o f shrinksge and creep o f lhc concrete structure. Most buildings of [his size r\,orld- u,ide are steel framed and not subicct to these tvocs of mo\~emeots. , ,

.An nsaussmeol i,i 111~1 C I ~ :xnd shritlkagl: UI VL.~ICII ulemcnls in llic prujecl $$as c:lr- r i ~ d out i ~ r ~ h i n g use uf rurcar:lt dht3 i l v ~ i l b l ~ tcurnlhe United Sri l le~. USL~~LLI?~~:C \;$I- ucs derived for material properties and predictions wilh regard to weather and building orouram. a comouter oroeram was deselooed taking into account member size. concrete . . = . = str~.ttgth, r:inforcr.m~.nt ratio, age ;I 1o:iding. I~umidtty, loldittg condit~uns. and cre:p and sIirink3g~. d~velopm~.nt. I t N ~ S anticip:~tr.d th;it thc total nonelartic .~hon~.nisg oi the 65- storv to& would be on order of 1% to 200 mm (6 to 8 in.). Provided allowances are ~itsde in tlte atlachntest of non-ln~d-bu3rinb ciements such its l ~ f t r ~ i l s atid the faode, the magnitude u f l h i r nnnvlastic dsform;~tiott is ttot i ign~ i lc in t . HU\I~\L.I, cliff~r~.nccs in tltc msni lude uf ihnnkage ;md crsup inirltirt :1 1x11 concrete structure 15 3 ntajur .ulljcct n f concern, and this is p&ticularly rclc~,ant in the case o f the Rialto towers.

Lone-term differential shortenine bcr~veen the central core and nerimelcr columns at - - the top of a typical tower building can be readily catered for as the distances between thcsc elements are usually large. Thc combined shrinkage and creep lo be expected after construclion of the upper levels o f the Rialto lO\\.er5 indicntcd differential rnlucs of 10mm (% in.) in thecase o f towerB and 11 m m (% in.) in thecascofto\verA.Thc min- . .. . . . . i m ~ n l sp:~ns i n ~ n l ~ ~ ~ d l r c 9.7 01 (32 11) 2nd 7.0 in (23 it), r-sp:cli\ely. I-lot\c\r.r. o * tun - d r i \ 2nd B furm a n intugr~tr.d itruclurc. 3 differr.nti:~l \ i~lul: un the urdcr of 38 inn1 (1.5 in.) could he -.\PL.CIC~ bct~ee11 >di;lc~.nl c ~ l u t ~ l n r ill I~.!el -41 ( IoNL.~ B rnnfj ~ U L . 10 effects o f the addiiional I 7 levels o f k w e r A. The distance between these columns is only .I 111 (13 ft). ;~nd clcnrlg ru;h inotcntcnt, u:tn~tut hu tolr.r3tsd in a ~ o n s t c ~ ~ c t i ~ n u i t t l i r !la- lore. Jointing of l l tc t u ~ c r s e l r not 3ccepli~hlc. 2nd tlte ~rovisiort nfi!.'h:lt"xt this l e \ ~ 1 was unsuitnblc to Lhe architecture, as !,,ell as inducing a long-term out-of-plumb ofthe top o f tower A.


Fig. 4.146 Fluor pions; Riallo Uuilding


The solulion arriied at uas to "play a cunfidcnce lnck" on lo!rer 5, nlabng lhe structure '.bcliwc" it is 17 slorics Inllur. Prcrtrcrsing cohles are provided from lcvel I to level 38 and stage stressed as tower A conslrucdonproceeds. Thereby nll columns below level 38 are subject to the same loadings at the same time, and therefore elastic and nonelnstic shortening values are relatively consistent for the lifetime of Ule building (Fig. 4.147).

Fig. 4.147 SLnged slresring; Rlnlla Building.


N6E Building Shinjuku-Ku, Tokyo, Japan

Architect Nihnn Sekkei Inc.

Strucmnl engineer Nihon Sekkci Inc. Year of completion 1996 Height from street to roof 189.6 m (622 it) Number o r stories 46


Building use Offices and retail Frame material Stccl Typical floor live load 5 kPa (100 psn Basic wind velocily 35 mlsec (78 mph) hlavimum lateral deflection HtZOO. IOO-yr rctum Design fundamental period 4.56.4.75 scc

Design acceleration 35 mg pcak. 100-yr rcturn

Design damping 1% rcrviceability; ?% uldrnate Eanhrluakc lr~ading c = 0.0533

Type or structure Dundlcd tube Foundation conditions Clay and rand o\,eigravrl Typical floor

Story height 3.95 n~ 113 ft) Beam span 19.6. 16.4 m (6-1 f t 1 in.. 53 it 10 in.) Beam depth 800. 600 mm 131.5.23.5 in.) Beam spacing 3.2. 3.6 m (10 fi 6 in.. I I it I0 in.) Slab 135-mm (5.15-in.) reinforced concrcte

Columns

Size at ground level 600 by 600 mm (24 by 24 in.) Spacing 3.z.3.6 m ( I 0 Cl 6 in.. I I It 10 in.)

Core Fremcd tube

The plan dimensions of the N6E Building ore 92 by 39.2 m (302 by 128 it), which is quite large (Fig. 4.148). The core location caused eccentricities that could not be rcduced using shcar \raalls or bracing systems, so the bundled tube r).stcm was adopted to ochicve a symmetric structure and lo avoid torsional problems (Fig. 4.1491. This mas done at the expense of reduced span lengths and incicased numbers ofcolumns.

The building response was estimated using ail available data as well as the along- wind and cross-wind power spectra end cospectra, which vary with the building heighL Ail cslculetions were donc forl: J. and lorsional directions.

Tubular Systems

Fig. 4.148 NGE Building, Tekyo, Jupnn.


Fig. 4.149 Typical structural plnn; N6E Building.

Sect. 4.41 Tubular Systems 293 I Carnegie Hall Tower New York, N.Y., USA

:.. . . . 2, : L

Structural engineer

Year of completion Height of street to roof Number of stories

Number of levels below ground Building use Frame material Typical floor live load Basic wind velocity Maximum lateral deflection Design fundamental period Design acceleration Design damping Earthquake loading Type of structure Foundalion conditions Footing type Typical floor

Story height Beam span and spacing Beam depth

Slab Columns

Material Core

C e s u Pelli and Associates (desim) Brennan. Beer, Goman Associates Robert Rosenwnsser Associntes 1989

230.7 m (757 ft) 62 I

Office Concrete 2.5 kPa (50 psf)

47 mlsec (105 mph). 100-yr rcmm period Approx Hl500. 100-yr return 4.8 sec E-W; 3 scc N-S: 2 sec torsion

20 mg peak. IO-yr remm period 1% serviceability: 2x7'0 ultimate Not applicable Side-by-side concrete tubes Rock. 4-MPa (40-tonlft') capacity Spread roolings

3.66111 (12 ft) Vnrying 457 mm (18 in.) interior; 762-mm (30-in.) spandrels One- and two-way, 230 mm (9 in.) thick

I Size and spacing vary Concrete. 58 MPn (8400 psi)

i !

S h e u walls ( p u t of tubes); thickness varies; concrete as for columns

At 230.7 m (757 11) in h?iphr. Camepie IJall Tosser ia the iccond 1:~llest concrcle rlruc- lure in N r u York Cily and thssighth tollssl in the wnrld ludly (Fig. 1.150). With a 15.2- nl (50-TI)-ulde ~nnnll Tdce and 1 2?.9-m (75-r1)-wide south race. which olfsc.1~ lu a 15.2- m (50-it) face above the forty-second floor, this 62-story SlNClUrc is the most slender habitable building of this height ever constructed (Fig. 4.151). The structure occupies the narrow site bctween the five-story Russian Ten Room and the 100-yeor-old Cornegie Music Hull. The structure's nrchitect. Cesar Pelli Associates, dictated the structural scheme by "sculpting" the structure to complement the existing music hall. The double (side-by-side) tube structural system that resulted rvss actually defined by filling in all the available spaces bctmeen the desired windows with concrete. This resulted in nonuniformity in column size and spacing.


Fig. 4.i5U Curneglc Holi Tower, KEIV Yolk.


The nonuniformity in the size o f the columns at a level was also extended venicolly as offseu and larecr or smaller window sizes dictated relocation or alteredcolumn sizes. -~ -~~~~ - -~

Often Viercndcel nction u,as nerdcd to terrninntc venical eletncnls at vlrious locations without the benefit of trnnlfer girders. This occurred on the nonh and south walls and above the fortv-second floor fir the south hal f of the west wall, which spans over the enlareed haze: Vicrendcel action was also reauired direcllv above lhe ihroueh-block - ~ - ~~ ~

p l r jags at the ground floor and at sevcral othcr localions. A center u r b (perforated by lobby egress requirements), common to ihc1u.o side-by-

side tubes. w m needed to heln Ule north- and soulh-wall columns to efficienllv connect the C ~ S I nDngc. wall to l c w&t flange wall with minimum shmr lag. A ~ lercndee l column (skipping alternate floors to minimize the lobby obstructions) u,as introduced to rc- ducc the clear span u f ihc center wcb. This Vicrcnducl column i s the only intcrior culumn i n the stru;ture. which othewisc s u o o o ~ dl rrnvitv loads bv thhexterior tube . . - - uolutttns and t h ~ . ~ . Ieva lnrcor~ wi!lls. The large c l x r spms o f 9.1 m (31 it) and more bc- 1,vccn the elevator core and tlic ucr t wall wcrc spanned wllh 230-mm (9-in.) slabs nnd shnlluu beams ,157 mm (18 in.) deep. This f r an l i n~ for gravity loads proved to be [nore economical than one-way ioisu; o rwaf f le slab coislruction bccausi i t orovided more mdss to rcsist uplift forct~s?roln wtnd loads and to reduce bullding acccl~rations. I t also pro\idcd c x t n height to accommodate mcchanic:,l systems so that with 3 lutal slog. height 013.66 m ( I ? it). 3 ceiltng height o f 2.7 m (9 i t ) uas maintained.

TIIS douhlc tuhc design relics hcavily on 760-mm (30-in)-deep spandrel beams to tnpage 211 tltc vcntcnl suppuns to rcsist thc rxind act io~i and to equalize the SI~L.SSCS due to gravity l o ~ d s in all suppons rugardlcss ofthcir smr. The tube's venical rttcmhers var- i t d bstr\,cen l R O and 2590 mm (19 and 102 in.) i n length (parallel lo tltc cxtcrior) and included a solid concrete wall behind the service core &a to the cast. The structural design cnnsidcrcd hoth the relasation duc to long-tcrm crccp and 5hrinkagc ofthe concrew mumbur, dnd the instnntaneous demands of the wind iurcer.

Ennugh gmvity loads % v ~ . r r . :lassmbled to clitninatc the possibility of tension duc to wind in the vertical supporn and to ict the gravitational loads anchor the structure. A few rock anchors at the west end o f thc center web were added to enhance the vbilitv o f < -~

the web l o cngspc llie flanges cv6.n under larger lateral loods than dicvatcd by the Nerr York City cndc or the wind tunnul ru,ults.

'lllc prelintinary design considered both steel and concrete. Conuol ofthe ourceotion . . of motion w i t h o u i a u x i l ~ m means such as damoers was found to be nttainableonlv with

~ ~ - - - - ~~ , --.. tit: concrete allerrtalivc because of ihs larger damping 2nd weight of a concrete stmc- lure. Hu~cvL.~ . 1S a prt~i lu l iun. because o f its extreme slendcmcss. the stlucturc was ds- signed to accommodate a pendulum-type damper. Field meaurements, after the structure was topped out, indicated that dcsign predictions were accurate and n damper was not needed. The anticipated accelerations, projected from these load mcnsurcments. should not exceed 20 mg for the 10-year return pcriod.

Concrete was pumped i n to the fu l l height o f the structure. Concrete strength i n the columns did not exceed 58 MPa (8400 psi) because the use of silica fume i n New York City was sti l l questionable at the time the structure was designed. For this and other slender structures, stiffness, weight. and damping are the important parameters diclat- ing the slructurc's behavior. The design for acceptable perception o f motion oRen ovcr- rides othcr more mundane design requirements such 3s strength and stability.This aruc- lure together with its earlier slender siblings (Metropolitan Tower. Cityspire, and the Concordia Hotel) ore prototypes of the future mcgastructures of the neat generation o f I d 1 SLIUCLUres.

Sect. 4.41

Allied Bank Plaza Houston, Texas, USA

Architect . Y.*::.:,h

Stru=tuml engineer

Year o f completion

Height from sueet to roof

Number of stories

Number o f levels below ground

Building use

Frame material

Typical floor l ive load

Basic wind velocity



Design acceleration

Design damping

Earthquake loading

Type o i structure


Footing type

Typical noor

Story height

Beam span

Bcam depth

Beam spacing

Material

Slab

Columns

Spacing

Material

Tubular Systems 297

Skidmore Owings and Mcrr i l l

Skidmore Owings and M e m l l

1983

296 m (972 it)

71

4

OlEce

Stmctural steel

2.5 W a (50 psO

Unavailable [force = 196 kNlm (13,400 Iblft) for 100-yr rclurnl

H/500. 100-yr return

Not available

Not available

I % serviccnbility

Not applicable

Pcrimeter framed tube; diagonally braced core with outrigger trusses

Stiff clay

Mat 2.9 m (9 f t 6 in.) thick

4.0 m (13 i t 1 in.)

15.2 m (50 ft)

530 mm (21 in.)

4.6 m (15 it)

Steel, grade 250 MPn (36 ksi)

83-mm (3.25-in.) concrete on 76-mm (3- in.) metal deck

Built-up. 1016- by 610-mm (40- by 2 6 in.) pcrimctcr: 610- by 610-mm (24- by 24-in.) interior

4.6-m (15-ft) perimeter: 9.15- by 6.1-m (30- by 20-it) intcrior

Steel, grade 250 and 350 MPa (36 nnd 50 ksi)

'i. 1 : core Braced steel frame, gradc350 MPa (50 h i ) ~- :~. .%.

3.22 h All ied Bank Plazn was designed to relate strongly to the buildinps around it. Situated on :I<

?:! a site which is essentially the center oldowntown Houston, the building has a major tm-

,:2. pact on the western iacadc ofthe city; which is the most dominant view of its skylinc. :$ .*., In form and mnterials, a design was sought which would be distinctive but would Scr\pC 4: ;?2 ~:&: &?. * P ~


to complement and tie together its surroundings. A form that tnovcd and flowed was felt to be nppropriatc, one that wns sort and sheer rather tltan 1t;lrd and opaque like the granite and steel rectnnnulnr buildines around it (Fie. 4.1521. - - -

The resulting semicurved lower was uchievcd by juxtaposing two quarter-cylindcr shafis (Fig. 4.153). The 71-story tower is sheathed in dttrk green rcflccdve glass, chosen for its sheer quality and rcsponsivencss to light. Tite combination orp lans and curves in the building's design will allow a cconrtant intcrplay of sunlight un its surface.

Fig. 4.151 hliird Unnli I'inzn. Hoartun, Tcsits. tPbrlio I? HedN'rS-Blcrriag.1


Givine the buildine a human scale was another imoonant asoect or the desianer's in- " b

tcnlions. Unlike many recent buildings, which are sheathed i n reflective glass and appear only as a huge mass. the swcture of the Allied Bank Plaza is subtly cxprcssed with venical&d horizonml mullions. A formal ooml on theeastsideoflhe b$ldi"eorovides asense -. of cnlr).. Slncc h5rc or the public u n e r r the tun~~el-cotittccted dounloun buildings st the underground lcrel. Allied Bank PICA o l r ~ r s t l i ~ olily entnnce directly from the SU~L.I and combines the tunnel with M open-air plaza, including landscaping and a fountain.

A bundled tube frame is the ~ r ima rv lnrcral svstem for the 71-storv 296-111 1972-ftl- 1211 186.OUU.m' I? mtliton 11') .iilisd 63nk lorie;. The shape is forme> by luo'quanr;- circlcs placcd ~nus)mmctricall! bout thc m~ddlc tuhulir line. Tiis colun~n sp~cing5 brc

1.57 m ( l j it) \kith the usuil tres-l)pe construction. Thc systcm ilso uses irvo v~micll trusses in the core, which are connccied to the exterior tube by outrigger and belt wsses. Sienificant imorovemenl in tubular behavior is obtained bccause o r the oarticioation of - the INSSeS. This sysrcm, thcrcrorc, embodies elements from the framed tube, bundlcd tube, and truss rystcme with bcit and ouvigger trusses. The truss system provides another transverse frame linkage in the curvilinear part to improw its shear lngchnrnctciisticn.

The structurai system for the Allied Bank Plaza towcr was sclcctcd after study of both steel and composite systems. Tite system permitted a substontially reduced con- swct ion time. The tower's form and slcndcrness arc a radical departure from past rcc- tnngularbuildings of this height. yet the inherent rigidity or the bundled tube system dc- veiooed for the tower limited stccl w c i ~ h t to 128 ke/m2 126.2 nsn.

cant reductions in design wind pressure belorr' that experienced by square or rectangular rorms. The tower is founded on a 2.9-m 19-ft 6-in.)-thick mat roundation aooroxi- malely 20 m (65 ft) below grade, which pc;mits utilization of four lowcr lcdels for necessary retail, mechanical, and parking lunctions.


4 ~ 5 HYBRID SYSTEMS

Tall buildings hdve been lraditionllly designed lo n l o k use of 3 rlnglc type uf Inlcr~l In3d resisting system-inttially s~mplc moment resisting frames 2nd then shcar wall s\,rtcms and frimed rubes. Until ~h r . advent of economical, c3sy-lo-use. high-capacit) cbmouter hardware and software. structural svstems had to be amenable to hand calcu- I;ttioc or cumpuler an ;~ lys~s usit~g limitcd-c:tpacity nlach~nts. Notvnda).~ computcr ca- pacil) l s nu1 ;an issue, and decisions on slructural syilcms art made on 1h~'basis of1h:ir r.ficcts on the xppcdrance and funclioning of the building and on its cnnaln~ctahil~ty. This is not to sieeest that on,*l/~i,in~ is nc&otable-lhe e&ineer musl still be aware of

& & . " - 111,: pi1p~II5 ofcrc3ting ;~brupt discnntimriticr in building sliffncrs. the Ions-tcrm cffecls nf dilf:rcntial ixi31 siloncninp. and other side effccl, of using mired systems and multiple materials.

An excellent examnle of a hvbrid svslcm is the O~~e r sea s Union Bank Center in Sin- gdporc. Here :. b r x t d stcvl fr:,n:c rvas used b:causc ofi ls lightnos. lnng sp:inniog ihd. )I!, small metnbcr aizss, absence of crccp shancning. and. combined with ioncrcle a h e ~ r tralla. for iL\ rc r \ cost.r.fficicnt contribution to l>ltral s t iffn~ss.

Another tvoe of hibrid svslem eaininr! oooulsritv is the concrete-filled steel lube , . " - . . column, u.berc lhe r.rcct3bility of n str.ci framr: is 111iinlaincd. but the cos l .~ f f cc l i~~c 3 , -

i;! In-d uapacily ufhiglt-rlrcnpth concrete is u ~ e d The stecl tube pruvidcs cunfincmcnt lo the concrelc much more eificiently than normal reinforcement does, and it is on the extreme outside. where il is most effective. Of course fire orolcction must bc considered. If the slecl tube is considered ns sacrificinl in a fire, then inlernal reinforcement sufficient for the reduced loading normnlly prescribed for the fire limit state must be provided. If external fire protection is provided, lhcn internal reinforcemcnt may not be needed. If concrete can be oumocd into the column from ihc base of each Dour. then a . . . number ofstorics can be concreted at one time and vibration of the concrele is not necessary. Examples of such a system are Cnsscidcn Place. Melbourne, and Two Union Square. Seattle.

The rrends of modem architecture sometimes force the structural engineer away from convention in a search for a struclure that will nccommodale ocsthctic and functional demands while meeting struclurnl requiremen*. The result may be a structure which on one face of the building is of a different type than the other faces, as in Geor- eia Pacific. Atlanta. or a S I N C ~ U ~ ; with a number of quite different clemenls formine i s Lateral load resisling frame, an exccllenl example being First Bank Place. ~ i n n e a ~ o l i s . Here the engineer has provided a braced steci core connected via outilggcr beams to large high-strength concrete perimeter columns, incorporating cast-in fieelwork lo aid erection and connection. Although this systcm provides in-plane stiffness. its lack of torsional stiffness required that additional measures be lakcn. which rcsultcd in one buv oi tr.ruu.ll cxterior hr:lcinp 2nd ;i iturnher ui l:vcl. of pcriln~.lr.r \'lerc,dr.cl 'b..o- J.iges."-pr.rl~aps unc of lhr h~.rt caamplcs of the an uf$~ructural cngin~'rring.

Wilh t l r adtctll of high-r~renglh cottcrcle [uuncrclc ;1buv~'50 >!PA or (70UU psi,] 113,

come ihe era of the "sipcrcolumn." where the stiflncss and damping cnpabjlities of larre concrete elements are combined with the liehiness and conslructabilitv of stecl li:unus. I-l~gI~-r~rungtlt uortcmte. \$hen 11 irlclrrdu, silicz fumc ;mi 3 high-rarrge ivu:<r r d -

du:x ~sopr.rpl;~*lic~rer). exhihits signifir;tntlg lnsrer c r q and shrinh~ge ;!nd l a ihcr~.- iurc ~nurs readily accu,nntndnl~.d in 3 1h)bri~l frsme. 'Thc rel:itivc clic:!pncss of hi$- strength concrete together with the facl that large members do not require large cranes (or any cranngc at all ifpumped) mcans that thc columns can be economically designed lor stifiness rather than for strength.

Sect. 4.51 Hybrid Systems 301

The Intcrtirst Plaza in Dallas (not described in this Monograph) uses supercoiumns in conjuncrion with an almost conventionai steel frame, and the Columbia Seafirsl Ccn- ler in Scatllc incorporates very large supercolumns connected by slecl diagonal members.~? a braced steel core. Another example, although never built, is the Bank oTt11c Sou*\t.est tower in Houston. Hcrc eight giant concrete columns form the chords of four vcrtiFi\ steel megawsses.

The orcvious cxamnles sueaest that hvbrid slructures are likelv to bc the rule rather . . I I I ; ~ the exccplion for'luture r e g 1x11 buildings, a hsther lo crest; scccplahle dynaloic ~ l ~ i ~ r ~ c I ~ ~ r i s t i c s or 10 ilccun~~nodatc thc cu,npie\ .Il:tp~.s dtm3ndvd by modern ;!rchilcc- ture. Hybrid structures are not somcthlng be tackled by the novice cnginccr armed with a oarveriul microcornouter and a structural nnalvsis software oackaee. as a sound ' u

knowicdgc and undcrstanding of material behavior (such as ductility, damping, creep. and shrinkage), which is not included in analysis and design packages and mostly no1 codified. is essential and construclabilitv must bc a oarallel consideradon. However. \vithour hybrid structural systems many of our modern tall buildings may new1 have heen bull1 in their presenl form.



Overseas Union Bank Center Singapore


Year of completion Height from street to roof

Number of stories Number of levels below ground Building usc

Frame material Typical floor live load Basic \\find velocity


Design fundamentnl period

Design damping Earthquakc loading

Type ofstructure


Typical floor

Story height

Beam span

Benm depth

Beam spacing

h'lalerial Slnh

Columns Sire at ground floor

Spacing

htoterinl Core

Thickness at ground floot

htalerinl

Kenzo Tange and Unec/SAA Poflncrship

Meinhardt Asia Pty. Ltd. 1986

280 m (919 it) 63 4

Commercial. rctuil, office Stccl with concrae walls to sL-~irs and core

2.5 kPa (50 pso

37.7 mlsec (84 mph). 1000-yr return

448 mm (17.5 in.) 7.3 scc

1% ser\'iceability; 3% ultimate Not applicable

Hybrid system of steel frames rvith concrctc ~ i ~ s l l ~ to incrcasc rigidity

Silty sand. sandstone. siltstone, claystonc

7 caissons 5 lo 6 m (17 to 20 it) in disme- ler. 100 m (328 i t ) deep. belled to 9-m (30- f i ) diameter

4 m (13 it 1.5 in.) 20.3 m (66 ft 7 in.)

950 mm (37.5 in.)

4.32 m ( I4 it 2 in.)

Steel, grade 50 and 43

150-mm (6-in.) concrcte on metal deck

800 by 600 mm (31.5 by 31.5 in.) Varies

Steel, gndc 55 and 50 Hybrid stecl frame with concretc wall zoncs

600 mm (24 in.)

Slccl. gnde 55 and 50; concrete. 45 MPa (6400 p i )

The Oversear Union Bank Ccnler (Fig. 4.154) is a prestige state-of-the-art dei,elopmcnt designed to house the bonk's lleed oflicc and provide renval office, commciciul, and


parking space in Raffles Plnce. Singapore. The high-rise section is conceived as two vi- sually scumate triangle towers (although structumlly integral) facinp. each other on the ~. hvooienure. A service core and a wiani~e column in one comer oroAde suooort for the , . - . . higher tuwcr. The loner tower is supponcd on n smaller triangular colutnn and no L- shaped column. The slructurc has hei~ht-to.width ratios of 10:l on the south cluvxion and 8:l on the north elevntion. he hirh-rise structure ~rovides column-free soace throuehout its full heieht above nround 6 i r . 4.155). . -

The high-nsr slruclurc is framed using high-jicld structural steel. The princip,l rolumnr we fabricated box columns framing the cieratur ,hafts and flanged T si12pea IU

conform to the wall lines and minimize encroachment into the elevator shaft arca: Simply supponed stt.el w s r r s 950 mm (37.5 in.) dccp spaced at4.32-01 (14-it) ceo-

ters in an cast-west direc1i.w support the large column-free areas. These trusser xrc dcsigned to act compositely with the concrete floor system.

The floor system consists of areinforced concrete slab composite with a 63-mm (2.5- in.)-deep ribbed steel deck. The concrete slab is a total of 150 mm (6 in.) thick in order to maintain a sufficient concrete thickness, after reticulation of services. for the rcquircd fire separation between levcls. Fire protection of the s s e l frame is provided by lipht- weirht mineral fiber (Firs. 4.156 and 4.157).

The high-rise structu& is supported on h total of seven caissons ranging in depth from 96 to I10 m (315 to 360 ft) and in diameter from 5 to 6 m (16.4 to 19.7 ft). Thc caissons are belled at their bxse and carny Lheir load in end bearine on solid rack

Development of the most efficient siucmrai system is the essintial prerequisite to optimization of the design. The choice of ryslcm drsmatically affects the quality of the material required in the design.

The family ofstructural systems based on the tubular concept has provided the types most widely used to date for high-rise and ultra-high-rise structures. However, it has become necessary to seek new structural systems lo respond to changes which have taken place over the last decade, including the very strong influence on high-rise buildings of evolving architectural forms with many large open arens which extend through m;ltiple floor heiehts.

'The d'ecision to use structural strcl in lieu oiru~niorccd cuncrelc for thc?SO-m (91% (1)-hlph OUB tou'cr e a s dicta1c.d by ruuctural consideralions rxhcr t h ~ n ecnnunlics (Fig. 4.158). The following are the principal f3ctors that dcturmincd the ndoptiun o i structural steel in lieu of concrete.

I. T h e asymmetrical geometry of the.structure resulted in higher stresses in the columns supporting the higher triangle thnn in those supporting the lowcr trion- gle. This caused unequal column shortening from creep and a consequent lateral movcmem of the slruclure.

2. Differential movement (creep) occurred between the reinforced concrete supcr- columns in the primary megasystem and the swctural steel secondary system within the portal frames of the megastrcturc.

3. The dimensions of the vertical structur~al members had become gross. resulting in loss of floor space and presenting substanrial planning difficulties, both archircc- turally and in the distribution of building services.

4 . Tile sujl conditions were poor. jnd :! sp:cihl and cos~l'y fnusdatinn wr.3~ nccus5:lry. Structural hIcrl kccpr \he weight down cu~npsrcd lu v cuncrct: stmcturc, rsdu:. Ink buth the difficulty and the cost of footingr.

5. 'The use uf high-yield steel restllted in light:r, snlaller, and leas cnstly structural nlembcri nhich svuuld sa~isf> the system stiifncas crilsria.

Sect 4.51 Hybrid Systems

LEVEL FLOOR

R I S E

L O W R l S E FLOO"

E L E V A T I O N

~ 1 6 . 4.155 ~ ~ ~ r n i n g p l ~ n r nod elcmlion; Ovcrscns Union Bunk Ccnlcr. I


SERVICES ACCESS 1

/ LIGHTWEIGHT FIREPROOFING

Fig. J.156 Flctor plan: Olcrrcns Union Dunk Ccnlcr.


The composition of the structure is one where lhe stcel frame provides the skelcton ofthe structural system, with the bracing and reinforced concrete walled zones acting to increase the rigidity of the building (Fig. 4.159).

The individual elemena (steel frnme and concrele walls) nre both capnblc of func- tioning independently in the trnnsfer of vertical loads from the top lo the foundations. However, as elements used in conjunction. h e concrete provides restrain1 to the slecl. allowing the steel frame to be fully stressed as an isolaed component.

Control of dilferential creep between concrete and smctural steel was investigated extensively, taking into considcrntion axial shonening of the 5 t ~ ~ l u r a l slcel columns. the construction program, and the bracing of the steel smcrure during erection. The likely stresses in the concrete elements and thc steelwork were considered in both the short term and the long term. The analysis indicated that the oplimum was for the concrete clemcnls lo follow behind the steelwork by approximately four lo five lcvels. The maximum allowable differential was the concrctc elemcnls lagging 24 levels behind the steelwork. The final optimized solution for the OUB structure is a mixed-frame hybrid structure, providing an effective SlNClUrc utilizing the hest properties of slccl and concrete to achieve the minimum cost.

Fig. 4.157 Piun of reinrorccd concrcle wollr: Orerreus Union Bunk Centur.


Hhbrid .,truclurs i n nunhg n f cottaidsra~iun as 3 cnttsciot>r design ilppr03cl1. 7.111: US?

01 reittfurccd coucrstc ulsmcne lo contrul thc dcflcclion and dynamics o f lo l l steel 51mc- turcs provides an effeclive altcrnadvc smclural svstcrn that bill ailow the dcsiener to " -

malrerull use o f the higher allowable stresses o f 'high-yield steels when other bracing systems are inefficient or unacceptable architecturally.

TYPICAL FRAME

PLANT F TRUSS

BRACED

:LOOR

fig. 4.158 Slrutturirl r l c c l ryslunl; O ~ u r l r i ~ r Usian Bunk Ccster.

Sect 4.51 Hybrid Systems

TYPICAL -R.C. SHEAR WALL

Fig. 4.l5Y I'rinlurysl,cur $~u l l syslcrn; 01.errcus Uniun nonh Cunlrr.

Citicorp Center New York, N.Y., USA

Architect

Slructuml engineer

Lateral Load Resisting Systems [Chap. 4 I Sect. 4.51 Hybrid Systems

daring appearance, with all four of its corners jutling 0 ~ 1 2 3 m (76 it) unsupportc~ Crom only four exterior columns, one centered on each side, which free-stand for a he~ght of 34.7 m (1 14 it) at the base (Fig. 4.160). The central core also suppons the tower. This

Hugh Stubbins and Associates with unique structure was not designed this way arbitrarily just lo achieve a dramatic effect.

Emery Roth nnd Sons Thc site. a city block in Manhattan, was purchased fully except for St. Peter's Lutheran

LeMessurier Consultants with office of Church on one comer of the block. The church agreed to sell its air rights, but would

James Rudeman Year of completion 1978 Height from street to roof 279 m (915 ft) Number of stories 60 Number of levels below ground 3 Building use Office, retail Fmmc material Steel Typical floor live load 2.5 kPa (50 psf~ Basic wind velocity 41 d s e c (92 mph). 100-yr return Maximum lateral deflection HI600 at I-Wo ( 2 0 . ~ ~ 0 seniceability load Design fundamental period 6.9. 7.2 scc Design acceleration Less than 20 mg peak. 10-yr return Design damping Measured 1.1 and 0.9% serviceability in-

creased by TMD to 4% each direction Earthquake loading Not applicable Type of structure Braced perimeter tube with braced core

below 9th floor; TMD at top Foundation conditions Manhnnnn schist Footing type Steel bore plates on grout on rock Typical floor

Story height 3.89 m (12 ft 9 in.) Beam span 10.3, 12.8 m (33.9.42.1 ft) Beam depth 530 mm (21 in.) Beam spacing 3.81 lo 3.91 m (12.5 to 12.84 ft) Material Steel, grade 350 MPa (50 ksi) Slabs 63-mm (2.5-in.) lightweight concrete on

76-mm (3411.) steel deck Columns Pairs of 965 by 762 mm (38 by 30 in.) max

by 3421 kg/m (2294 Iblft) at 5.74-111 (18.83-ft) centers at center of each side of building

Material Steel, grade 350 MPn (50 ksi) Core Moment frame above 10th floor, braced

frame below Materiol Steel, grade 350 MPa (50 ksi)

This 60-story tower contains an area of 102,200 m' (1.1 million it') of the project total of 167.200 m' (1.8 million ft'). The 47.8-m (157-ft) square lower has a dramatic and


allow no columns of the office tower to pass through its facilities, and it required that a new church building be designed and constructed in that comer with its own distinct identity. This last requirement led the architect to place the first office floor more than 46 m (150 fl) above the streeL

The most direct and economical way lo achieve the 23-m (76-it) comer cantilevers on each face of the typical tower floor was to provide a steel-hmed braced tube with a system of columns and dingonnls in compression, channeling the building's gravity loads into a 1.5-m (5-ft)-wide "mast" column in the center of each tower face [Fie. . u 4.161). The main dingonnls repeal in eight-story modules. The compression diagonals are restrained by horizontal tcnsion ties at four-story intervals. This system brings one-

~ ~ ~ ~ ; ,

, , . Fig. 4.161 Eic~.utiun; Cilicorp Ccntcr.

Sec t 4.51 Hybrid Systems 313

half of the tower gravity load down to the four base "legs," one centered on eoch side. The svslem. because it rcoeals an each face of thc tower. is also very cflicienl in resist-

~ ..- - ,~ . iug wind lorcus, hoth shcar and ovcrlurning, slnce il forms a cumpieke brncsd lubc. A ncal rtructural touch rvar the omission of the corncr columns at Ihc floor just bduw lllc main a i a~ona l inlcrsection uith thr corner cvrry cichl storics. This was to avoid accu- . - mulating gravity load in the corncr columns and gives unobstructed corncr views as a bonus.

An 8.8-m (29-it)-deep perimeter truss on top of each of the legs carries the gravity lnadr ofthe lowest seven floors to the center lees. The wind shear is transferred through -

the tenth-floor diaphragm at the top chord level of this truss over lo the diagonally bnced elevator core, which carries it down to the foundation. Wind overturning forces continue from the superstructure mast columns through the legs to the foundation.

The tvoical office floors arc framed with convendonal steel beams, with a light- .. - , , weight concrete slab on clcctrificd undcrfloor slcei deck (Fig. 4 162). Thc core has mo- rns~~~-cunncctcd lr3mus in nrdcr lo provide a syrtsm to delivcr floor-by-noor wind lorccs lo the h r~ccd tube pancl poine occurrin~ cvcry lounh story. and lo allow $honer . . - . unbraced lengths ofthc main compression members.


The wind tunnel study for the tower, conducted by the University of Western On- tario. Canada, indicated rhat persons on upper floors ofthe tower t~~ould experience un- comfortably high lateral sway accelcrations in wind storms. In order to reduce nccclcrations to acceptable levels there were only t\vo possible approaches: add a great den1 of mass and latcral stiffness withour increasing the natural vibralion period, or add to thc building's natural damping. The first approoch would lrave cost about 55 million. whcrsas the second approach \vould lhavc required increasing the building's damping from about 1 to 4% and designing and constructing the \r,orld's firs! tuned mass da~npcr (TbID) of anywhere near lhis size. Tllc second approach was adopled at a final cost of less than one-third of the first approach. The inilial step was to convince thc arcl~itect and owner; then the slruc1ur;ll cngincer hod to find a \\,a). to actually do it. Fortunately. LeMcssurier Associalcs u r r c able lo cnlisl the technical assislance of Prof. Alan Dav- enport of the University of Westcrn Ontario. Prof. David \Vnrnmley of M.I.T., and tllc firm of MTS Systems Corporation of Minncilpnlis. The lauer firm provided the detnilcd mechnnicsl. clectricnl. and cuntrol system design and also constructed the TMD systcm. with the assistance of HRH Conslruclion or New York. the general contractor. The TblD is located an a dcdicalcd floor at 242 m (793 it) above grade, near the top of the towcr. for maximum cff~crivcncss. The Citicarp tower was dcsigned from the beginning to have the ThlD system. The system used includes a moving 373-tonne (4 In-ion) concrete-mass block tl~at slider binxially in the norlh-south and cast-wcst directions nn pressurized oil hearings on polished stecl plates. Tlic m a r is conneclcd to the building structure ria long t c c l boom struts, prcssurircd oitmgcn springs, and hydraulic scrvrl aclualors. The lateral atiffncss of the spring elements makes thc systcln inlo 21 clasrical passive spring-mass rystcsi. \\'hich basically is tuned to the same frcqucncy as thc tower and acts as a vibration absorbcr lo effectively incre:~sc the building's energy absorption. or damping. The TAlD reduced accelcrations lrom wind-induced motion by 40 to 505b. 11 is designed solely to increase occupant comfort. The building is dcsigncd for and strength as if the ThlD were not there. The TMD syslcm has pcrformcd very well since its installation and has weathered many wind storms and cvcn a hurricane.


CenTrust Tower Miami, Florida, USA


Year of completion Heighr from rtreel to roo1


Building use Frame material Typical floor live load Basic wind velocity Maximum lateral deflection


Design acccleralion

Design damping Earthquakc loading

Type of stmclurc

Footing type

Typical floor

Story height

Beam span

Beam depth

Slab

Columns Size at ground floot

Material

Core Material

I. M. Pci and Partners CBM Engineers. Inc.

1985 178 m (585 it)

48

None Office Concrete

2.5 kPa (50 psf) 54 mlsec (120 mph) 508 mm (20 in.)

3.50,4.50 rec

Not calculated 2% serviceability: 5% ultimatc

Not applicable perimercr partial tube with interior shear walls 2.1- to 2.4-m (7- to 8-ft)-thick mat on precast piles

3.81 m (12.5 ft) 14.6 m (48 ft) max 508 mm (20 in.) with 813-mm (32-in.) haunching

Concrete joists at 1.8-m (6-ft) centers and 114-mm (4.5-in.) slab

1600- to 1220-mm (63- to 48-in.) diameter at 3.57-m (15-ft) centers 48-MPa (7000-psi) concrete

Shear wall, 610 mm (24 in.) thick maa 48-MPa (7000-psi) concrete

Ovedooking Biscayne Bay. the 48-story CenTmsl Tower adds a unique shape to the skyline of downtown Miami (Fig. 4.163). Thc building consists of a 37-story-tall office tower set on lop of a block square 11-story ~ar l t ing garoge. A quarter-circle in plan, the office tower's arc steps back three times as it rises up.The 90° comer of the quarter-circle is chamfered to create an additional 25.9-111 (85-it)-wide face of the building. The garage also serves Miami's convention center and has a people mover station on its fourth floor. On top of the garage, the building carries a large landscaped area, including a refleclion pool


The building is conslructcd in reinforced concrete. Floor framing consists of 520- mm (20.5-in.)-deep pan j0iSls. spanning up lo 10.7 m (35 11) and supporied on 11.6-m (48-it)-long haunchcd girders. Ocplh ofthc haunched girdcrs varies from 520 mm (20.5 in.) in the middle to 813 mm (32 in.] at tllc ends.

Thc three 4.6-m (15-11) Slcp backs at the circular face of the building are locolcd at floors 20.31. and 46, as shown in Fig. 4.161. Con\,entional girders are used to transfer the columns at floor46, but at floors 20 and 31 an unusual one-floor-dccp brackcl is employed to transfer each column. A normal marc of transfer girders would have rcsulled


in a loss of lease space at both of thcse floors. The location of transfer columns and brackets at the twentieth floor is indicaled in Fig. 4.165, and a typical one-stded brackel from the perimeter column is shown in Fig. 4.166.The gravity column loads at the twentieth floor range between 13.300 and 17.800 irN (1550 and 2000 tons).

UidSr column load the bracket requires lateral bracing, which is provided in the form of wall sltear panels between floors 19 and 20. Where a wall shear panel aligns with the bracket, compression and tension chord forccs are directly anchored in tllese wall pnn- els. Such tension chords at floors 19 and 30 are prestressed with an effective force of

Tower axis is 45 degrees o f f garage axis. Because the columns of the curved wall describe an arc in the garage, their spacing is wider than those on the straight walls to accommodate the parking bays.

Fig. 4.164 Pcrin!clcr column 1n)uuL; CcnTrurt Tsacr.

318 Lateral Load Resisting Systems IChap. 4

11.136 IiN (1250 tons). For the other brackets. these chord forces are transferred to the wall panels via floor plates acting as in-plane diaphragms.

The floor slab over pan joislj is increased from 114-mm (4.5-in.) normal thickness to 190 mm (7.5 in.) at floors 19. 20.30. and 31 to provide required strength and stiffness for the in-plane diaphragm forces.

A partial framed tube at the perimeter of the tower and minimal shear walls in the core are provided for the lateral load resistance, causing least interruption in the flow of traffic in the garage and a minimum loss of parking spaces. Shear walls are transferred

shear panel between liwrs 19-20 and 30-31

Unusual eccentric transfer brackets at the 19th and 30th floors transfer wind and gravity loads directly to the perimeter columns. Plan of 19th floor is shown here; 30th floor is similar.

Fig.4.165 Trunrrcr flour phn; CenTrurl To\rer.

t,

[ Sect. 4.51 Hybrid Systems 319 1.

tu culun~ns 11 the lcnth fluor 01 the fsr;ige lo iacilit3tc tr.lilic flos\,. 'The p~r~i;~l lr:!mud ~ u h c ir c~r r led through thc giir~gc i~nd designcd lo resist the cntire 131~131 loads in th~. carnac ;IS rrcll. The nnrual fran>:d t ~ h c consirts of 1%" ~ I ~ ~ n n ~ I - s B ~ p ~ d r r i t l n~ .~ (~lith b - rnlt~mn.; st 4 6-n~ 115'-ft) centers linked bv frames alone lhe circular arc and the cham- .. ~~~ .~ ~ , - fered face. with the columns spaced at 8.6 m (28 f t 3 in.).

Columns in thc garage are 1067 by 1880 mm (42 by 74 in.) rectangular and 1372 to 1067 mm (54 to 42 in.) in diamctcr round. Columns in the totver vary from 1067-mm (42-in.) diamctcr at lower floors to 761-mm (30-in.) diameter at the top. Spandrel bcams nv. 016 rnm 176 in 1 decn in the tower. but varv in dcoth at the carace floors from 1372 -. , ...... ,-- ...., ---r .~~ ~~~- ~~ , - - mm (54 in.) at the three stmight sides to 813 k m (3- in.) along the circular arc due to headroom requirements. Concrete strength in columns and spandrel bcams rnngcs from 49 lo 28 MPa (7000 lo 4000 p i ) , but is keptat 28 MPa(4000 psi) for the remaining floor framing.

The lower is supponcd on a 2.1- to 2.44-111 (7- to 8-ft)-thick mat foundation bearing on 350-mm (14-in.) squore precast piles. Gangc columns are founded on spread footings.

I Elevation u the floors act as diaphragms restrained between vertical shear elements. -

Ftg.4.166 Column trnnrrcr dclnil; CcnTrurt Toncr


Columbia Seafirst Center Seattle, Washington, USA

Architect

Structural engineer

Year ofcomplction


Number of stories


Building use Framc material


Basic wind velocity



Dcsign acceleration Dcsign damping

Earthquake loading Type of slruclurs

Typical floor

Story height

Slab

Columns

Chester Lindsey and Associates

Skilling \Yard Magnusson Barkshire. Inc.

1985

288 m (947 it) 76

6

Retail, commercial, parking, offices Structursl steel with composite stecl-con- C ~ C I C columns

2.5 kPa (50 psO

34 mlscc (75 mph)

483 rnm (19 in.). 100-yr rclurn

5.3 sec

20 m g peak. 10-yr rcturn

2.510 including dampers lor 10-yr rcturn; 2.0% ignoring dampcrs for 100-yr rcturn

Z = 0.75. C = 0.03, K = 0.80

Braced steel corc incorpornting viscoclas- tic dumners: trianculnr corc is linked bv - diagonal steel members at its corners to 3 lerge steel and high-strength concrete

3.5 m (I l ft 6 in.) 50-mm P i n . ) concrete on 50-mm (2-in.) steel deck

3 major columns. 2.44 by 3.66 m (8 by 12 it) at ground floor

Concrete, 66 MPa (9500 psi) Braced-stcel rigid fmme with arches up to I I stories tall transferring load to composite columns

This innovative skyscraper has just 73.24 kplm' (14.97 psO of structural stccl and three com~osi te columns o l ultra-high-streneth concrete. It uses both materials in their most efficir.nl manner. TILL. btulding is cumplelelg 1r:lm:d i n strurlur~l rlucl. \\'lnd and ~.nrtIl- qllak~. loi!d* arc r~..i(t:d h! it ~ t r t ~ c t u r ~ l ~ I C C I innnlcnt r~.slsting hnc~.d i r ~ m c , a l u c l ~ I., triangular in shape and locatcd in the interior core.

Exterior windows are unobstructed. Compositestructural steel and concrete columns are located at the vcrticcs of the triangular core to carry a large portion of the vertical loads. reduce wind swny, and resist seismic forces. At thc base of the structure, tllcse composite concrete columns are 2.44 by 3.66 m (8 by 12 it) in dimension. The concrete strength is 66 MPa (9500 psi). The sway of the building is limited to Hl600. The floor

sect. 4.51 Hybrid Systems 321

framing for the p l an , arcade, and parking levels is a 114-mm (4.5-in.) concrcle slab o\,er 76-mm (3-in.) metal deck. Abot,e the plaza letel, the floor framing is 50-mm (2- in.) concrete slab over 50-~nrn (?-in.) dcck. All stecl floor bcnms arccomposite with the concrete slabs.

Th'e'skyscraper conlains 135,415 m2 (1,457.561 ft2) of office space and six below- p d e levels of parking for 536 cars with an area of 29,670 m' (319.368 fs). Public

~ i g . 4.167 Columbtn scufirrt Ccnler. seutfl~, ~ a ~ l ~ i ~ ~ t o n . (Courier). olSkilliag. IVord Afosnurron Bnrlrbire. Incl


arcas consist of a lobby levcl containing an area of 1825 m' (19,641 it2); four shopping levels with a total area of 13.948 m' (150.135 ft'). featuring retail and c o i - mercial space; n multilevel shopping arcade which is open 24 hours a day; a multilevel landscaped plaza surrounding the entire office tower; as well as an underground pedes. trian tunnel connecting the building to another office building across the street.

Columbia Center's excavation was the deepest ever undcrtakcn in Seattle. It reached 37 m (121 ft) below Fifth Avenue and 21 m (70 ft) below Fourth Avenue. Complicating the task was the requirement to protect an existing five-story office building at the Fourth and Columbia comer of the building. The shoring wall was constructed by drilling 12-11? (4-it) holcs at 4 m (13 ft) on ccnter to at leas14.3 m 114 ft) hplnw the hn?- ,~ .., -- --.- tom ofthe excavation. These holes were fillcd with lean concrete and n pair of 350-mm (14-in.) wide-flange steel soldier pilcs. Tiebacks wcrc placed in the normal manner between the pair of vertical soldier piles. 150- and 200-mm (6- and 8-in.1 wood lanvinn was used lo support the earth bcrween the pair of soldiers piles spaced 4 h (13 it) a p a n The building structure design underwent thc scrutiny ofextcnsivc testing inn wind tunnel at lhc University of Wcstern Ontario, Canada, for both static and aeroclostic loading. The acroelastic tests mcasured the twist, sway, base shear, and acceleration of the building. They showed that thc building performed very well in the wind. but revealed that the accelerndon of thc building in a major windstorm might bc felt by a portion of the occupants. Viscoelvstic dampers to absorb wind energy were added to thc moment resisting braced frame to eliminate this possibility of uncomfortable acccleration.

:. :I

! Sect 4.51 Hybrid Systems 323 ,

First Bank Place Minneapolis. Minnesota, USA

$ Architect

: Smctunl engineer : Year of completion i Height from street to roof

,: Number of stories

,' Number of levels below ground

: Building use

: F m e material Typical floor live load Basic wind velocity


Design fundamental period Design acccleration

Design damping Ennhqualie loading

Type of structure



Story height

Benm span Beam depth

Beam spacing

Slab

Columns

Material

Core

Pei Cobb Freed and Partners. lnc. CBM Engineers. Inc.

1992

236.5 m (776 ft) 56

3

Office Steel with concrete supercolumns 2.5 W a (50 psQ

36 d s e c (80 mph) 533 mm (21 in.) 6.48, 5.26 sec

24 mg peak. 10-yr return 1.25% serviceability; 1.5% ultimate

Not applicable

Spine structure, supercolumns, and braced frames with Vierendeel "bandages"

Rock, 7.5- to 10-MPa (75- to 100-lon/ft2) capacity Unreinforccd rock footings

3.96 m (13 fl) 10.97 to 18.28 m (36 to 60 ft)

406 to 838 mm (16 to 33 in.)

3.05 m ( I0 ft)

133-mm (5.25-in.) lightweight concrete on 50-mm (2-in.) metnl deck

2160 mm (84 in.) square at 23.24-m (76- R) centers Concrete. 68 MPa (10,000 psi)

Braced spine. A572 steel [350 MPa (50 ksi)]; column size 1067 by 914 mm (42 by 36 in.) to 914 by 610 mm (36 by 24 in.)

A 236-m (776-it)-tall 56-story chiseled rosrcr i, the t;illcst of il~rci. distinct-looking hul intcgral buildings which form First Bonk P1:lcc (Fig. J I 6 8 ) . The laver is crowned w t h a 13.7-1" (45-ft)-lti~h ctrculnr grid of stscl uhich c~nti luwra 6 m (?U fl) out rrom a \.<I- tical plane nnd cokcals coolkg towers and antennas. At the second floor (the Min- neapolis shyway level) the tower connects to buildings on adjacent blocks via two bridges. One of Ulese bridges is a classic tied arch, which is braced from buckling by an inverted pony wss . Adjacent and connected to the tower is the 68-m (224-it)-tall 14- story atrium building so called because of the six-story 27-m (89-8)-diameter atrium at

Fig. 1.168 Firrl Bunk I'luee. >linnropuiin, hlinnanln.

Z!? i.

$7 a::, ... i . ' sect. 4.51 !:.

Hybrid Systems

its base. One-fourth of the pcrimetcr of this atrium is a glass wall supported by Vieren- dcel pipe trusses. Some 12 m (40 R ) above the atrium floor is centered an 18.6-m (61-it)- diameter ring beam which supports the columns of the l c n e space Floors above the atrium. Filling up the remainder of the L-shaped site is an 18-story 84-m (776-ft)-la11 "park; building, which overlooks Hennepin County Government Center Park. Under- neith"i~lke perk building, atrium. and tower is a three-level 450-car basement parking garage. The First Bank Place complcx has 130.000 m' (1.4 million f$) of floor space

. (Fig. 1.1691. : Thc backbone ofthc First Bank Place tower is n cruciform-shapcd spine anchored by ? steel and concrete composite supercolumns, which are linked to one another with a vcr- '1 tical shear membrane formed by steel bracing in the core of the building and o!tr!gger

bcams beyond the core moment-connected into the supercolumns. Charactcr~stlc of : spine structures. Ihcse supercolumns extend unintcrmpled the full height of the build- , ing. They vary in cross-sectional area along their length from 7 m' (75 ft') at thc base lo

4.6 m' (50 11') at the top. Torsional s~ability lor the tower is provided at the perimeter ofthe building by a dun1

system 01 unsymmetrical diagonal bracing and Viercndeel bandages. The single dingo- nal pcrimetcr braces extend from the third floor to the forty-fifth floor in six-stoq-high

(c) 27th lo 45th (d) 45th lo 54th 56th

TIC. 4.169 Fluor [,Inn: First 1l;lnli I'lucc.


sections. Spandrel beams moment-connected through these diagonals, along with the supercolumns, restrain the tendency of these unsymmetrical bmcings lo deflect horizontally under gravity loads. The three-story-deep Vierendeel girder bandages, which are provided at floors 1215.24-27. and 4215. restrain the wamine. which would oth- . -. ~ ~ ~

c w k e occur in the open scc;ion composed of the cruciform spine and pcrimcter bmccs. n t u i e bandagss t r ip l~ lbc lower's tori~onal stiffnuss and incrense i b lateral stiffness by 36%. In addition, the bnndaees are used to Vansfer gravity loads to supercolumns and comer columns. thus increasine the efiiciencv of thebuildine's ovemmine resistance. - - -

Other Vicrrndeslr u e lared in llrc building to cllminalc transfer girders and increisc the building's loreral stiffi~ess. A 12-story Vicrendccl spms along 3n crtcnor h c e of lhe building between a supercolumn and n comer column. transferring a column which supports 28 floors of load. Above the fortv-fifth floor of the tower there is a nine-slorv-tall circular Vlurendccl girder which frames inta supcrcolutnns. lhu curved ~ i c r sndcc l noi only incrcxus the 1;ltcral and lorsionitl stiffness uf ihe lap of the building, bul olso ;!I- lotvs l l ~ ~ circular-shaped ponion o r the buildlng to sir alup rlte squsrc s h p c below \ri\b- out extending additional columns down through the leas; space.

The structural system was chosen over a ~ G m e t e r bracid fmme or a moment fmme to achicve a column-free exterior facade f& thc building. The presence of composite concrete columns cnhanced the ovenurning resistance of the building and achieved overall economy for the structure.

A572 grade 50 steel was used for columns and beams that were controllcd bv 5trcngrh crllerii. 2nd A36 3td:I s.;ts used for inlemller, c~lntrnllcd by .Itfincrs uritr.ri:t. Thc sl~pr.rcolumi~s ultl17.r.d 69- and 55.XlPa (IU.UOO- :tnd hO(lU-PSI) iuncrclc 'The rlc:l col~ll ln h3s~. pl%les b u r on the lop of ihe concrctr. hassment girapc columns. !\l!~ch SUP.

port the posttensioned flat-plate garage floors. Special analGis was performed to as=&- lain the effects of restraint on the posttensioned slabs due lo the presence of large concrete columns supporting the lower loads and perimeter basement walls. All building columns sit on individual footings which bear on rock.

Three-story-tall Vierendeel bandages were provided along line CC' and also along E'D' (Fig. 4.170). The strategically placed bandages not only provided essentially column-Free exterior spans along face CC, but also improved the torsional resistance of the building dramatically, with optimum use of the S ~ N C ~ U ~ I I ~ steel. The perimeter circular Vicrcndeel above the forty-fifth floor provided both lateral and torsional resistance to the entire frame.

Tl~u loa.cr b>sclnr.nt floors a r r c Jcs~&ncd as poitisnrioncd cuncrute flst-plate floorr. The pu>ticnsimcd conslnc~iun \gas csrunti31 lu control cracking in nuur sli~bs because of the cold, snowy winters af Minneapolis.

The building was analyzed in a three-dimensional finite-element computcr model lor tlic following loading condirions:

1. Sequenlially applied dead load consistent with the consuuction sequence of ihc building

2. Live load

3. Three-directional (.T, :, and 0) wind loads dynamically determined from wind tunnel study with appropriate combinations

4. Creep and shrinkage of concrete columns

5. Temperature gradients and differential temperature on concrete columns

During the design, the members were checked for 99 load combinations. In Ille ;onrlrllcuon I C ~ L C I I C ? . t h ~ . ~ n t i l ~ ~ ~ i i t e concr?le colu!~ln 1\15 xlLd\v~d 10 (3g 12

lloorr hr.hinJ cr;clr.d rirl:tor~l rlcel ind six flours bshinJ 111~. concrt t~.d sl;!bs no nts13l

I BRACE I

CRUClFORM SPINE

BRACE CIRCULAR VIERENDEEL ABOVE 45TH FLOOR

12 STORIES VIERENDEEL FRAME

(4 (c)

Fis. 4.170 Fir9 Itunk Ptuce. (a) Structural rystcm. ( b l Estcrnul hmcing. (c) \\'firping-rcstrui~~lrle perimutcr bundi~gcr.


deck. Because of h e presence of unsymmelrical exterior bracing, localized bandages, and the free-spanning Vierendeel above noor 45. the SlNclUre was analyzed to cstablish its performance during the erection process. Both lateral and vertical displncements along with strength were checked.

The strategically placed perimeter warping-restraining bandages improved the torsional performance of the structure dramatically. This is evidenced by the comparison of the torsional rotation (Fig. 4.171) and the lateral displacement (Fig. 4.172) of the stracture due to wind in the x direction, with and without the bandages.

The presence of the three-story-deep perimeter bandages created a localized horizontal shift in h e center of rigidity of the lateral resistance of the structure and thereby


produced internory in-plane diaphragm stresscs. The associated floor diaphragms were nnolyzed lor in-plane shear and reinforced accordingly.

building wns dso analyzed for the reduction in column and diaphragm stiffnesses due to cncliing of the concrete and the uncenainty of the effective modulus of elasticity.

6x displacement (inch) wind in X-direclion

Fig. 4,172 Lnternl dtrplncemcnt; Firrl Bunk Plncc.


Two Union Square Seattle, Washington, USA

Architect NBBl Structural engineer Skilling Ward hl;~enusson Barkshire. Inc.

Year o r completion 1990 Height rrom street to roor 220 m (720 11)

Number orslories 5 6 Number of le\,cls bclor\, ground 4

Building use Office. rct;~il Frante malcrial Steel a,itlt uumpositc cu lun~ns

Typical floor livc load 2.5 kPa (50 p s n

Basic wind vclocity 34 mlscc (75 mph)

hlaximum laleral deilcction 312 mrn (12.3 in.). IOU-yr ruturn

Design fundamental pcriod 6 scc

Design ncccleralion ?U lnlg p~ i lk . 10-yr return

Design damping ?.l"rllO-yr return including damping dc- viccs: 2 .0~~1100-yr rcturn ignoring dnrnp- ing dc\iccs

Earthquakc loading Z = 0.75. C = 0.03. K = 0.8

Two Union Square building proridrd the construction industry wilb many new concepts, materials, and techniques (Fig. 4.173). By locoling the c;!rthqu:~ke and wind re- sistinr elements in thc interior core walls. tllc architect lrad Trcedom that cuntributcd lu - its design. Two Union Souarc rcorcscnts n union oT busincss and communitv. I[ corn-

level plaza with large opcn spaces, relail shops, and restaurants. The desirn team was raced with a number o r uniaue challenres bv this comnlca

lic s ~ a c e s ill the base of rhc tower. Particularly challenoinp was tlte constrnint-filled site. which included existinr structures on two sides. an aciiviinterstale rrccwav adiacent. a . . cily ;I,C?I oter I I ~ U b;~se .ind UIIJ~.~ the tusicr. :,nd r c q . ~ i r u n ~ ~ . n ~ r lor 2 conlp.c\ u ~ c r ic- lure !tit11 c ~ c L . ~ . ~<:~tdri! l l . 2nd 13rp~. h~111Jcrs 513ir .tupping thr.3u.h lhc pl:,,:~.

Among thc many technical nccomplisltments that incrcascd pcrTorm:!ncc. shortened construction time. and reduced ~tructural costs from $28 to SIE million arc the most advanced application of a composite system, the lirst to utilize stccl pipes filled with a n,orld-record-brcaking lhigh-slrcngth 131-hlPe (19.000-psi) concrctc, the most efficient ~,iscoelastic dampers-to control building movcmcnt, and unequaled crtcrior column eoecinrs o r u o to I 4 m 146 Trl. niavidine s\\'eenino vic!vs o r the citv and Puret Sound.

and sited in a seismicufi\~ ac t iw area (arismic zone 3), thc d e s i ~ n ~ r o r i d c d nc\v tech-

needed parking Tor downtown shoppers. a respite i n n busy do\\,ntori,n nrca, scenic viem-


points, an extension of an important urban park, and a nciv network of pathways for [he adjoining neighborhoods. I& cxccplional design has won widespread architectural praise and public popularity and received the Grand Award Tor Engineering Exccllcnce from the American Consulting Engineers Council in 1990.

Fig. 4.173 Two Union Squnre. Sculllc, \\'arPingtun. lCor8nr.r~ ofSkillirrg Il'nrd Alo~nirrrrrn ~ ~ r l - ,hire, i,,~.)


First Interstate World Center Los Angeles, California, USA

.. Architect

Structural engineer

Year of complclion Height from street to roof


Building use


Basic wind velocity



Design acceleration

Design damping

Earthquake loading

Type of structure


Story height Beam span Beam depth

Beam spacing Slab

Columns

Spacing

I. M. Pei and Parmcrs

CBM Engineers. Inc. 1990

310.3 m(1018 rt)

75 2

Office

Swclural steel 2.5 LPo (50 p ro

31 mlsec (70 mph)

584 mm (23 in.). 100-yr return

7.46. 6.91 sec 23 rng pcok, IO-yr remrn

1.25% serviceability; 1.5% ultimatc

C = 0.03. K = 0.8

Perimeter ductile tube with chevron braced core Shale

Spread footings

4.04 m 03 it 3 in.) 16.76 m (55 it)

610 mm (24 in.) 4 m ( 1 3 it)

133- or 159-mm (5.25- or 6.25-in.) lightweight concrete on metal deck 1067- by 610-mm (42- by Win.) WF section. g a d c 350 MPa (50 h i ) 6.1 lo 7.6 m (20 to 25 ft)

Bnced steel; column size at ground floor 1230 mm (48 in.) square. 6308 kglm (4230 Iblft)

Called a signature building for the city of Lor Angeles, the granite clad, 75-story building with its scrrotcdfacadc(Fig.4.174)riscs 310.3 m(1018 it) above street level. It contains about 130.000 m') (1.4 million 11') of office space. At present. it is thc tallest building in seismic zone 4 or its equivalent in the \vorld.

The base of the rower is embellished by Spanish steps \rpith water runnels, fountains and landscaped areas. These steps arc seismically isolated from the tower structure and bridge ihe elevational difference of approximately I5 m (50 fi) in the surrounding nrea along the north to south axis ofthe taa,cr.


The structural system lor the toueer is an a11 steel dual system comprising an intcrac- five braced core and a perimeter ductile moment frame. Thc braced core. ancllorcd at its corners by stccl box columns, is 23.5 m (73.8 11) square. Tllc box colurnns weighing U

m : ~ r i m > ~ m nf 6308 kalm (-1320 lblftl at !he base carry a maximum design gravity laed a f 6- :.:- , 100,QQP.kN ( I 1.000ionsl. TWO-st& chevron bracis free span each of four sides of the

corc.ln'order to achieve an efficient lateral load resisting structural ireme. flours frcc ~ n : m un to 16.76 m (55 it) . looding the interior corc and the perimeter framc columns.

. . . ~ ~ ~ . . resisting fremc.

The slructure is dcsigncd to remain csscntially elastic lor an snticipnled masimsm crcdiblc cunhquakc of magnitude 8.3 on thc Richter scalc at the nearby Sari Andrcas

CORE BRhCI:IG ISOMETRIC


f a ~ l t .?.p;!rt from ;inal!.ling the struct.lre for a con!'?ntion31 5 pur;unt d~ tnpcd r e h ~ n n > e spcctnml fur the n~sxinttlrn crcdihlc earthquake, 111s f~~ l l ow ing spscial analysis otld dr.. sign features usere introduced.

1. Since two-story chevron bracing was used for the lirst time in the seismic region, redundancy i n the gravity structural load path was examined for an accidenrsl buckling of n diaeonal. .

?. The atructtlral rncmbtrh, buth hr.s!nr and columrl~. nurc ttc>t only designed for the grnund ,110ticu1 i!lun: t h ~ . ttgn ortltugunal principal 3,es u f t l v strucutrs, but ;~ l ru ncre chccked lur the dtrcctinnal m:trima due to umnidiruution31 s~ . i sm~c motion

3. Time history analysis was conducted primarily to detcmine maximum interslory drift and the absolute maxima for the horizontal acceleration at floors. The maximum intcrstory drift was used in the design of the curtain wall, whereas the acceleration data wns used for the dcsign of floor-mounted equipment such as clc- vator machincs and \\,aler Lanks. Timc history anal\ssis wns nlso conducted for vsruc31 3ccc I~ . r~ t i ~n . B?sidcs cr~.:lting o\~.r~urrlin"UII?ct~~ :!I 111s t ~ i l n ~ r ~ . ~ fl,,,,~.. an :~ntplifiuatinn o l ~ ~ . r t ~ u l l nccclcr:,tiur~ uuuld lund tu ;L plunying hi lure in t h ~ . tr;lnsfer gird^.^;. ThC 2llalylib $135 ~<5ellli31 IU pcccl~dc \uch 3 i l i l .~,~. mode.

4. I n order to establish a load deflection curve and global ductility limit.., a mono- tonically increasing symmctric nonlinear lateral load analysis !\,as conducted.

5. 1 hc critcriun fur !61ttd t~tutiun s.25 set :!I :trunnd 2 3 r i i ~ fur pc:~k lhori,.0nt:11 :I;;cI. eralloo during 3 otlce in IU )cdrs N ind aturm. Tnc I:~tcr:ll n~o.lc< 01 s thr:ltiun u ere ~ d j ~ a t c d in a ~ i ? , not unly to :tcltie\r. tI1c c~ccup.~lt uomlr,rt :I[ tllc t ~ l n ,lc;unlud noor for the 10 year wind storm. but which r\;ould not incrcasc thc'latcrai rcsponse lo seismic motion.

Sixtccn critical ioints in the braced frame were mcchanicallv stre.; rclie\,cd hv itl;inn ttw ~ - - .~ . . -

Lcun~rd T110,npsun ! ihratiag method o f rtrsrs cclief. Spe:iiil nclding L~ICI t~.stirlg cudurs, ncrc ust;lbl~jhr.d for ;tll sruldcd connsctionr.

The structure is ioullded on shale rock u,itlt :ln ;1llnn3blu load btxrisg rapJclt! o l 7?0 ~ P J (7 5 tonslft?). Thc corr. u l the structure i s sopported on a 3.1 m (1 1 5 i t ) th,ck COIIUIL.IL. mat. and i! p~.riiiIcter rung fuoling is used fur th~. ~ U C ~ I I U rr311te.

i ! Sect. 4.51 Hybrid Systems 335 i

Hongkong Bank Headquarters Hong Kong

Architect Foster Associates

Structural engineer Ove Amp and Panners

Year o f completion 1985

Height from street to roof I 80 m (590 ft)

Number o f stories 45

Number o f levels below ground 4

Building use Office, banking

Frame material Svuclural steel frame; composite stcel and concrete floors

Typical floor l ive load 5 kPa (104 psfJ with some local increases

Basic wind velocity 64 mlsec (144 mph). 50-yr return. 3-scc gust

Design fundamental period 4.4 sec

Design acceleration 20 mg peak. IO-yr return period (typhoon cucnO

Design damping I % serviceability

Earthquakc loading Not applicable

Typc of structure Steel mast joined by suspension trusses acting in p o n d frame action

Foundation conditions Loose fill over marine deposits and dccomposed granite bedrock: granite bedrock up to 40 m (131 ft) below ground

Footing type Machine- and hand-dug caissons to rock

Typical floor

Story height 3.9 m (12.8 ft)


Beam depth 900.406 m m (35.5. 16 in.) steel

Slab 100-mm (4 in.) reinforced concrete

Columns

Size at ground floor 1.2-m (4-ft)-diameter in groups o f four

Spacing 8 groups i n total on grid of 38.4 by 16.2 m (126 by 53 A)

Material Steel, grade 50

Core None

The 20-m (65-ft)-deep basement o f the Hongkong Bank (Fig. 4.175) was constructed using a perimeter diaphragm wall and top-down construction techniques. The superstructure is constructed using structural steel and composite steel floors. Stability is provided by masts, linked at five levels by trusses, the complete system acting as a fi\'e- level unbraced sway frame. Each mast comprises four tubular steel columns linked by horizontnl bos-section beams to create a Vierendeel system (Figs. 4.176 and 4.177).

Lateral Load Resisting Sysferns [Chap. 4 Sect. 4.51 Hybrid Systems

180m

T w o nory deep

Vierendeel mast suspension

Hangers -dl!#EHla 1

BANK 3

Fig.4.176 Sccli<ln tllrougln building; Hungliung D18nli ilcixdguurtcrr

338 Lateral Load Resisting Sys tems [Chap. 4

16.8m .4.6mL 10.8m 1 1

Fig. 4.177 Typlcnl noor plnn, Hongkong Dank Heodquorterr

i. Sect. 4.61 Condensed ReferencesIBibliography 339 1.


AlSC 1983. Modern Sfeel Corisrnlcrion 5 AlSC 1987. One Liberty Place-EBicirncy and Elegor!ce in file Cradle oJHirrary 2 Architeclun: 1988. Exploring Colnposhe Stnicrzdrer

Archilecture 1988. Tlso Union Squore Architeaurc 1990. High Sfrerrgfh Architccrure and Urbanism 1991. Two Union Squore

. ASCE 1986. Corrzplrrer 011s Tower Srecl ASCE 1990,Alrrrie Steel Aurtnlia Port Publ. 1988, Cltflej Sprrore on rhe Alo\,e Stnrclurer Building 1990. Do,,ble Srrcnpth Uuildisg Dctign 3nJ Cunrthction 1184. Outi,l8ng fkr,gr> anrl Cc,#.~ir..cr,'~.n Civil Encinccr 1187. Co,flcre,e Slrc,,~plb Herord Jurapr 3 V r . Concrclc Toddy 1989. A h ~ ~ o ~ ~ s Sorr8erhing Ne$u in Concrcle Conrtrnclion Specifier 1988. Innovative Comporire Conrrr~~rion Canrlruction Steel 1990, The A h y Facer of fhe Bond B,,ilding Drew 1990. Riulro Towers Prqiecz Seirniic Rcrpn,riu A,mlysir and E>,nlr,oriorl Engineering Ncwr Rccord 1988. S.vdncy Slycrnpcr Serr Soil Engineering News Record 1989. 19.000pri Enginecring Ncwa Record 1990, btnoi,ori!,c Tecbm'qlte> Engineering Ncwr Rccord 1991. Sydnry Toa,er Tertr A~lrfrolior~r Gcorgc 1990. Ii'ullirrgron'r IYiiid~Slirrped the C~~pirol', Tollert Bm,ilding Gillcrpie 1990. Derign and Co,zsrncrion oJSrn.1 Fronted High-Rire Blriidirrgs Grorrmnn 1985, 780 Third Atrenae, Tile Fin, High-Rirc Diagortolly Broccd Corrcrelc Sln,cf!8rc Grorsmnn 1986. Beliovior. Analysir orrd Corzrrr#ccriar~ ",fa Braced-Tube Conrrele Slrrrclt,ru Giosrmon 1989. Slender Smacnwes-Tlze Nc!v Edgc (10 Grorrman 1990. Sloider Carrcrere Sm,cfr,rrr-T18r New Edge Howillcur 1992, Dedgn oJrbeNorionr Bonk Corporufe Crnfcr Horc 1990. Srnrcrrrrol Design for rlre Riolro Towerr lloh 1991. 1Vind Rerisranr Derign oJo Toll Bl,ildi#tg ivi~ir m N l i p ~ ~ i d o l Crorr Seclion Journol o f Wind Engineering and lndurtriol Aerodynamics 1990. Oprinii.~afion oJToll Bltilding* Jor lVittd Loading

Kunemc 1985. Deep Coirron Fo~~ndofianrJor OUB Cerrlre. Singnpore Kuneme 1990. The OUB Centre Tower Folfndoria,rr. Sirtgopore Meinhvrdt 1981. S~8perrrrucrure Dc~ignJar llzc O\,rrreor U#iiorz Bonk B,,iiditcg. Si,,gll~lore Mcinhurdt 1990. Tire 008 Cmrre-Qnolig Deil>,eqs Melbourne 1985. Aerorlostic hlodel Tenr ovld Tl~eir Appiicorion jor rile OUB Ccrifre. Si8tgnporc Plnllcn 1986. Porrrtiodurn Engineering Plotten 1988. h f o ~ r ~ r ~ ~ r ! ~ ~ t l Plocr: Sleel Solvcr Co#!!plr.c Geon!vfricr Tnrnnth 1988. Sfrircf8~rnl Anolyrir orld Dcrigr! qfToll Baildir~gs

- .. * 7. - 5

Special Topics

5.1 DESIGNING TO REDUCE PERCEPTIBLE WIND-INDUCED MOTIONS

'She 3 ~ r ~ ~ c ~ u r ! l >!stem\ Sor la11 h.~il,Ii~~;, 3rd murc d l c n cun~r~>llcd I>> 11,c need 1 0 r:.lri<l rcspon.>e in sr ind nction ;)I ~ c r ~ i r u ~ h i l ~ t y Ic>cI\ 111:,n the nsu.1 tn pr,nidr. r<\ial.lo:? :,I ..I- l inulc lirnil-~1311: condilionr. This <eclioo $rill d?.ll \n?cif ic~Il \ ulllt illc c r , l cc~ ;~ r:1312d -~~~~~ . to human occupancy comfort and tbc design procedures uscd to eslnblislt the rcsponsc of a building to wind action and tlte sensitivity lo acrodynsmic shapc, damping, stirs- ness. moss, and mode shapc. Some mcntion will bc mademf implicalions to ullimale limit-stole design as snmcthing which tends to bc dealt rvilh niter the system has been designed to cope with the serviceability requirements.

1 Response and Excitation Mechanisms

T h e rcspnnsc of tall buildings ln winrl :tclinn can be cnnvenirntlv seoaretcd inlo alona- .- ~~~~~ ~ ~~~ , . - wind and cross-wind motion in relation to the two distincdy separale excitation mccha- nisms. The total response is, otcourse. a response lo both lhcsc motions superimposcd on each other, which results in a random. and somelimes r o u ~ h l v elliptic. motion o f the - . top of the building.

T h e along-wind responsc is made up oS a mean component and a fluctuating componenl. The addition of these two c o ~ n e n l ~ o r t p o " " n t lo the detcrminntion ofulliml?lf limit-state loads, but it is o n l y component s+~l~ich ~ i v c s rise lo accclcra- lions that affect occupancy comfort. For the cross-wind response, lhc meen componenl iEiZiXJy very small, with the fluctuating componenl dominaling the response. The fluctuating component of thc along-wind response is primarily driven by iluclualing prcs- surcs on the upstream Pace. which are caused by the fluctuating wind speeds in the inci- dent turbulent flow. Thesc pressure fluctuations are conrreried to along-wind response of lhc building through a combination o r quasi-steady response to low-rrcqucncy components and narrow-band resonant responsc, primarily in the first mode. The cross-wind fluctuating rcsponsc is primarily a narrow-band resonant response lo lllc fluctualin$ prcs- sures on the streemwisc s u r f ~ ~ c c s c:iused by the fluctuating vortices shed Into the a,akc. 11 is rcrerred to as \\sal;c crcilation where buildings sie conccrscd in order lo distinguisli il from the narrou.-band vortex excitation of slender slructurcs such as cl~imneys. The

342 Special Topics IChap. 5

mechanisms really are thc same. hut the broad-band nature of the cross-wind oressure fluctuations normilly associated with buildings is due to both the effects of fuibulence nnd the intermittent reattachment of the separated shear layers onto the streamwise faccs of the building. Typical along-wind and cross'wind response mccs and spectra are given in Fir. 5.1. which illustnter the resmnsc characteristics described.

L:ttr.r in rhts ;r.ctiun ;~n;~l)ticill mcthuds will be gi\cn to pcrmlt prediction o i the along-wind and cross-wind r~spnnscs. HouL.\.L.~. 10 permil soms further duscriptiun of titc fluctu:~ting con~poncnts that are in~portnnt to ~un.~ceabil i[y and olumnte limit-atatc considerations, it is helpful to refer to a diagrammatic reprcscntation of the along-wind and cross-wind forcinr soectra. as is nrcsented in Fie. 5.2. - . b

T2I1 huildtngs typically b3vc serr1ce3bility 2nd ullimate I1m1t.st3te operating value, o1r;ducr.d r.~.louit) in ihc range o f ? to 10 Fnr ea3lnple. a 3UU-m (98.1-it)-high hullding with a u,idth b of 50 m (164 II) 2nd fir.[-mode f rc~uencs !I ui0.15 Hz tnicl~t have scr- . . vicenbility and ultimotc limit-slate design mean wind speeds a1 the top o i t he building

along-wind

Fig.5.1 Dirploccmcnt IrurcsulUwlop ulnnncruclnsticmodcl olorquorc toner: hm = 7.

Sect. 5.11 . Designing to Reducs Perceptible Wind-Induced Motions 343

height of 26 and 45 mlsec (85.3 and 147.6 fdsec), respectively, which gives, for Ser- viceabilily.

and for the ultimate limit state,

With reference to Fig. 5.2 it can be seen that buildings operating in the low reduced- velocity range arc not likely to have occupancy comfort problems. At higher operattng

- Fig. 5.2 Along-wind and crurr-wind force rp~ctrn lor model squurc inner: I d = 7: I'h/nlr = 10.

346 Special Topics [Chap. 5

Plots of the acceleration criterion are given ns a function of frequency in Fig. 5.3 for a period of 10 min of maximum wind in a return period of R years. The period of I 0 min has been used both to fit in with the original curves of lrwin and of I S 0 6897, and because it is typical of n period of maximum response in areas dominated by thunderstorm activity and where mean design wind speeds tend to be worked backward artificially from peak wind-speed data. For regions where the maximum response may occur through longer periods, such as I hour, the maximum hourly mean wind speed will he less than the maximum 10-min mean wind speed, and the value of Tin Eqs. 5.5 and 5.8 would increase to 3600 sec.

3 Determination of Response

At the design stage estimates of the response of a building are required to determine serviceability nccelcration levels, equivalent static uitimale limil-slate base moments, and momcnt and shear force distributions. These estimales may be obtained analytically, from wind tunnel measurements, or from a combination oflhe two. The wind tunnel de- rivation of lhesc design data will be givcn elsewhere in this Monograph series. For this

frequency n , Hz

Fig. 5.3 Horizonlol ucrulcrntion criiorin for occu~oncy comfort in buildings.

01 forO.06cncl.O O . ~ < R ~ I O

ix -_.. .- - C

. .. 0 - ..-. .- . 1.-.

return period - .. . rn lo - . -. . .. . . -. 10 year 0, . - . . . - (U

- 5 0 D m .. ..

IS0 6897 (1984) Curve 1, . 0.5 . N .- - standard deviation r . horizontal acceleration

criteria lor 1 0 minutes 5 year in 5 year return period

- for a building (1.e. a,. exp (-3.65 - 0.41 Ln n)

Sect 5.11 Designing to Reduce Perceptible Wind-induced Motions 347

1

section, a dcscriplion of ihc snalyticsi approaches will be givcn, aibcit heavily cmpiri- cally supported in places.

approximately normally distributed response). 0 ,2

I 0.5

;llnnp-IIT,,d Rrponrc . 'I.he ~ ~ r t laclur a p p m ~ c l ~ ~ ~ O I I L . : I L . ~ 0) D ~ V S I I ~ O T I (19611 and Vickcr). (1966. 1969) prosides tlle simpl~.sl mc:tns of esiintalin: tllc llunf-wind re- soonrc o i :$ buildins sod the tqoivalcni riatic i o ~ d lo pruducd illc pe3k rslponrc. V?r-

I , , * , I 0.05 0.1 1.0

sions of this approach have been developed in a number of the \vorld's wind-loading codes. In particular, the Australian code AS1 170.2-1989 has a version in which nll tile parameters arc given in equation form.

As ihe gust factor approach is in such gcncral use, there is no need to develop it here. nnrticuiarlv as it rcleies io the determination of ullimate limit-state design data. How-

~~ ~- ever. so that comparisons may be m a d ~ bmwcen along-wind and cross-wind servicc- ability acccleralions, it will bc of help lo develop the along-wind equations here. The evaluation of i i ~ e along-wind response is divided into background and resonant response components. The background, or qunsi-stcady, response is at random and rclaiivciy low frcqnencics. It is !he narrow-band rcsonanl response component. which generates the majority of the ulo?g-wind acceleration at thc lop of s building. Using ihe gust factor npproach, ihc peak acceleraiion at the top o f a building for rcsonnncc in a fundamental beading modcmay be obtained from

wherc GtC, = gusl laclor for resonanl component; = g?(u,j@,, - M = mean base orsertu_ming momcnt: for a square building, it can be approxi-

mated by 0.6'11 p?z bh2 ill, = inenial base bending moment for unii displacement at top of building: for

constant density and linear mode shape. = '4 p bdlt' (2lIr1,)'

g = peak factor; for normally distributed process, = rt. = first-bendine-mode natural frequency; can be approximated by 46lh, "

where 11 is hCighl in meters (u,/iil,, = longitudinal lurbulence intensity at height h

T = oeriod under consideration, scc; usually 600 scc for accelcrniion criteria Ir = 'height of building b = width of building d = depth of building I:, = hourly mean wind spced at height - It

S = size factor; = i1[(1 + 3.5rr,ltll'h)(l + -1,1~bl?,)1 E = longitudinal turbulence spcczum; = 0.47Nl(2iN')"' N = reduced frequency; = I~L,/V, L. = measure of turbulence length scnlc; = 1000 (hliO)"lr

p = air density p, = building density

5 = critical damping ratio

Cmss-IVi,ld Response. One of the simplcsi ways of evaluating the cross-wind re-

sponse, involving all ihe important parametcis in the process of resonant response lo wake excitation, is to use a mode-generalized force spectrum approach proposed by


Suunders and Melbourne (1975). Tltc mclhod makes usc nf mcasurcd cross-wind dir- placement spectra to g iven mode-gcnemlizcd forcc rpcctrum (for the firs1 mode) n l

where $ ( , I ) = spectrum of cross-wind displaccmcnt a1 lop o i building I ! , , = first-mode frequency nr = mod;il mass

H'(ri) = mechanical admiliancc: = 111 I I - (rll,,,,)']'+4<'(riIr,,,)?] i = critical damping ratio

For n lincar mode. and if crcit:~tion by low ircquencic is sntall and ihc structural damping low so lhat tlteescitation bandwidth is large compared wilh the rcsonanl hand- amidth. thc stondz~rd deviation o i displeccment at the top 01 thc building m;,y bc s p p r u - irnated by

and the t and :~rd dc\,iation oioccclcr:~lion is g i w n by

The lorce spectrum may be espiciscd in coclficicnt lorm by

ll,,S,.~ll)

' r . ~ = (k4pT;61,)2 15.13)

where b = building beieht 6 = buiiding width normal to wind direction

?,r = mcon wind speed al top 01 building

Then in terms 01 this forcc spectrum coefficient the standard devintion of acceleration becomes

p7$7/z Ti=- -

.I,,, (5.14)

For an werage building densily p, and a lincvr modc. &he modal mass is

and thc pcak acceleration at the top o f the building due to cross-wind rcsponsc is given by -

Typical values of mode-ecncmlized cross-wind force socclmm cncffirirntr f m r n ~~~ - . . -

lundnmental mode 01 vibrntion that hns a linear modc are gjven in Fig. 5.4. Extension of llicsc data tu nonlineer modc slinpcs may be made conservativclv bv mult i~ivinr! bv . . . . - . a nlode-shape correciion factor Tor accelcmtion of (0.76 i 0.24k). as discussed in

Sect. 5.11 Designing to Reduce Perceptible Wind-Induced Motions 349

Holmes (1987). where k is lhe mode-sltape posver crponent from Lllc rcprescntalion o r the lundamcnlal modc shape by $,!, = ( ~ l h ) ~ .

, ., 't: * : 4 Parameter Sensitivity

Tlicre arc sevcrnl steps lo csn~nining paramcler sensitivity. First it is important to demonstntc that along-svind response is n relatively ntinor problem compared lo cross- wind response. Second it has to be shown that mode shape is important and that it is here that tlte slructural systcm can piny a significant part. Third !he real problem of cross- wind rcsponsc lias to be demonstrated along with its attendant parameter sensitivity.

square seclion, - chamlered or rounded corners

rough circular section, octagonal, hexagonal.


Il'orI.cdExo,nplc. The simplest way lo introduce a study or the relative significance of the response t)'pe and the \'arious parameters is by means o f a worked example. For this purpose considcr a lall building for a rclurn pcrind of I year lor rvhicl~

Ir = 300 m

b = r l = 5 0 m - l',, = 26 mlscc

p, = 200 kglm' -

(r,/ l'),, = 0. I ?

i = 0.01 (at scrviccability lcr,els)

and frctlucnuy st the lirrt mndu. 4 6

rr,, = - = 0.15 Hz I,

rcduccd velocity. - I'

1'" = 6 = 3.47

pcc~h factor ( I 0 oiin). -

s = V'l In 60Uu,, = 3.0

I . 1 1 i I Gust ~ J C ~ O I for resonant co~iiponcnt.

klean bnse-o\,crturning moment.

- I - 4 = 0.6 - plf,:bh'

2 = 1.095 X 10'' N-m

Inertial basr-hending moment lor a linear mode for unit displacement at the top,

I dl, = - p$rll!' (?nrr,,)'

3 = 13.32 X lo9 N-m

Peak nccclcrotion at the top of the building due to along-wind resonant response for a linear rnodc.

Sect. 5.11 Designing to Reduce Perceptible Wind-Induced Motions 351

2. Cmsr-~vind l.e.rl?ol!se. From Fig. 5.4.

C,, = 0.00 15

Peak accelcrntion at the top of the building due to cross-wind resonant response for a cantilever mode shape. u,ltcre I. = 1.5,

Y = -- (0.76 i 0.25I.) 4 pf '

= 0.14 mlsec'

= 14.3 mg

and for a linear mode. I. = 1.0,

It is noted h a t the acceleration criterion for occupancy comfort for the l-ycar rculrn period and iirst-mode frequency of0 .15 l - 1 ~ for I0 min is ublained from

Forthis worked example tltc along-wind acceleration is \$-ell inside this criterion, but the cross-wind accclcration, even with a lincnr mode, is abo\,c this criterion.

I. Along ivind i,erst,r cro.ss wind. In Fig. 5.2 it $$,as shown diagrammalically why the cross-wind nccelcrations dominate the oroblem or occuoancv comfort, but thc ~ ~ ~ - - ~- . . \\,orked example sho\vs tltot even for a reduced velocity of 3.17 the along-wind ac- cc lendon is about 30% of the cross-wind acceleration (3.9 versus 11.8 ms).

2. ,+lode shnpe. Adjustments of the mode shape in order to get nearer a linear mode shape, by using structural systems such as k bracing at Zome levels to gel facade columns to contribute morc to resisting motion, can make n signilicant difference. In the worked example, going from a cantilever mode shnpe. I. = 1.5, to a linear mods shnpe, I. = 1.0, redrrccd the peak accelerntion by 10% (from 14.3 to 12.8 mg). For a buildine on a reducina core or tube svstem. onlv with I. = 2.0, for example, ~ - - tlx p?n:!lty rslat!vc to ii I i n c ; ~ ~ ~ m d c \ I I : L ~ L O i 3 ;trutu~J 5'i.

3. Duntpi,ty. Thr. urors-bind a:cclur~tion !s apprd\lm3tcl! I I I \ L . ~ \ L . I ! JC~L.II.IIIII c)n the snu;lrc roul u l thc d ~ n t l l i n ~ . I t is 3ppruxiut31~. ~U;:IU,C th~.rl: is 2 d ~ n ~ p i u - . c ~ n l r i - . - . . bution from nerodvnamic damoinc. which is normallv ~ o s i l i v e and which then rc- . - . . Juzc, the r ~ r u r i ~ r ~ l d;lnlpinn Jcp~'aduo;c In this nurLr.d ? \ ~ m p l e . if tllu hui ld~ng Ih;id ;< rutninrcr.d rullircw ,truut.~r;il *!rtim :lnd d:lml>inpii~ *~.~riceahi l t l : I-.!.r.ls 111

= 0.015. the urtlrr-wind pcak : . C C C ~ C ~ ~ I L U I I f . 1 ~ 2 1111::.r fnllldc 1s~111l.l ~ L . L . U I I I - .


which would bring the acceleration lo willtin the occupancy comfort criterion of 11.8 mg.

4. Frcqeency, 6ttildirrx de!>sirv, beizhr and esidrb, and olrrrtfonr~ rlmne. The dcocn- . . . . dr.ncc u l cm.s-wind .1ccclur3lic1n un p;lramstcrh a h ~ c b dlr .c l ircqucr~cy :~tld modal mxs is quit: cnmp lc~ and has bcen ~liacusred and er3luatr.d in somu dutail h) \!el- b n ~ r n c 2nd Ch~.ung (19881 Thc cun~pliu:lliun is mxinlv cnucd hv !he i3c1 thxt C.. is very sensitive to planlorm shape and reduced velociiy, as shown in Fig. 5.4, anla anything which impacts on frequency similarly allecls rcduccd velocity on C,, Ex- amples orthc sensitivity 01 cross-wind acceleration lo building height, sspcct ratio, and planform shapc wcrc given in Melbourne and Cheung (1988) and arc rcpro- duced here as Fig. 5.5. From this study the overall conclusions with respect to parameter sensitivity errccts on cross-wind nccclcrations wcre as lollows: o. The accelcr;llion is not, ss onc might inlui l ivcly think, dcpcndcn~ dircclly on

height or aspect ratio hld, but rather on buildinc platform size. lndirecllv hciaht - . , - is imnlscd hecausc the wind rl>:?d is 3 (UIICI~OII 111 It~.igbt. HCIIUC rcI;t!\~.Iy .IL.~- dcr lhuildings wi l l h3vc Itifher 3cculerslirnr III~I SC,U>I hllilcl:ny\, h u ~ tllu impor- tan1 p.ranlr.l:rr bcrc 51Lt2plilr"rm >iru and 3 r c r ~ g ~ . d-n\it).-ill olller srurdr, ms*-

1 - square building, sharp corners I t -----

square building, chamfered corners (-0.1 b) a

-- rough circular, oclagonal

or tapered building

+=recommended

I criterion

building height, m

Fig.55 hlasimum shndord dcriulion urcclcmllll_n far I0 lnin In 5-scar rtlurn period for nrrluu rsnogumtiunr; 5 = 11.111; ps = I60 kg/m'; V,, = 12 (hNOOl"J'; n = 4611,.

Sect 5.21 Fire Protection of Structural Elements 353

b. Accrlcration is proporlional to lltc square root 01 the lorcc spectrum coellicicnt C,, and this is where paramclcr dependence bccomcs cnmplicaled. With reler- cnce to Fig. 5.1 it can bc noted lllat CFS, lo r a_fii.cn building gcamclry, is cx-

, ;pressed as a lunction nrreduccd velncily 1'" = V,lr,,b and that C,, increases wilh y >

V, up to a peak tltis range covers most applications. This implies an additional direct dcoendcnce on wind soeed. which makes thc accclcralion dcpendcnl on -~~ . somethink approaclling 10 over this region. Also thc increased size dcscribcd by building width 6 reduces V.. nnd llence C,:,, which also works to reduce acceleration in nddilinn to the n;bssivcncss clfict. Howcvcr, this size increase also moves to reduce frequency and hence increases V", and also C, and accelcration.

c. hlodest rounding or chnmlcring orcurners (10% 01 widdt) docs no1 significantly rc- ducc serviceability accclcralion lcvels, although a significant reduction in ultimate lirnil-state momcnls cun be achicvcd. More significant comer roundinc or chamlcr-

relative to that Tor a square, sharp-corncred building is rcasonsbly ochicvnble.

Ovcn l l the eliccts o r irequcncy, building density. l t c ig l~ l and \vidth, and planlorm shape are so inrerrclalcd that i t is nnly by the typc arcvaluation shown i n Fig. 5.5 that an appreciation or lhese aspects can bc uhtaincd.

5 Conclusions

The excitation mechanisms \\,lliclt csusc the most pcrccplible motions in tall buildings havc bccn dcscribcd. nnd il has bcen shown tIt;i~ thc cross-wind rcsponsc i s (he domi- n:mt cnusc of motion ocrccotion nroblclns

a pirameler scnsiliaity discussion, wilh worked examples, has been presented to give a desiener some indication 01 how lo avoid lhinh acccleration levels i n lol l buildings, and

b " - so avoid the need for auxiliary dnmping systems. In particular il was shown that very tall buildings arc not necessarily the most sensiliue in terms of occupancy comfort, but that souareTsham-cornered. hieh-aspccl-ratio tall buildincs are l ikely to have accclera- - . tion p;oblems an.d that thcsc can be avoidcd by using p l a k r m shapes with cul corners approaching n circular shape. tapering with height. increased mass, and structural systems which straighten up the first-mode shapc.

5.2 FIRE PROTECTION OF STRUCTURAL ELEMENTS

The slruclunl system adopted for a building. including lhc choice of construction materials, is ohcn strongly influenced by ihc fire resislencc requircmenls o f building rc€- ulations and codes. Although building code requirements with respect to l ire vary between countries, i t is gcncrally accepted that buildings should bc designed for the l imit svatc 01 fire to achieve tllc follor\,ing objectives:

1. Providc an nccepl.able level o f safety lo r ihc building occupants and limfighters.

2. The adjvccnt propcrty is not dnmugcd.


The level of safety offered to the occupants of a building in the cvent of a fire is a complex function of numerous factors, including:

I. The likely chnmctcristics of the fire 2. Thc likely behavior o f t h e occupants (whcthcr they are alert or asleep, their reac-

tions) 3. T h e likely pcrformnnce ofcompartmcntation with respect to rcsvicting the movc-

mcnt of smoke and flames

4. The likely pcrformonce of early \ \wning systems (if any) in notifying the occupants

5. The performance o f t h e sprinkler system ond smokc control systems (if any)

6. The response of thc firc brigade

All o i thcsc factors arc probabilistic by naturc and functions of time. Time is of the utmost imporlancc in designing buildings for firc safcty-it being important thnt suc- ccssful egress be achic\,cd bciorc conditions become untcneble in the fire compartment. A systematic approach to dcsigning buildings for fire mfety needs lo take into account all ofthcse factors from a probabilistic approach and lo recognize the importance oftime.

In contmst to such an approach, tllc regulatory rcquircmcnts with respect to fire safcty that have evol\~ed in many countries gcncrnlly represent an ad hoc and unsys- lcmatic approach to designing buildings for fire safcty. Buildings arc rcquircd to be dcsigned such that the structural mcmbrrs possess a ccrlain fire rcsistancc as dctcrmincd in accordance with the standard fire test-a test that generally bcnrs littlc relationship to real fires and takes no account o f t h e time for fire dc\,elopmcnt :!nd sprcnd. But it is a useful tcst in that it allows the fire rcsistancc of clcmcnts of construction to be n t c d on n relative basis. Littlc account is taken of the types ofacti\ ,itics taking place within the building, and generally little provision is made for the reduction of fire resistance requircmcnts due to the presence of other components of the fire safety system such as sprinklers, smokc detectors, and more cflicicnt egress provisions.

However, it is likely that in msny silustions the application of a systematic approach to assessing the fire saiety of buildings will allow a substantial reduction in the level of the fire resistance required for membcrs-without resulting in any decrease in fire saiety. T h e purpose of this section is lo consider how the structural form of buildings may be influenced by the need to design for fire safety. For a thorough consideration of fire snictv in tall buildinrs. scc Fire Sofen, irr Trill Btrildin~s (CTBUH. 19921. - , . ,. .

r11 the outist i t nr.r.d. to hc $l:,ted t l ~ t c o ~ i c r ? I ~ - i r ; t ~ l l ~ d buildings src. rc13tiv~Iy 111121- f?c t~ .d by r:qt#irr.m~.nls for <trucl~.r;ll nl:nlbi.rr lo lr~\r. ;! l c \ s l of fire rurist3nce. This is because the fire rcsistancc ofconcrcte members is usually relatively easily achieved by selectinn an aooronriatc levcl of cover La the reinforcement and a minimum size of . . . mr.nlhr.r. I'or alcel rtruct.,r:,. oo the alhsr lh2nd, rcr~siremcnts for rttembcrs to h a w hi:h?r lc\r.ls ol'fir: re\ist:ln;r. guncr;ill! I I ~ c ; ! ~ ~ l i i ~ t I I ~ C , ~ ~ S I * I I I ~ I , ~ be prutc;tc I o,ith fire- protective coverings such as sprayed insulation materials or board protection. and this can result in substnntiallv increased costs for thc stccl frame. It follows therefore that it 3s unl! in the c ; ~ uf .,~ecl-fr:.mr.d hu i l J inp ti1:11 thcrr. ;!r: rc;.l henelits tu be p i n e d by rr.11.luing o r diimin~ting l l x nedd for firi. prol<clioo ur 1I1c rlruuu1r;rl fr:rnle. As Ibcngar (1992) has smtcd.

It i i the requircnrcn~i Tor r~rucluiisl fire prolcction (and corrosion protection) that ha\,c inhibited !he usc of crprcsscd or visible cxlcrnrl rteclu,ork with lvll buildings. Cladding and curlrin \\,all ryslcmr llrvc evoivcd and h1iv.e been urcd la camoullvgc (he fire-protected steel. As the need for taller buildings 1 ~ 1 s grown, i t hidr became more important lo utilirc thc

Sect. 5.21 Fire Protection of Structural Elements 355

cilcrior ollhc hulldings ior lntcral lo3d reriatoncc. Utrlqus $1 slcnrr rurh nr ihc brncrd lube of the John Hanmck Center. Chirqo. the framed tube o i the \\'orld Tnde Ccnlcr. New York, nnd ihc bundled l ~ b r ryslrmuf the S c ~ r r Towur.Chic3go. hmceval\ud. Y c l ~ n 111 df

there clrcr ihc c r l r rn~ l membcrr hld lo he fircpmoied nud clld cvcn iho~gln romc stnlr- turd reprrren!urion on iltc focsdcr hlr been ochicvcd.

In the following, det,elop,nsnts nri5ing from the n w d to design buildings for firc wlety cconumically and ihc cffcct n i th i s on the chuice oistructurnl aystsm and iortn o i member consuuclion are reviewed. These developments vnry from innovative ways for desienine steel members to achieve the snecified levels of standard fire resistance as - - given in the building regulations, to designing mcmbcrs Tor "real" fire rcennrios, to a n- tional engineering approach to designing for fire safely which lakes into account all components of the firc safety system

1 Design of Building Structures to Satisfy Building Code Requirements

Over the years various innovative approaches have been developed in an nttempt to reduce o r eliminate the need for conventional fire-protective coatings for steel members, while at the same time satisfying the (usually high) lcvcls of standard fire resistance required by the rclcvant building code.

ll'oter-Filled Alember~. Around 4 0 buildings (IISI. 1993) have been constructed with tubular columns filled with walcr and with an appropriately designed circulation system to ensure that local overheating of the column does not occur and thnt there is a sufficient supply of water to absorb the energy nssociatcd with the required level of fire re- sismncc. A detailed design method has been available for many years (Bond. 19751. The 64-storv U.S. Steel Cornomtion headauarters in Pittsbureh incornorales watcr-filled ex- tcnorcolumos and is onc of thc tollcst buildings in rhc world uhcrc this ryitum lhns been oscd fur providing the requircd fire rcslstancc for the columns. \\';it<r cooling is inosl suitable for columns, although with the addition of water pumps to provide adequate circulation. the melhod can be used for tubular beams. For tall buildinss the columns must - be divided into zones to limit the buildup of pressure within the column. In general, it is true to say that the use of water filling to achieve the required standard of fire resistance for members has potential when exposed tubular steelwork is rcquircd from an architectural viewpoinl

Columns of &fired Concrete ond Steel. The range of composite steel and concrete columns shown in Fig. 5.6 has also been used widely to provide an allcrnative to steel columns coated with fire-nrotective coatines. Both the encased I sections and the con- - cri.1s.fillr.d tubular sr.ctiunr offer significant ad\antazus nit11 resptut to rapid cnnrtruc- (ton. Tubulnr columns o f l l r g ~ cross s:ctiun h i \ < hr.~.n used ior t.1i1 buildings (hlcFJmn. 1990; \Vsr.tt 2nd Bcnnrus. 1987: Watson and 0'Brir.n. 1990) ( r t e Fig. 5 7) The locn. lion of r~inforcement in these members sometimes "resents difficulties. and the use o l t~nrcinlorced uuncrcte is nftdn porsiblr., dcpcnding nn thr. ~ t o c L ~ n ~ . s r uf tilt cnlu!nn. llir l ewl o f lu;tJ ;,pplicd lo t h ~ ' cnlumn. 2nd the ccccntnclly ol' load. Tlw Jes ig l of ntl\ud concrete and steel members for firc resistance is the subject of numerous publications (O'Mengheretal.. 1993: British Steel. 1992; Kruppa et al.. 1990; ECCS. 1988: CTBUH. 1992).

Firc-Resistant Steels. Alternative "fire-resislant" stccls hove been developed (Maruoka c t a]., 1992: Assefpour-Derfuly e l al.. 1990; CTBUH. 1992) and promoted by


various steel companies, particularly rrom Japan. These slecls give somewhat superior mechanical properties under elevsred ternpenlure conditions compared with convcn- tional steels, although use of these steels w i l l not rcmorc the necessity Tor a firc-protective coating-a lesser thiclkness or fire protection w i l l need lo bc applied and ihc steels are generally more cxpcnsivc than conventional steels.

2 Des ign o f Building St ruc tures for "Real" F i re Scenar ios

"Reol" Fires ~,crrrrs Slnndord Fires. The previous section has dealt with the design of buildings where the members are required to have levels of fire rcsismncc as determined in accordance with the standard fire test (ISO, 1985). The time-temperature curve associntcd with lhc stnnd;~rd l ire test varies markedly compared with those associntcd with real fires (Fig. 5.8). Thir ntatter -'ill not be considered in detail hcrc exccpl to notc that this has bccn demonstrated by firc tests that hare bccn conductcd in various-size compartments having dirierent surrace linings, various qunnlitics o i rucl (nonnelly rcp- resented by timber and plastic cribs), and varying degrccs or \.cnlilation (Pcucrsson el al.. 19761. Othcr fire tests have been conducted with real furniture in small and, more recently. in large firc comporlmcnts (Thomas el nl.. 1992a). Based on compnrtmcnt tests conducted in room-size enclosures \vith thc firc load rcprcscnted by cribs. various cngi- neering models haw bccn dcvclopcd to prcdicl the temperature (and timc-tempcralure)

reinforcement

(8) Square Sleel Tubs wilh (b) Circular Slssl Tube with Concrete Filling Concrele Fillhg

(c) I-Section with Concrele (d) I-Section Encased in Concrsts Bstween Fiangss (Arbed Column)


Fig. 5.7 Furrst Ccntrc. Pcrllr, Aurlruli:~


condttions given n certain lr\,el of \'entilation and fire load (Pcttcrsson el al.. 1976). Through .uch testing it has been recognized that under cenain conditions, it is pos~ible lo reducc (or cvcn cli~ninnte) tile lcvrl of firc protsction rcquirud for slructural members.

Blriidinrs tviflt External Steelwork It has been shown C a w and O'Brien. 1981: ~~~ o~

Kr.~pp;l, 1981) thdt the locntion of sleelwork beyond or at the facode of the building. or such that it is pmly bhiuldcd from flames which ma). come frnm thc uindows i l l tltc event of a fire. will under certain ventilation conditions result in temperatures that are not sufficientlv hieh to reouire fire ~rotection of the steelwork. ~em~oeratures cxncri- . - ~.nucd 31 (or hcyond) the facade are generally considerably lower than those within the fire cotnpanmrnt. This fact has bccn dcmonstr~tcd by muanr of fire tcsu in compnn- menu where h e fire load has been generally represented by wood cribs and thc fire compartments have various degrees of vcntilntion.

This aooroach has rcSulted in the use of unorotected external steelwork in numcrous . . bu!ldings such 3s Bush Lunc Houac. Lundun (lZig. 5.9) (Brorzstti r.1 nl.. 1983). uhurc thc S I L . L . I ~ O ~ ~ forming the external lit tic^. is of relat!vcly s rn~ l l cross sr.ctiun 2nd cuulud by water.

The Hotel de Ins Anes tower in Bnrcclona. Spain (Fig. 5.101, is a very recent example of the use of unprotected external s tcelwok (lycngar, 1992). In this cnse the outer columns and the lateral bracing system arc located outside the building facade. Calcu- lations were perlormed using the mcthod given by Law and O'Bricn (1981). assuming n git~cn lire load in a hotel compartment and a reprcscntalivc Icvcl of ventilation. The calculated temperatures for the external steelwork wcre confirmed by mcnns of a lire

I I 4 I I

0 20 40 60 80 Time (min)

Sect. 5.21 Fire Protection of Structural Elements

Fig. 5.9 Exompic of use o f rratcr-fillcd tuba; nusln 1.usc 14eu.c. Landan. U.li.

Special Topics

Fig. 5.10 Hnlul dc Ins Artcs. Uorcelunn.Sguin.


lesL 11 is clear that In this case the regulatory authorities were prcparcd to acccpt t l~ i s ap. proach in licu of all members having to achieve the higher level o f l i r c rcsislancc re. q u k d by [he regulations.

Similar calculalions havc bccn uscd in Japan (Sakumoto e t al., 1992) lor high-rise buildings to permit the use of unprolecled "fire-resistnnt" steel al lhc lacsde.

Pnrki11i,,6 Gnrnges. The firc load and vcntilalion conditions associated with parking garages are well known. Opcn-deck parking garages ore generally dclined a s buildings that havc at least two onnosite sides onen lo nt least 50%. Firc lesls involvinc cars in

nrovidcd the structurul members are at least o l a ccrtein size-snd this size is n ~ c l wilh prlctical scctions uscd in parking gers~ger-lhc temperatures achieved will not lead to off-loading of lhc ~ l ~ c l u r o l members. Thus mullislory st~.ul parking gacrges wilhuut firc protccliun cladding arc pcrmiltcd in muny countries o r ihc world.

Tcsts have bccn conduclcd on closcd ourkin: rarancs nnd thnsc ryhich arc waniallv - - - open but do not comply \t*ith thc prcccding delinition ol' opcn dc~.k (Bennclts ct al.. 1989). Thc lcsts sho~vcd t l~a t lhe fire tcmpcrelurcs in partially open parking geragcs can bc equivalent to those lhst would be expcricnccd in a clrrscd gsiregc. which in turn arc l ~ i e l ~ e r th;m those lhar a,ill he acliiet,ed in onen-deck romars. In Auslralia. Ibr r;lr:trcs

- - ing g : ~ r u g ~ w ~ i t l h usprolcctcd slruclurai slecl.

dfixircd-Occrrpnng. flrrildi~~gs. The n l a t l ~ ~ ol mircd-ncuupuncy hsildings i h no\$, considcrcd. hlullislory buildings oltcn incorporate stories \ahich under ihu huilding rcgol;~. l i o n arc rer~uired to 11:lvc a more fire-resistanl l\,nc of utlnstructiun or il hichcr lcvui of

stories. For eramplc, in many countries where isolalcd open-deck parking psrnge!, are nermittcd to hc constructed in unnrotected slecl. Ibis \vould not be ncrmittcd i f the onen-

where numerous buildings havc now bccn permitted Lo hc constructed with unproteclrd steel parking levels below srlorics ofoff iccr and shops. Figures 5.11 and 5. I? shogr, osc such crumple, where {our le\,els of open-deck parking garage constructed from nnn- tireprooled stcclr\.ork sre locatcd below I?, stories of office accon~rnudation.

E.s.vcnlir?l nrrd A'or~csso~liol ~l lcmbers . Buildin. codes usunllv rcuuirc :ill members

been succrsful ly argued in o number of situations. For csample. the building shnwn in Fig. 5.13 is a high-rise building incorporating large-dian~cler cuncrctc-lillcd l u h e . conlpositc concrete floors. and a reinforced concrclc scrricc s113f1. Exlcrn:tl trusrcr spanning hctwccn thc calumns \\,ere provided to ensure adcrluntc lalcral load rchist:lnc~ under design ultimnlc wind forccs and adrquate lelcral stiffness endcr scrvicc wind loads. The architecl required the estcrnztl b r ; ~ c i n ~ lo hc o fc rnosed stcclivork. yet u~rdcr

argued on thc basis that in thc cslrcmc cvcnt ol' fire. thc prc*cncc ol'thc br;wing \vus not

364 Special Topics IChap. 5

Fig. 5.13 I'n,poarll llmcc building, Sydncg, Austruliix.

An illustration of the benefits that mav be achiewd by the approach described is if- . ... ~ ~ ~ ~

lu$trated try a relsarch program undcrt3ken to in\.esIip;llc nplior~s ar5o:i;lted N 11h 111~' rc- iurbi*t!!nc6tt uf n . I i - $ l u ~ . building. Thc building. shown in Fig. 5.14. incorpural+ :r

braced str.ci cors and ciosuly r l ~ x c d cxterior s1:r.l column* uhich cnmbinl: tvith stecl spandrel beams to form an cirekor tube structure. The K-braced core is connected to the exleribr tube by means of transfer trusses at the lop and midheight of the building. Bell rrusscs extending around the perimeter of the building are located at the top, midhcighl. and bottom of thc building. All of these steel members are fire protected by means of concrete encasement, which in the case of the exterior columns, is further encapsulaled



by 51ur.l plxe. In addition. thr. corc is sep~r:tt~.d from tile re51 of thc ares ofr.;ich $lor?. b! mjsunry <rallr. Thc floor b c ~ m r ;~nd cumpusill: noor sl3bs ore protecttd \rich asbss t~5 . hascd fire prateclion mntcri;il ;rs is the inside s u r i ~ c e of the fitcndc lbe3n1s.

The sprinkler system in the buildine does notcomnlv wilh currenl code renuiremcnts - . . for sprinkler hczd spacing or ua1r.r del iwry rdtcr. hlorcovcr. !to sprinklers arc lucnlcd in thr ceiltng .,pact, as is required for cununt construction.

lllc pr0pohr.d rclurbishmcn~ of the huilding required lhc rsmoeal uf;irbestnr-bared fire prolectiod material from the beams w h i c h s u n ~ o n the floor slabs and from the sof- . . fit u? lhc con lp~s i l c nnor slabs. For the refurbished bullding tu mr.r.1 1h2 dcctncd-tu- co!oplg requirtmc-nts of lhc regul:!lions, il rvould [squire respraying of (he bu:lms and floor sl:tb suffit, alteration of the sprinkler syslcm lo c l ~ a n g ~ . it frum nn c ~ l r j l i c l ~ t h~,.- ard system Lo an ordinary hazard ivslem. i n d the f i t t ineof snrinklcrs in the-ccilins - . spacer. In contr:tst. the bullding nwner prupuscd Ikll the refurhished bu~ldlng retain tlie c r~s t ing aprinklcr llcnds snd that thc slabs and floor I,i.-ms rcmnin unprutcctcd. Thc rs- Ii3b1lit! of thr. sprinkler s)ste,n a a s further improved by 111s inclusion of 8dJiteun:.l monitored vslvcs and a system lo cnablc weekly checking of the presence of water in the sprinkler pipes at every noor. . .

A! 111~. rc.quesl oltlau bulldlng uwncr, a series o f fire t?sts and ii risk i lssessn~en~ wcrt undenakr.n. The risk assessmr.nt sr;!r conduct~.d by sgslemalic~lly modcling tlts events thnl mi:ht fullun the nccJrrcn.'i. ur ;1 fire i n the bullding. 2nd by usinp 3 hlonte C;~rlu simulntion lo cvaluntc the probobilitv of outcomes which would lead to dcaths arnane the uc:up3nts o f l h c hullding. 'Thr: r i ~ k s~.,r.ssmunl rr.-r carried itut fur lwo (con:-ptu;!lj \ i ~ - ost~ons-tlli. bdllding dcaignud lu s311s1y 311 of the rnitlitnt~ll~ IL.qUIremctll5 0111~1: C J T ~ U I I I

budding rr.gulalions: 3nd 1111. p ropus~d r ~ . f u r h ~ ~ h r . d buildinp Ir du<crabcd. E;!clt uf the modcls of the buildinc accurn~e l~accounted for the lavout of the buildinr and thc sub- a)rlerns 3nd compnnsnts u i t l ~ c fire silfcly syste~n. \litn! uf IIIL. d:13 011 fir^. E I U N I ~ 2nd 1ltvr.lnpmunt. 5rnuk~. mnv?ntcnl. ;!nd :~lnrrn cues rr.quirr.,l fur Ilk: risk 35vrwl:nt camu frum 3n urtenairr. lest p rogr~n t (lhulnas ct 11.. 19923) iit which four fire le,l* sssru cun- ducted in a test building specially constructed lo simulate part of the protolype building.

The results o r t h e risk assessment showed that the risk to life safety in both buildings is low, but that the refurbished building is substantially safer than that salisfying the minimum requircmcnts of the regulntions. On the basis of these findings the building has been refurbished such that the existing sprinklers remain and no fire protection is applied to the steel beams or floor slabs. . .

Further testing and r~.rc=rclt is hcing unden;lkcn to provide thc b ~ r i s lor ;i more g a t - eralirud npprnxh to dulcrminitlg thc lcvsl oifirr. r3fcty offcrcd bv a huildinc b ~ w d ntl

a rational consideration of the factors described earlier. Clearlv ruch an anoroach has . . the potential to oficr subal~ntinl f l e \ ~ b i l ~ t y ni lh reipdct I" slmclural lorn,. ;l\ ~ h c influ- :ncr ol;,ll campnncnts u i t h e tire snfctg s!stem cart be t;lhcn into account.


Arrcfpour-Drrfuly 1990. Fire Rcsirrottl High Srrcngri, LLIII , Alloy Slrcls Beck 1991, Fire Sufeir S?rrerr?s Drrign Urittg Risk Arsrr.vrsenr A I o r i ~ l r - D e ~ ~ c l o p ~ ~ ~ e ~ ~ i ~ in AIII- I ~ i i "

Benneru 1985. Open-Deck Carpork Fire Turrr Benncus 1989. Firc 6, Carpork., Bond 1975. Fire artd Sic.el Co,~rm,crion: Il'nrcr Coolcd Holloa Colrrrrnis British Stcrl 1992. Derigr~ Alo~l,rol for Conrrcre Fiilcd Coiirrruir

Sect. 5.31 Condensed Referencee/Bibliography 367

Brolctti 1983. Fire Prolerrio,~ r fS lcci S!n,cnirer-ErornpIcr of Applicorionr Chen 1973, Hurnon Purccptio,~ Tltrtrhoidr lo Horizonral hlorioll CTBUH Group CL 1980. Toil Building Cn'rerio ond Looding CTBUH Cornmillee 8A 1992. Fire Sofsi). in Tnii Bzriidirrgs Ducnport 1967. Gtrir Looding Focrorr ECCS 1988. Coicuiarion of rhe Fire Rcrirrosce of Curtrrolly Loodcd Corr!posire Srrei-Cancrere

Col~mirzr fiposcd ro rite S~orrdard Fire Holrnei 1987. Mode Sltope Carrecrior~r for Dyeo,riic Rerpor!rc lo tl'in~d llSl 1993. Fire Errgincerir~g Design forsteel Srrucnrrer: Store ofrhe Arr Irwin 1986, Aloriorz in Toll Buildirlgr IS0 1985. Firc-Rcrirloncc Test$-Eiemrnrr of Br#ilding Corolnrcliol? lyengvr 1992. Holei de lor Ancr To$l.rr. Borceiona, Sl~airl Kruppv 1981. Fire-Rrrizroece oJExien~oi Sreei Coit,asls Krunnv 1990. Srriccrt~ral Fire Design . . Law 1981. Fire SaJcry of Errenrol Srerin'ork Mnmoku 1992. De$,eion,nrnr orxd Terr Rertritr ofSAl51OB-NFR Fire Rcsirnl,>r Sleul for Procrer rG . ~~~~

Gorrllle For ~ o r r . 18,; Jopon Heodq?mnerr Baiidirig McBcan 1990. Tize AIYER Cunrre. Adcioidc-A Core Snady hlelbournc 1977. Probubilir). Dirrribtrrior~r Arrocio~cd wirh rhc I\'i,'i,ld Loodiug of Slrilclsres hklboume I 980, hrorer nr,dReco,z~rne,~dorionr an Accrlerolio,l Crileria for Occ~lpuncy Carrforl in

Toll Slntcl,,r.ur hlclboumc 1988. Designing forScn~icc~1hIe Acederorio,zr in Toll Buiidirtgr hlelbournc 1991. Acccieroziortr and Carrfirl Crircriolor Dtriidi#igr O'Mcaehcr 1993. Bc1,osiosr of Co,,zporilc Colurr!nr in Firc Petlenson 1976. Fire E,lginrrring Design of S led Slnncrllrer Rccd 1971. I\'i!'i,ld htdr,ced Alolion mid Heaiatt Coaforl Sakumolo 1992. ilppiicorion offire-Resirronr Stcrl to o High-Rirc Building Saunderr 1975, Toil Rccro,8puiar Building Rmponre ro Crorr-ll'ind Gcilorion Thornus 1989, Fire in Mircd Occztponc). B~ildirlgs Thomas 1992n. Fire Tesrx of ritc 1.10 IViiiio,n Srreel Of lcc Buildblg Thomnr 1992b. T l ~ e Efccr ofFire on 140 IVilliom Srrcrr-A Risk Asrcrrrrlenr Vickcry 1966. 011 rlie Arsesrmenr of Wind Efecrr on Elonic Slri,crllrer Vickery 1969. Or, rhe Reliobiliq ofG,,rr LLIadi,zg Focrors Watson 1990, Tt,br,lar Contporhe C a l u m , ~ ~ ortd Tircir Deurloprnrnr in Atrsrroiio Wyctt 1987. Sirilcrrrroi Fire Etrginccrittg in Building Design-A Core S r ~ d y

5-c

Systems for the Future

A look at the future not only concludes this study of slate-of-the-an sWctures but also ooens the door for another monoeranh in this series. The subiect of unbuilt ~ro icc ts and - . . . futurs syslcms. a rich mix of \isiunary project* from around lhc norld, hls fascinsung poluntl=l for furthcr chplorallon and prcscntation in 2 rcpir;tle volume.

Thls fi1131 chapt~.r sill semc as 3 brief summap o f u hcrl: !;!I1 build~ng ,)slcms sccm to bc headed in the near. rather than distant. futurk. Several oroicct dcs&intions are ap- . . pendud 10 chis sccuon, which illuilr=tc aamc nf thcrc principd icndcoc~si. The projculs dcmonslralc lhc rich divcrrity ol ayalcms now an\ail:,hlc lo d:signcrs. They irL. ;!I1 recently designed unbuilt projects, utilizing systems discussed in earlier chapters,

Core and ostriggers)~srems: Miglin-Bcitler Tower. Chicago and Dearborn Ccntcr. Chicago

Trussed rube q1srem: Shimizu Super High Rise, Tokyo

Hybrid qsrems: Bank of the Southwest Tower, Houston

The rcasuns ll1111 these building> rtnl;iin unhuilt range from chxnglng cconnmic condition,. as in thc c;tss ofthe Hank of ihc SoutBu,esi, lo pro~ccts ihdt au,ail h m c i n y in a slow m;lrkcl. such as the Sllimizu Suncr Hiah Rise. In addition lo lhcir unbuilt ht3tUs. the" also share some features that i~lubuatc l&dencics in tall buildioc desien. These in- , ~ ~~ - - cludr ;~rchilectur;tl, slrucluml. as ucll 3s othur lcodcncies lhai point to ihc fulure.

Before discussing lhe fcatures nflhcsl: tutvsrs. 11 is uorlh munlioning une \isionnry projccl, of ihe type that might appear in a future monograph, as suggested. It has some feamres common la the other schemes presented in this chapter, extrapolated to a height significantly taller. Willinm LeMessurier has proposed a half-mile-high tower [850 m (2789 R)]. the Erewhon Center (Fig. 6.1) (Architectural Record, 1985). With a floor plan approximately the size of the Sears Tower or the World Trade Center it has usable floor arcas proven in existing tall buildings. The structunl systems for this tall building have more in common with the unbuilt projects of this chapter than the current record holders. The use of massive high-strength concrete columns on the exterior, cast composite with the structural steel frame, utilize the cost-effective strength and stiffness of concrete in compression. Bracing is employed both as a lateral resistance system and 3s a rravitv load transfer system to allow all load-bcarjne columns to pnrticipalc in the lat- eml rcs(s11ncL. fornpl i ium cfIiciency.Thc result Is a;ury rigid 1oir.r nil11 3 10-acc PC-

riod uf\ lhr .~lion, ulilizing convcn~ion;tl uonrtructlun i:chniq.te~.

k Sect. 6.21 Structural Tendencies 37 1 i

i 6.1 ARCHITECTURAL TENDENCIES i

And so what nre some of the current tendenc~es in tall buildine dcsien that can be ex- ~ ~

pcctcd to continuc in the lite twcntirth ccntury and inlo thc n e u ? n l&u is no sinflc architectural trend, as in the 1960s and 1970s. char damirlarrs the design of 1311 bujldings. There are, of course, buildings that utilize structure as part of the architectural expression. in the tmdition oioroiecls such as Chicaeo's John Hancock Tower. whereas other . . - building slructurcs, primmly f r o r rhc 1980s. defer to the architcctur.4 massing choscn mare in con,idcrntion of urb3n design issucs. Grcatcr use of mixcd s)slr.ms, alung with architectural wends toward utilizing the structural syslems as a form generator (along with urban desien). are blurrinr these earlier distinctions and creatine mnnv outions for - - - . the 1990s and beyond.

The Bank of the Southwest Tower exhibits the potential for the massing and nrchi- tectural expression to accent and reveal the structural rystcm. The massive composite columns rcduce in size with height, and the architect lakes advantage of the column locations and dimensions to shane the tower in n more dvnamic and soarine, exuression ~ - . thdn n aimplc prismatic form. The hliglin-Buitler Touer :!nd the De3rborn Ccntcr, utilizing a core 2nd outriggcr system. xhisve similar form;, but with difiercnt slenderness proportions and tops.

Thc Shimizu Suoer Hieh Rise is a tmsscd tube with some other similarities with Chicago's Hancock. They are both mixcd-use buildings, with offices below and residcn- tin1 floors ahove.This requires smaller flour plates in upper floors.The Hancock achic\.es this with a constantly slouine exterior truss~tube. whereas Sllimiru rotates the tube, re- wltina in smaller flo~rol&;with each rotation. These two nroiects illustrate the oonor- ~ . , . . ~unlty prcsr.ntcd hy ;tn exterior truss guomctry 3, the print3ry 5ourrr: of ;trchitsctur;~l ca- prcssion, uhilc 31 tltc s3me time adhering to an clficlcnt and rigid slructur;~l i!rtcm.

6.2 STRUCTURAL TENDENCIES

The systems for the tall buildings presented here all take full advantage of the mass. widih. and uotential efficiencies of the towers. The similarities among these building . system, illustntr., by rxxmplc, do ign idcas that work i n nt;ln! dilfcrcnt cuild~tiuns. Thc follu~ring lid sumrnnrtacs the\e common features:

Composite elements

Use of high-strength concrcte for supercolumns

Bracing or core walls for lnteral stiffness Use of active and passive damping systems Use of better analytical 1001s and testing facilities

' h e r s is a grsaler lsndency to mix systeslr 2nd mattrials t o d ~ y . purti;ularly uanci2le 3nd steel Cnmpnsllc ncel 2nd cuncretc floor ryitem, =re utili2uJ in sll of tlw projcclr ~h;!t lullon. in additinn to elficir.nt urr. uf mxcri31*, tht scltlshuril~p ":!turd .,I th2 r!i-

a m lends itself to the reouiremcnts for fast construction. The improvement of high-

extcnsibn, bending stiffness

372 Systems forthe Future [Chap. 6

The use of braced frames or shear walls, in lieu of moment resistant frames, is also evident. Thcsc systems are inherently more stiff, and therefore more economical in achieving drift and acceleration limits. Bracing and walls sre locally more limiting than framed tubes, particularly when bracinapcnemtes the insrior volume. But bracinn and . . - core ivallc also upun up other opportunities for flexibility An e~amplu of this is the e r . tsrior wall oihraccd lor\r.rs. $rhcrc column* nn). be njuch sn~allr.r ban llte massive sections required for framed tubes

;\nuther 3d\,anccmunt in the pcrlormsncc nltnll buildings is thc usc ofdamping ,),- Itmi. Activc dilmping r)alums u,er: lir.4 uscd in llte rulrolil of Boston's klancock building. 35 llcll :IS i l l orifinil design fc3lure in Sen York'r Cilicom Ccnlcr. Thc World Trade Center was one ofthe first to use pnssi\,e damping systems..~he use of these systems is becoming more common now, and indeed the Shimizu tower proposes an active damping system (HMD). The improvement in analyticsl tools, namely, more powerful computers at affordable prices, has made some of these aduancements possible. And impr~\~cments in testing facilities, both shaking tables and wind tunnels, have also aided the undcrslanding and usefulness of these systcms. Base isolation systems for earthquake motion, as well as tuned mass dalnpcrs for the control of wind nloucmcnts, arc now common dcsign consideretions. Other systems, such as active control of building structures with advanced microprocessors, are also being tested, and increasing use could be anticipated in the future.

6.3 OTHER TENDENCIES

Finally therc is mo\,cmcnt toward greater inlegration in thc design and construction process through information systems. Consideration of construction methods and syrterns, including prefabrication, modulnr construction. and robotics. is cllanging the traditional project delivery systems. Information systems for monitoring quality assurance during construction as well ns monitoring the long-term performance of buildings are also on the horizon, with the integration of mechanical. wnical lransportation and maintenance systems.

Project Descriptions 373


Miglin-Beitler Tower Chicago, :?. Illinois, USA

Architect

Svuctural engineer

Year of completion

Height from strcct to rool

Number of storics


Building use

Frame material

Typical floor liuc load

Basic wind velocity



Design acceleration


Type of structure


Footing type


Beam span Beam depth Beam spacing

Material

Slab

Columns


Spacing

Material

Cesar Pclli Associates Inc. with HKS Inc.

Thornlon-Tomasetti Engineers

Future

610 m (2000 ft)

141

I

Orlice

Concrete core, major columns, outrigger walls, steel floor beams, Vicrcndcel trusses

2.5 kPa (50 psf)

33 mlsec (73 mph) at 10 m (33 ft); 1 6 mlscc (I03 mph) at 610 m (2000 ft), 50-yr return 71 1 mm (28 in.) at l loth floor, 50-yr return 9 scc

23 mg peak. 10-yr return

1.5 to 2% serviceability ZC = 0.0012: horizontal force factor 1.33 Consrctc cur< linked hy concrete b-am5 to cight major perimcler concrcte columns

30-m (100-ft) silty and sand clay over dolomitic limestone bedrock

17.4-m (90-ft) deep. 2.1- to 3-m (6- 10 10- h)-diametcr caissons sockeled into rock

3.96 m (13 ft) 10.67 m (35 ft)

460 mm (18 in.) 3.05 m (10 rt)

Steel

69-mm (3.5-in.) normal-weight concrctc on 76-mm (3-in.) melal deck

I I by 2 m (36 by 6.5 ft)

18.6 m (61 it) 100-MPa (14.000-psi) concrete

374 Systems for the Future [Chap. 6

Core Concrca. 100 lo 70 MPa (14.000 to 10.000 psi)

Thickness at ground floor 914.460 mm (36. 18 in.)

The ~tructural system for the proposed 141-story 610-m (2000-Ft)-high Miglin-Beitler office building has been designed by the structural engineering firm Thornton- Tomasetti Engineers of New York City (Fig. 6.2). A simple and elegant integration of building form and function has emerged from close cooperation of architectural, stmc- mml, and development team mcmbers. The resulting cruciform tube scheme offers structural effieiency, superior dynamic behavior, ease of construction, and minimal in- trusion at leased office floors (Fie. 6.31. . - .

hlnjor objucti\cs ofthc structural design were to ~ch i evc speed and cconnmy uf conslruclion 2nd arold inlerior colutit~is in urdcr to intaximizc net rentable nrcl. This \ras achieved through a structuml concept bared on a C~c i fo rm (crosslike) tube which, in ulun, is similnrin anocarance to a ticLtac-toe board. The simulidtv ofthis structurel erid . . . . allous 5 t r u c l ~ r ~ l tlcmcnts for the rlendcr t<lncr to costisuc onintermpled frdm lhc but- ton1 ufti\d building 10 the inp.

'TBL. cn~clforrn tuhu structural syst:m consists oftlic iullo%ring S ~ A major compuncnt5:

I . A 19- by 19-m (62.5- by 62.5-11) concrete core with walls of varying thickness. Theintcriorcross walls of the corc arc gencmlly not penetrated with openings. This con- tributes significantly to the lateral stiffness.

2. Eight cascin-place concrctc fin columns located on the faces of the building, which extend up to 6 m (20 it) beyond the42.6- by 42.6-m (110- by 140-it) lonar footprint.

3. Eielit link beams canncctinc the four corners of the core lo the eieht fin columns u

31 e\c.ry llonr. 'These reinforced concrclc b:nm< arc hxunchud at both ends for incrcn,ed s t i f f r l :~~ :~nd rr..l.l;r.d in dcpth 31 m id rp~n to allow fctr p35b3fc 01 mcchnnacill ~ L I C I S . Linking the fin columns and cure cnoblur thc full uidtli uf thc h~l ld ine tu act i n r e rw- . - ine lsteral forces. In addition to link benms at each floor. sets of two-stam-dcco outrie- . . b

gcr walls 3rc lucntud at Ievcls Ib, 56. m d 91. Thtac outrigger aal lr <nlvauce the invr- actiorl betrracn ertcrlor fin culumns and the corc.

4. A conventional structural steel composite floor system with 460-mm (18-in.). deep rolled steel beams suaced at approrimatelv 3 m I10 ft) on center. A slab of 76-mm . . . . ( 3 - ~ n . ) - d r . s ~ l-mm (20-g;;uge) conuglud mctni deck 2nd 89 mm (3.5 in ) ofslnne cun- ir:le tupplne ipJtli betrvecn 111s bcarns. Tne ile:l floor syr1L.m ia rupporttd h> the m>t- in-place concrete elements.

5 . Exterior steel Vierendeel trusses consisting of the horizontal spandrels and two vertical columns at each of the 18.6-m (61-it)-wide faces on the four sides of the building between the fin columns. To eliminate stresses produced by creep and shrinkage hlrains in the concrete fin columns, theverticals in 1heVirrendeel arc provided with vertical slip connections. This has the added benefit of channeling all of the gravity loads on each of thc building faces out lo the fin columns to help eliminate uplift forces on the foundations.

Exterior steel Vicrendecl trusses are used to pick up each of thc four cantilevered corners of thc buildinn. Corner columns are eliminated. nrovid in~ for comer offices \%itll ondisturh:d tisa,s. Coone:tlon* herncen the stc:l Visrendeel iru*.us 2nd 1111: r u n - ;r:w fin co l~ ,nn \ :!re typi:311! itmple shr.:~r c<lnncclionl ahich minimirc co\ts 2nd ex-

~~ ~

pedilc erection.

6. A 183-nt (600-it)-lall steel-framed lo\r'er st the top of the building. This braced frame is to house observation levels, window washing, mechanical equipment rooms, and an ossortmcnt of broadcasting equipment.


A cruciform tube structure provides a safe, elegant, efficient, and consmctible solution to h e challenge of designing the world's tallest building, the Miglin-Beitler Tower. The proposed swc tun l solution combines the erection speed of concrete construction, the flexibility for future change and the efficiency for horizontal spans of a steel floor system, and the superior dynamic acceleration response of a composite latenl load re-

'

sisting slluctunl system.

Fig. 6 3 Ploor Iruming plnn; hliglin-Beitlcr Toner.


Dearborn Center Chicago, Illinois, USA

Ar$$ilect Stnicturul engineer Year of completion Height from smeel to roof

Number of stories Number of levels below ground Building use Frame material

Typical floor live load Basic wind velocity Maximum lnternl deflection Design fundamenlnl period Design nccelenlion Design damping Earthquake loading Type of smcture

Foundation conditions Fooling type Typical floor

Story height Beam span Beam depth Beam spacing Material Slab

Columns Size at ground floor Spacing Material

Core

Skidmore Owings and Memll

Skidmore Owings and Merrill

Proposal only 346 m (1 135 ft)

85 3 Office Concrete core, steel perimeter frame, steel outrigger trusses

2.5 kPa (50 psf) 34 d s e c (75 mph) H/500, 100-yr return period

7.9 sec 22 mg, 10.~1 return period 1.75% serviceability

Not applicable Concrete core, steel perimeter frames, steel outrigger and bell trusses 24.4 m (80 ft) of clay over bedrock Concrete caissons with steel liner

3.96 m (13 fl) 13.7 m (45 fl) 762 mm (30 in.)

3.05 m (10 ft) Steel, gnde 250 MPa (36 ksi) 63-mm (2.5-in.) lightweight concrete on 76-mm (3-in.) metal deck

914 by 610 mm (36 by 24 in.) 9.14 m (30 it) Steel. grade 350 MPa (50 ksi) Concrete shear walls. 760 mm (30 in.) thick at ground floor: slrenglh 49 MPa (7000 psi)

The project will consist of an equivalent 85-story oflicc tower with a total overall gross enclosed area of approximately 246,000 m' (2.6 million ftz) of which approximately 227,000 mz (2.4 million ft') is above gnde (Fig. 6.4).

The first five floors will cover an area approximately equivalent lo the site and will contain approximately 9270 mz (98,000 ft') of retail syucc on the ground floor. con-


Fig. 6.4 Dcnrl~orn Ccnlcr, CBicugo, Illinsis. (Pliorn il). Hcdriclz-Blcrring.)


course level, and second floor (Fig. 6.5). The omce lower will be located at the west end of the site. Figure 6.6 shows the outrigger tmss system used.

There will be three below-grade levels. The concourse level contains relail rcntnl space plus mecbanicnl, clcctrical, and building services arcas. The second and third lower lcvels will bc devoted primarily lo parking for 237 cars. but will also contain the main incoming electric and telephone services, employee facilities, and tenant areas.

A multilevel relail galleria will extend from thc concourse lcvcl up through the second floor and will interconnect with the Dearbom Street and State Street subway sla- lions at the concourse level. The retail levels will be linked by cscalalors within a slcy- lighted, stepped atrium space. Two additional pairs of escalators will connect the first. second, and fourth floors at the clcvalor core. Offices spaces on the third, founh, and fifih floors !+-ill open into the atrium.


Shear wall

iagonal lo bottom chord connections shall lev loose for approximately 360 days

++ Fig. 6.6 Outrigger truss; Dcnrborn Ccnler.


Bank of the Southwest Tower Houston, Texas, USA

Architect ..;-

Structurdl engineer

Year of completion

Hcighl from street lo roof

Number of slories

Number 01 levels below ground

Building use Frame rnalerinl


Basic wind velocity


Design fundamcnral period

Design ncceleration

Design damping

Earthquake loading

Type of structure

Foundation condilions

Fooling type

Typical floor S l o q height

Beam span

Beam depth Beam spacing hlatcrial

Slab

Columns

MurphyIJahn with Lloyd Jones Brewer Associates

LcMessurier Consultan& with Walter P. Moore and Associates

Never built

372 m (1222 ft)

82

4

Office and retail. Steel with concrete supercolumns

2.5 kPa (50 psO

47 mlscc (105 mph). 100-yr return

1167 mm (3.83 it). 100-yrrelurn

7. 6.75 scc horizontal: 7 scc torsion

22 mg pcak wilh T M D 40 mg without

1 to 1.2% scrviceebility: 3.5% with TMD: 1.5% ultimate Not applicable

9-sloq-high A-frame trusses spanning building between concrcle supercolumns

At lenst 76 m (250 ft) of very skirr clay 75-m (245-it)-wide octagonal mat. 4 to 1.8m (13 to 6 ft) thick. 17 m (56 11) below g n d e

3.96 m (13 ft)

14.2, 13.4, 11.6 m (46.75.43.92, 37.92 ft) 530.460.410 mm (21, 18. 16 in.)

3.05 rn ( I 0 11) Sae l . grade 350 MPa (50 ksi) 63-mm (2.5-in.) lightweight concretc on 50-mm (?-in.) metal deck

8 columns. 2.9 by 6 m (9.5 by 19.7 11). m- pered to 1.37 by 1.6 m (1.5 by 5.27 it) al roof: 70-MPa (10.000-psi) concrete at base Stccl. grsdc 250 nnd 350 MPn (36 and 50 ksi) supported on A-frame trusses

The tapered form of titis mixed-construction 372-m (1222-11)-high towcr. its pcakcd sculptured crown, and the slender spire to top it of1 recall the dramatic upward-reaching

382 Systems forthe Future [Chap. 6

skyscrapers of rhc 1930s (Fig. 6.7). The architects were chosen as a rcsull of a design competilion l~ r l d by the dcvclopcr. Unforlunately the Texas oil-based recession made it necessary to cancel the project after completion of the design developmenL Thc towcr contained an area of over 204.400 m' (2.2 million ft'). At ground level and below there were retail soace and oarkine in addition lo a erand lobby mace. The towcr was set di- -.- . ~~~ - ~ - - . . agonally an its downtown Houston site.

The tower was square wit11 sllnped corners to provide more officcs with comer windows. and tapered from 55 to 46 m (180 to 150 ft) square at lhc cighliclh noor. It rcsled on only cigh; large concrete columns, which diminished in cross &ion from the lop of the hmmdatinn mat to floor 80 (Fin. 6.8). ~..- ... . - .

The overall slruclural slenderness mlio oftllc tower was 8.0. based on 390 ml48.7 m (1279 ftl160 ft), the ratio of t l ~c lo\ver ltcigllt above the lop of the mat to the horizontal dimension center to center of the columns at that level.

The severe Houston wind climotc. the liieh slenderness ratio orlhc tou,cr. and its nar-

and stiffness, with the lenst cost premium over that rcquircd for gravity loads nnd minimal interference with architectural lavoul. Thc main structural frames were four stccl s u p c r ~ r ~ s c ~ . ta.n in c3cil ilir~ction. ahicll a m ? (tic c n t ~ h~ilding luxd n ~ t to tbc concr?I~. coIun~n\. The ,.lp:rlruuc\ h:,d Ji:lcon;!ls III :. cl,c\ron P : I I I ~ T I I 21 n i l t~-*~ory i,>tcr- tnls, uith 11~r;ront;ll t lr . , n t 1 l 1 ~ lo.trtll ~ n d rliuth >tory ufe3ch. TIIL. d i :~non~ls ~ n l y ;I"-

pcnred outsidc the central service corc fur four stories out of each nine-story modu.lc (Fig. 6.9).

The entire nonrspncc outside the corc was olher\r,ise column-free, with conventional composite stcel beates spanning from the corc to a pcrin~ctcr stccl girder. The 24.4-m (SO-ill-wide core w a s bridccd bv a eair of Vierendcel trusses. Thc cieht high-strennth

cause of vortex shedding, thc tower would have excessive wind forces nnd lateral accelerations unless its vibration ncriod \r,as limited lo above 7 sec. a lour value for so kill 3 i1ru;tJrc Esun .d tltot pcrtod. ths tuner nccup:~nts aoulJ L'\p?rlcnc: t n ~ l r sq~cn t dir. conlfurl ir.m uin,l-iod~ur.d nl.,tlun .A sp~'c!al sh#d\ N:I~ madr: to assera the :.ntount u l ndditiunnl d;lmpinfi 1h3t illr. i . ~ o ~ ~ d : ~ t ~ o n - m ~ t - ~ n i I i n~e r :~ t l on SIOUIJ provld? (i,pproxi. . . matelv 0.3%). In order LO reduce accelcralions to acceotable levels. a tuned mass damner $!,tern. of 3 lype vmil:lr lo t11a1 iltrt311<d in .Us$\ York'\ Citicnrp Center. wns to be In- c:.tud III lllc craiun o f t l ~ c torvcr :I[ 352 6 111 ( I 157 it) ;~bnse graund. The mass block s n s lo have o weight of about 386 tonnes (425 tons) and was designed to increase the towcr effective damping to at lenst 3.5%.


Fig. 1.7 U:lnk sr the Soutliwust Tosrcr. llourton. Tcus.

Composite col (typ) ' (Side vierendeel truss Corner vierendeel truss 1 (4 per floor) (8 per floor)

Fig. 6.9 Elrvntion; Bnnk orthe Southwest Towcr.

386 Systems for the Future

Shimizu Super High Rise lSSHl Tokyo, Japan

Architect Structural engineer Year or carnplclion Height from street to roof Numbcr of stories

Numbcr of levels bclow fruund

Building use

Frame ~natcrial Typical floor lit'c load

Basic wind velocity

Maximum lateral dcflcction

Design fundamental period Dcsifn accslrration

Design datnping E;irthquake loslding

Typ? of rtructurc

Fuundation conditions

Footing type

Typical floor Stury height

Bcnm span Bcom depth

Beam spacing

hlatcrial

Slab

Columns

Size ot ground floot

Spacing hlatcrinl

[Chap. 6

Sllimizu Corporation Shimizu Corporation Proposal

550 rn (1804 11) 121

6 Hotel, officcs, retail shops. balls. parking Stccl reinforced cnncrctc

1.8. 3 kPu (36. 60 psf)

45.5 mlscc (I02 mph) Hi300 (Ievcl I loading; Hi200 (Icvcl 2 loading)

6.0 scc 5 rng peak. I-yr return 0.6% ser\,iccability: 2% ultimolc

Sciscnic rcrpansc rztctor (1.05

Trussud tube nlegastructurc

160 m (525 rt) a f send Combination ofcontinuous \r,:!lls and pretensioned high-strength concrctr (PHC) piles

3.25 m (10 ft 8 in.) hotel; 4.3 m (14 ft I in.) office

27.4, 15.8 m (73 f t 6 in.. 51 it 10 in.)

1.2, 0.9 m (-17, 35 in.)

12.8.10.0 m (42 rt, 65 f t 7 in.)

Steel U-type steel deck i lightweight concrete, 155 mm (6 in.) thick

4.0 by 2.4 m (13 by 8 ft)

26.0. 12.8 m (85. 41 Ti) Stcel and concrete; HT60. F = 60 hlPa (8500 psi) Braced frame

Sleel, NT6O

I.? m (17 in.)


The SSH building is 550 rn (1801 it) tall with 121 stories above ground and six stories underground (Fig. 6.10). This design project was intended to confirm the feasibility of consmcting such a tall building in the earthquake- and typhoon-prone counvy of Japan by the end of this century based on the technologies available today ot Shimizu.

The SSH building rvns designed as a complex consisting of hotels, offices, and shops. The building areais 44.000 m' (474,000 f?) for a plot area of 90.000 m' (969.000 ft2). The total space of the SSH building is 754,000 m' (8.1 16,800 it2) and is divided into three zones along the height. A zone was designed to be squeezed through the top and

Fig. 6.10 Sitlmizu Supcr High Rise ISSII), Tok~o , Jnpnn


rotated by 45' against the lower zone. The bottom zone, zone 1, consisls of 43 stories with an average floor space of about 6200 m' (66,700 ft'). The middle zone. zone 2. consists of 37 stories with an average floor space of4800 rn' (51.700 it2). The top zone. zone 3. consists of 36 stories with an nveroee floor space of 2000 m'(21.500 it2). Zones 2 2nd 3 h a w qky lobb~es at thetr lowesl levcls. n t e sky lobbies are tlte lohhirs for shut- tle clesnmrr. They arc also dc\ignrd tin mucl the rcqlliremunt for cvacu~lion area, in thc evcnt of fire.

The critical desien loads for the SSH buildine were the seismic and wind loads. The - rdsponsc apectra lor far-field eanhqitakes u.it11 largc magniludes sxpscltd in tlic Tokyu area appenr lo hare clsar p s x k around 8 acc Considering !hew spcctrsl peaks. 3 m q a - structke svstem with a truss-tube mechanism was employcd lo i c ep the SSH buildinr stiff enoudh to have a fundamental natural oeriod ofaboui6 sec. Thi; shor t~er iod helor -~~~~

avoid a lock-in vibrall?n resulting from the \'onex shedding in serer* uindr. The sltore ofTok)o Bay co~nprises sort suil srmlo. To ovcrcolne the roft soil condi-

tions, special attention hasbccn paid to the foundation ryslem. The proposed foundvtion svstem consists of a circular cvlindrical wall of a diameter of 162 m 1531 it) with oiler ind diaphragm rvalls inside. T'he thickness of the cylindrical outer will is 4.'0 m (1'3 ft) in the upper portion. It reaches e depth of74.5 m (244 ft). This unique foundation system a ~ ~ d i s this supcrtall building t o be built on such soft soil

Srnrctttrol Sjrron. A! tile sliu on the shore o l tht Tok)n Rny nrea. apeutral compo- ocnls of ohnut8 scc m3) hc pronouni~d ill ths rcsponsL. spcctrn for i~r - f ie ld ?2nltq~:ihci uilh large n~agnitudcs. Thcrciorc IIIC n;itural period o i 8 iec shduld bc a\oldsd for the SSH lhuildir~g. Hosrever. B ~ I I I : ft~ndilmtntnl n:lturnl psrind is hct lo be lnngur than R wc. ;I lock-in tihriltion due lo strong wind may bccoms a big issuc.

Two strategies werc eslablished to overcome these problems. The first strategy was to achieve a fundamental natural ~ e r i o d ofsienificantlv less than 8 sec. The tareet nat- - - ural period was set at 6 sec. The second strategy was to select the configurntion of the building to minimize the wind loads, especially for the purpose of avoiding a lock-in vibration.

For the first strategy. the structural system selected is a megastructure with a truss tube with steel columns filled with hieh-sueneth concrete. This svsrem achieves enoueh - - = sliffn~.s, for tile SSH hullding to have n first n;itural period olappro.\i~nately 6 scc.

For the second str3tcgy. the optimum configurntion for the SSH building was suught u a i n ~ wind lunnul c\ocri~nr.nts. Tllrce rvsolutioos r\.ers a p ~ l ~ u d lo the bulldinc. Th: first . . resoiution was to cui the corners off the building so that the floor plan wouid become closer lo a round shape. The second was to reduce the plan wea in the upper zones. The third was to rotate each building zone by 15" with respect to the zone below. This combination effectively broadened the power spectra of wind loads so that lock-in vibration should bc unlikely to occur (Fig. 6.1 1). A perspective of the strnclural frame is shown in Fie. 6.12. ~ - -

Thc soil 21 tile hullding silt i, urpdci3lly suft. To 3rsurs muugh c3pxity undsr Illis snil uundition. ;I spcci:ll ioendation syatum has hcen ~~mplo)cd.'I'lic unique asp<ct ~ . i t l l ~ . foundation is a continuous circular cylindrical wall system which cresies animproved bearing stress distribution and reduces construction cost compared to a conucntional system. The continuous ouler \\,all reaches 74.5 m (221 ft) deep. The foundation has a mat slab 5.0 m (16 i t 4 in.) thick bctwecn -23.5 and -28.5 m (-77 and -93.5 it). From the mat slab to the end of the continuous rr.all, piles and diaphragm walls mere used to strengthen the soil contained in the continuous wall. This foundation of a circular cylindrical shape is considered lo be rigid enough as a whole.

The lhickness o f t l ~ e continuous wall is 4.0 m (13 ft) down to -28.5 m (-93.5 it). Beyond that depth, the lhickness of the !rsall is kepl at 3.2 m (10 ft 6 in.) to tllc bottom.


D e s i ~ n Crirerio. The design criteria for the SSH building against enrthquake and wind loads are as follows:

1. Under leilel I loods. The stresses of the slructural main frames should be smaller than the allowable stress. In principle, no uplift is allowed Tor the foundation.

9 2. Under level 2 loads. The stresses of the smctural main frames should be below

the level thnt can be considered to be elastic as a wholc. In addition, no harmful residual deformation due to the foundation movement should be allowed.

Level 1 loads are those that are likely to be experienced by the building during the service pcriod. Level 2 loads are those that can be considered to be the maximum credible loads at the building site.

3rd Zone (hotel) typical-floor plan

2nd Zone (oMce) typical-floor plan

" 1st Zone (olflce) typical-lloor plan

Fig. 6.11 Tgplcul nsnr plunr; SSH buildint!.

Fig. 6.12 Eluvutlss: SSH I~uildlng.

Sect. 6.41 Condensed References/Bibliography 391

I n addition to these design criteria, the discomfort of the tiuilding's occupants due lo the vibration was assessed for wind and earihauake loads ex~ecled l o occur once evew war . F n ~ r 11)hrid mnss dampers , l i h l D ~ ) $<ill be installed ;,I the lop of lo2 SSH building. Tnc weight ofeoch H 5 i D i s abuut?00 1onne5 (??.I Ions). Tuo HhlDs n f 100 tonncs ( I I ? Inns) h:nu :~lr~.ady been inrl;lllcd ill ;I j0 -s l00 bu~ldlng in 0s3L=. J a p ~ n .

6.4 CONDENSED REFERENCES/BISLIOGRAPHY

AlSC 1991. Tljr ll'nrld's To11r~t Deilding-Tlre hliglbzdcirlrr Tower Architculurdl Record 1985. Il'illio,n LcAlern,rirr'r Super-Tall Srrircrurcr ASCE 1991. Bz,ildi,~g Abnr to Dr ll'orld's Tollert ot 1.999f1 Engineered Concrclc StrucLurer 1990. TI,< lVorldZ 7bllcrr Bui;di,rg-Cl,icogn's Afiglin-Dcirlcr

)irt~.cr

Mia" 1993. Soil-Sintottre lrrrrracriou Eljrc!.~ on rkc 121-Siog. SSH Blrilrlbig \Vmabc 1993u. Sln,cn,ral Dcrigrt atldA8?ol?.~i:rir ofrlrr 121-Slory SSH Duildirrg \Vvtebc 1993b. Onurgbzg Needsfor Dnr,,ping ,lnga!orri,zg Sj.rlun,r Applicable lo Super Toll Btnildingr

Current Questions, Problems, and

Research Needs

I . What are the structural systems and building data Tor other significant high-rise buildings in Europe. South America, and Africa?

2. What is the appropriate way to classify tall building laternl load resisting systems? How are innovative and evolvine systems laced within the classification - . schun,s stlch lhnl cataloging and data cullcctiott oTstructur3l syslcnls can be con- tinuously upd3tcd ;lnd oT urc to the pr~crlcinr cnginctr!

3. How are structural schemes tailorcd to local geographic condilions to produce economical desirns?

I. Should lhcrc be a proiu.wun;~l c o n s e t ~ s ~ s rufardii~g the auccpt;~h~l~t) df lall huilding structures wit11 rcspcct to wniccnbilit) iswe? such as later:ll drllt. nnru vibration, occupant cornfori, and noor levelness?

5. What oossible structural forms for extra buildine suauorl such as auvcd towcrs - . . . . arc possible for ultra-1211 high-rise buildings'! Whnt arc tllc sociulugical, pl;lnning. and inlnintcnmcc implicatinnr lor soch buildings'! Whal h)slellls are unvi- sioned for the nert gcncmtion of tall buildings over 600 m (2000 TI) i n hcigllt'!

6. What unique problems are enconnlered when exposing lall building slructural Trnmes on the building perimeter? What are the solutions?

7. What are the structural systems Tor the future in arcas of high seismicity?

Nomenclature

GLOSSARY

A36. Structurul rleel with yield strength of 250 MPP (36.000 pri). per ASTM svmdrrd.

A572 grade 50. Strucarol steel with yield rtrength of 350 hlPo (50.000 psi). per ASTM stun- dard.

Acceleration. Rate of chongc i n vclocity us u building su%~ys due to wind or crnhquakr foiccs.

Al lowable stress design or work ing stress design. hfcthod o f proportioning stiuclurcs such that the computed elastic rtrerr does no1 cncecd I spccificd limiting strcrr.

Band beams. Widc, shullow bcrmr used to achirrc minimum rtructur8l floor dcpth. A typical size would be 350 mm (13.8 in.) deep by 1500 mm (59 in.) wide.

Basic w i n d velocity. Wind rpced uicd for design before adjusting for rhiclding. height, ctc. (urually the vrlocily 10 m (32.8 11) above ground i n smooth. lcrel terrain withoul significanl ah- rtruclionr).

Bay window. Window projecting from the wall between columns or buuierrcr.

Beam link. Bcam scgmcnl bctwccn bmccs. or bclu'een a brace ond u column.

Bent. Plant frnmcworli of bcnm or truss members that support a floor or roof ilnd ll le columns that support there members.

Braced frame. Usually u fnme which derives is rtnbilily primarily from 1NSS raian. h lo i t el- crncnu hove pinned ends and do no^ dcvelop bcnding resistance. (Thcsc fnme i usually develop minor bcnding farces.)

Building standard. Documcnt defining minimum standards for design.

Bundled lube. Slruclural s)slem in nhicn rira;hlr.l i r lnwd luhcs "re >n;o?r.d or lrt.:~.tled lo- ~ e ~ l l u r rn t h ~ ~ sorilmnn u.all$ UI -IIIIII~LIO.IT ! ~ h ? i :re CUII IO:~C~ $!!to 18ngle \\:II1. IIICTC~! f~ r i8ng cnmnr~zbll#!r tnf rtrc\\es 31 ihc inleridsc uf \a:h c o n l i n ~ ~ u . tuhc,. I n :t h,nJI;.I I.,h:. ~ n d i \ ~ J ~ : r l - - . ~ ~ r~~ ~~ 2 - tube elemenlr may be ierminutcd a1 any nppropriste lcvcl

Castellated beam. Bcvm fubricoted by culling Lhrough the web a f the hcsm with a profile burn- ing machine, reporating (he two halves, moving one half along the other until the "tceth" o f the cu.tellationr coincide. and lack weldinr the two hal$,cs toecthcr. Deeo "enelration Wcldinr is then - ~ - ~ ~ . . urcd to wcld both sidcs o f the \s,eb.

' -

Center length. Distance along one member bctx,ecn intersections of ccnlcrlinrs o f perpendicular members.

Central business district. Key commcrciol iarso inridc most modem U.S. cilics.

Central-services core. Zone of a high-rise building. often located cenlriilly in plan. where elc- mtars. svairs, toilets, and ien.iccs shofts arc loc~lcd. Core may be cnclascd by co,lcrcle m r l l i or eiecl framer with lightwcighl cladding.

396 Nomenclature

Chevron. In!,cned V i n appearance.

Code. Building code, o legal document providing design crilerin far buildings in a paniculvr jurisdiction.

coefficient of variation. Rolio o f the rtvndard drvindon to the meno of n nndom variable.

Concentrically braced frame. Frome i n which rcsislvnce lo lilteral load or frame instability ia provided by diagonal K o r other auxiliary system ofbncing.

Core. Ponion o i n building lhvl includes elevaton, sloin, mrchvnical rhafl, and toilets, oflcn centmlly located.

Creep. Slow limc-depcndcnl change in dimcnrionr of concrete undcr il sustained loiid, primarily i n thc dirccdon i n whicl> !he load iicL5: u dimcnsionlesr qurntity having un iu o f strain.

Damping. Dirsiporion o f energy for dynamic lauding.

Dapped girders. Girders (or bcbms) hw ing u notch ul one or both ends in the underside to accommodate u corbel support within the girder depth or to crcrle additional rpnce for air ducts m d h e like.

Dead load. Ac~ui i l weight o f rlrucluml clumcna. (This is a gmrity lodd.1

Differential. Difiercnce or change between two vulucs.

Doubler. Plate welded to or p i l r~ l l e l to a web or nilngc to add strength.

Drift. L i l t r n l displaccmcnt due to laterill force.

Ductil ity. Ahility o f il mnterb~l to ahsorb energy through defornlidtion without hilurc.

Eccentrically braced frame. Fiiamc i n which the ccntcriinc\ o f bracer air offset lrom !he paints ofintrrscctinn o f l h r crnturlinrs of bcami and columns.

Environmental loads. Lozids on a i t rucurr due to wind, mow, canhquakr, or tcnlpcraturc.

Facade. Puce, espcciillly thc piincipul elrvdtion. o f u building.

Factor o f safety. Rulio o f ,Ire u l~ imal r rrrrngxh (or yield point) a i 3 malcriol to ihc working alrers i l i umed i n derign (stress foctor orrarcty): or ratio ofthc ultimntc loud, momcnl. or slrcvr o f a structur;,l mrmbcr to thc ss'orking loild. moment, or shcar, respectively, assumed in design (load fuccor o f rarely).

Failure. Condition where o l imit itute is reached. This mzy or may not i n ~ o i r e collupsc ar other cvtvrtraphic occurrences.

Fin. Plate projecting from u member.

Flange moment connection. hlonlent connection in which the bcdm is connected to thc flange o f the column.

Floor area rat io IFARI. Spccilicd ratio o f permissible floor space lo lot arc*. in which the in- ducemenl lo reduce lot coverage is sn impoiiant componml. Thc bidsic ratio is frequently inodilicd by providing "bonus" or "prcn~ium" floor npiacc for rucl, aspects as ilrcadcs. \rlb;icks. und plrziiq. Also called ldor mr;,~.

Framed tube. Pciimetcr ccluiwlent tube consisling o f closcly rpacrd columns ilnd rpiindrclr.

Fundamental period. i ' r rm. l i> i i l~u fir\t 111c,.lu8ll %#hr:ll#.ln .i.l tl~l8l.l n;. .Tlw 1111,: lbli.18 iw 1111.

n ~ . ~ l d ~ s < l.) <.. ..! l i u i ~ l .i\ PCIII I :~~~ I I~ III:~\IIIII.~II J C I ~ L ' C ~ ~ U ~ on oilr - 8 1 1 ~ 111 ihc \:111;.11 111 11* - ,,Id#" "cfl~:,,~~,, *##, ,112 .%,,,CC .,\I< ..,,.I Ih.8.L 1.8 11,: f i r . , ;,g:,,n

Hat truss. Stiff structural irusswork exlending from cure to pcrirnelei a top o i building.

Hybrid bui lding frame. Fume conslruction uomposcd ofdificrent structural building matrriitlr. such us concrete and itccl.

L imi t states. Condition in which i! structure or a part ll%creof celrcs lo ful l i l l one o f i o funcriunr or to satisfy the cc~ndilionr fur a.lticl~ it 1v;s dcsigncd. Limit stales uiln br clasrilicd in t a n cate- gaiics: i I ) ttliirr~rrir l imit sttt~es, ur,rrcsponding to the inad-c:lrrying c ~ p l c i l ) of lhc rtructurc (safely

Glossary 397

ir urunlly rcluted to there typcs of limit slntc), and (2) rrn~iceobilir). l imi t slotcr, related to the criteria governing normal use of h e structure.

Limit-state derign. Design process thal involver identification of all potential modes olfailure (limit rtnter) and mainlnining an nccepxable level of safety ogvinst their occurrence. Thc safely

... level is usually erlubiished on n probabilistic bnsir.

.* , i o a d end resistance factor design. Design method i n which, a1 n chosen l imi t swte, loo* ef- feels and resistances are sepnntcly multipiicd by factors ihal uccount for h c inherent uncenainlies in the determinudon o f these quuntilier.

Load combinations. Loads likely to nct rimuiwneourly.

Load effects. Momcntr, shcuis, and vxiul forcer i n u membcr dce lo loads or other actions.

Load factors. Fuctors applied to o load to cxpresr probability of no1 being excccded; safety factors.

Longitudinal. Direction of the longer plan dimension.

Max imum load lul t imate load). Plvsric l imit load 'or rlability l imit load. ur defincd: also man- imum load-currying capocity of u rmcture under test.

Mean recurrence interval IMRII. Avcngr time betu,rcn occurrences o f n random rvriablc thnt exceed its M R I value. The probability ihat h e MRI value wi l l be exceeded i n any occurrence is l/MRI.

Meandering shear wall. Shear wall following m i r r rgu l x line i n plan. (No1 u rectilinear assemblage o f wnlli.)

Medium-rise building. Multistory building ncithcr punicularly high nor low: usuillly i n the mngc of 10 to ZO stories.

Modulartubas. Condguoua framed tubular struaurnl aysremr which % togcthcr to form u complete bundlcd tube structure.

Moment resisting frame. lnlcgivted syslcm of rmctuml elemcnu porrrrr ing cantinuily and hence capable o f resisting bending forcer. (Thcse fnmcr uruuily develop minor u i o l forcer.)

Mullion. Horizontill or vcnicul membcr of n window-wall orcunnin-wall system hrl is normally attached lo h e floor slab or benmr nnd ruppons thc glusr and/or elements o f a window widll. . . Neoprene. Synthetic rubber boring physical prapenier closely resembling those ofnarunl rub- bcr bur not requiring sulfur for vulcmizution. I t is made by polymerizing chloroprcncs. and the Int- ter is produced f iom vcctylene and hydrogen chloride.

Node. Point a1 which subsidiary puns originate or cenler.

Nominal load effect. Calculated using a nominal load. The nominnl load frequently is defined with rcierence to u probability level; for cxnmplc, 50-gmr mean rccunence intcwal wind speed ured i n cnlculuting wind load.

Nominal resistance. Calculated using nominal material and crass-iectionul propcnies nnd u m- tionnlly developed fomuln baed an on unalydc~l andlor expcrimcntnl model o f limit-swte behavior.

Outrigger. Stifirtructurul m r r work extending from core to perimeter or any point to distribute column loads betwccn them.

Outstanding. Projecting fiom main plunc.

P-delta effect. Secondary effect o f column arid loads and latcral deflection on momenu i n members.

Probabilistic design. Design mchod that explicitly utilizer probability theory i n thc safety checking procrrr.

Probability distribution. Marhematical law UIm describes the prohubility that a random vrri- able wi l l vssumeccmin valuer: either ilcumulotivedistribudon function (cdfl or aprobability dcn- r i ty iuncdon ir used.

Probability o f failure. Probability ha t thc l imit slate is exceeded or violated.

398 Nomenclature

Probability of survival. One minus the probability of failure.

Rack. To deform o rrclangle in shcvrby dispiilcingonc sidc latcmlly relalive to theopposite ride.

Rmistance. Maximum loud-c~nying capacity ns defined by a limit nille.

Resistance factor. Panial safety factor ro nccount far the probability ofunderrtrength of mule- rials or arucruml mrmbcrs.

Seismic. Penvining to cunhquukes.

Shearstud. Short mild-steel rod with flattened head, wcldcd to a steel mcmbcr. to tmnsfcrsheor force brtu,cen steel and runounding concrete.

Skewed. Not parallel or perpcndiculur.

Slab-typs high-rise building. Building in theshvpc ofo vcnicvl slnbsrvnding on the ground on i u ahon dimcniion.

Spandrel. Bcnm spanning between columns on the erlerior of u building.

Spandrel beam. Floor-lcucl berm in thc face of a building, urunlly iupponing the edges of the floor slabs.

Staggered truss system. S lnc l~ ia l r)rlecr, for .l b~ilding n ~ l h u!tbrir:d fr3mcr in "nu ulrcc. lion and fr.ui8cr bnced ill the other direr!inu hy s\c ui stor).-duep in,...:, rucgcrco in lar3tinn 31

lltcrnjtc fnrnrr on C\L.TY ~ l h ~ . r nnor of 1 1 8 ~ b.!ilding.

Stocky. Hcuvy and thick, compored of clemcnls u'ith low width-lo-thickncrs ratios.

Stressed skin. Masriul used for strength and stiifnerr in its own dune, as in u membnnc

Stub girder. Vicrendcel floor girder comprising the concrete floor as thc top chord, u wide- flange beam or column section os lhe bottom chord, with the chords connected by the floor bevmr end shon lengxhs of the floor beam (stubs1 fired in line with the bottom chord.

Table forms. Prefubricated beam and slab fonwork complete with venical props.

Tiebacks. Mechanical devices for rupponing sheeting, consisting of porttenrioncd rods ertmd- ing to anchor points in the soil surrounding the cxcnvution or to rack.

Transverse. Direction of b e rhoncr plan dimenrion.

Trussed tube system. Tubular system for tall buildings in which larernl iorces are resirled by tmBs uclion.

Tubs. Struclure with continuous perimeter fmme designed to act in a manner similar lo lhut of o hollow cylinder.

Tune. Adjurtcorefully.

Unclad. Not covered by facade.

Vierendeel action. Using n planar rccmngulnr giid of members working in flcrurc to act ui a lrurs for longer spans far loads in lhnt plonc.

W14. Nominally 356-mm (I-l-in.)-deep steel scction n'irh wide nungc or wide I shapc.

Web moment connection. Moment connection in which beam is connected to web of column.

SYMBOLS

L = critical damping ralio

P = air density p, = building density

uL = standard deviation of ncceleration in horizontal plane

Abbreviations 399

b = width of building normal to wind direction

C, = force spectrum coemcient

d = depth of building

E = longitudinal turbulence spectrum; = 0.47Nl(2+fl)"6

6 = peak factor; for normally disvibuted process. =

G = gust factor for resonant component. = g 2 ( r r ~ f i ~ e

h = height of building

H2(n) = mechnnical admittance; = I [ I - (nln,)']' + 4(2(nln,)'

Lh = measure of turbulence length scale; = 1000 (hll0)'"

nt = modal mass - M = mean base overturning moment; for a square building, can be upproxi-

mated by 0.6 (112)~T'bh'

M, = inertial bnse bending moment for unit displacement nt top of building; for

constant density and linear mode shape. = (l/3)pbdlt'(2irn0)'

n = frequency of oscilladon with an approximately nnrmnl disvibution - N =, reduced frequency: = nLhlV,

"0 = first-bending-mode natural frequency; can be approximated by 46/b,

where h is height in meters

R = return period, years 1

= size factor; = (1 + 3.5n,hlVh)(l + 4n,bl&)

= specmmm of cross-wind displacement at t ap of building

= longitudinal turbulence intensity at height h

= period under consideration, seconds: usually 600 sec for acceleration criteria

= hourly mean wind speed a t height h

ABBREVIATIONS

ACI

AISC

ASCE

ASTM

C B F

CCD

CTBUH

EBF ECCS

American Concrete Institute

American Institute of Steel Construction

American Society of Civil Engineers

American Society for Testing and Materials

Concentric braced frame

Chicago City datum


Eccentric braced frame

European Convention for Constructional Steelwork

Nomencla ture

Abbreviations for Units

Bm British thcmnl unil -C degree Celsiur (ccntigmds) cm' cubic centimeten cm centimeter "F degrec F~hrenhelr h foal S ~ " m gal gallon hp horrepowcr hr hour Imp British lmpsriol 8". inch 1 joule K kelvin kg liilogrvm kgf kilogmm-force kip 1000 pound force km kilometer kN kilonewlo" a kilopascal k kips per square inch

kW kilowan Ib pound Ibf pound force I pound mars MI meg&jojoule MPn megnpurcvl m mcler mi mile ml milliliter mm millimelcr MN meganewton N ncwlon OL ounce Po pnscvl psf pounds per square foot psi pounds per squnrc inch 'R degree Rankine rcc second slug 14.594 kg \V WBll yd yard

AISC. 1983 MODERN STEEL CONSTRUCTION. Americidn lnrtilurc of Stccl Conslmclion. Chicago. Ill..

2d Q u o n ~ r AISC. 1987

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Contributors .~ , 1 ,

The following is n lisl of those who have contributed their time and effort to mnke this volume possible. The names, affiliations, cities, and countries of each contributor are given.

Inn D. Bennelts, BHP Melbourne Laboratories, hlelhournc. Ausrralia Joseph Burns, LeMessuncr Consultants. Inc., Chicago. Ili!nois. USA Brian Cnvill. VSL Prcstrcssin~ (Aust) Pt). Ltd.. Sydncy, Austmlia Joseuh P. ~ o l a c o . CBM ~ne i i ee r s . ~ o u i t o n . ~ e n n s . USA - - - - = - ~ ~ ~ -

Henry J. ~ o w a n , ' ~ n i v e r s i i o f sydney, syd"ey. ~"s t ra l in P. H. Dnyawansa BHP Melbourne Laboratories. Melbourne, Australia James G. Forbes, Irwin Johnston and Partners. Sydney. Ausmiia Eiji Fukuzawa, Kajima Design. Tokyo, Japan Max B. Kilmister, Connell Wagner Consulting Engineers. Brisbane. Australia R y s n r d M. Kownlczyk, Department of Civil Engineering. University of Beira Interior.

Covilha. Porngal (former: Bialyslok University of Technology, Biaiyslak, Poland) Owen Martin, Connell Wagner Rnnkine and Hill. Sydney. Australin William Melbourne, Department of Mechanical Engineering, Monash University.

Melbourne, Australia Seiichi Murnmatsu, Kajima Design, Tokyo, Japan T. Okoshi, Nihon Sekkei, Tokyo. Jnpnn Ahmad Rahimian, The Office of hwin G. Cantor, New York, New York, USA Thomas Scarangello, Thomton-Tomasetti Engineers, New York, New York. USA Robert Sinn, Skidmore Owings and Menill, Chicago. Illinois. USA Richard Tomasetti, Thornton-Tomasetti Engineers. New York. New York. USA A. Ynmaki, Nihon Sekkei, Tokyo, Jnpnn

Buildina Index

Pictures of the buildings uppevr on the itnlicized pilges.

Atlantn. Georciu. United Stater: Chicuco. Illinois, United Stotcr (Conr): - Gcoria Pacific. 214.215.216.217-219.3W 10 South LoSdle Sweet. 208 -~~ -. ~ . . . . . ~ ~

Allnnlic City. New lesey. Uniled Shtes: Three R n t National PI-. I I Tnj Mnhnl Hotel. 17.94.95. g6,97.98 3 1 1 South Wncker Tower. 213

31 1 Wcrt Wuckcr Drive. 15.213 Two Prudential Plucc. 182.183. 184. 185

B8rcelonn. Spain: Water Tower Plocc. 113 Hatcl de 13s Aner. 276.277. 278. 279. 358.

360 Boston. Mnrachurenr. United States: Dullu$. Texas. United Swtrs:

Dewey SquvreTower. 35 ,236 ,237 Bank Onc Centcr. 24-1.1-15.246 lohn Huncock Building. 372 Fint lntcmational Building. 260.261.

Brirbane. Auruulia: 262-261 Ccnuvl One P l m . 47.48.19.50 Intefint Plaza. 301

Charlotte. Nonh Cumlino. Uniled Slates: Hvmamulsu City, Japan: Nations Bank Corporate Center, 241.242.243 ACT Towcr. 68.69.70-72

Chicogo, Illinois. United Smtes: Amoco Buildine. 203,204,205

Hong Kong: Bank of Chino Towcr. 199

John HuncockCenter. 268.Z69.270.355.370 337.338

NBCTowcr. 3 Bcnkofthe SoulhwestTower.369.371.381. I81 \Vest hlvdison Streel. 206.207.208.209 382,383,384,385 OneNonh Franklin. 15 Four Allen Cunter. 166,167.168. 169 Onterir Ccnter, 265.266.267 Two Shell Plau. 197 Quukcr Onls Tower. 2 Sears Tower. 202,280,181,182-284,355,

369 Kamogawa, lapan: 77 West Wacker Drive, 124,125, 126 Kvmogvwt GnndTowcr. 104,105. 106. 107

Kobe. Jupm: Kobe Commerce, Industry 8. Tnde Center.

85.86.87-89 Kobe Ponopiu Hotel. 73. 71.75.76

Kunlu Lumpur. Malaysia: Luth Building. 17.32.33.34-37

London. Englmd: Bush h e House. 358.359

Lor Angeles. California United Stoles: Figucroa nt Wilrhire. 162. !63. 16-4. 165 First Interrule World Center. 313,333,334

Mclhournc. Aurtmlin: Bourkc Place. 19.23.24.U. 45.46. 109 Cassulden Place. 117.128. 129.300 Mclboume Ccnlnl. 27.28.29-31. 109 140 William Succt. 365 Rialto Building. 285.286. 287-289 624 Bouike Slrect. 362, 363 Telecom Coiporute Building. 137.138. 139

Miami, Florida. United Stotei: CenTruslTomer.315.316.317-319

hlinneopolir.Minncsoto. United Stutes: First Bank Place. 3W. 323.321.325-329

New York. New YoiL United Sutcs: Camegie Hvll Tower. 293.2%. 295,296 CamegieMusic Hull. 293 Citicaip Center. 310.311.312-314.372 City Spire Building. 109. 145.146. 147-149,

296 Concordis Hotel. 296 Embassy Suites Hotel. 116.117, 118 450 Lexington Avenue. 220. 221-22.1 Gmnd Central Station. 220 Mvrriott hlvquis Ha~el. 17.90.91.92.93 Metiapolitan Towcr, I1 1.112. 113-1 15. 145.

296 PvliiceTheatie. 116, 118 Russian Tea Room. 793 780Third Avenue. 267.271.272.273-275 17 Stale SmcL 158, 139.160. 161 Trump Tower. 170-172

ng Index

New Yok. New York. United Stuter (Cotzr.1: World Tnde Ceacr. 194.196.355.369.372

06aynma. lupun: Sumitomo L ~ r e Inrumcc Building. 230, 231.

232-234 Osaka. Japan:

Lcvin21. 130.131. 132 Nunkoi Soulh Tower Hotel. 77. 78.79. 80 Tokyo Mnnne Building. 99.100, 101-103 World Trddc Center. 81.82.83.81

Perth. Auruulia: Fonert Ccmc.357

Philadelphia. Pennrylvmio. United Slates: hlcllon Bunk. 225.226.217-229 One Libeny Place. 140. 154.155. 5.56, 157 1650 Market Street. 143

- . Ovenear Union Bunk Ccnier. 300,302,303.

3M-309 Rvrncs Place. 30.1 SingopareTm?ury Building. 119.120, 121-123

Sydney. Au~uuIrd: Bond Building. 142 Chiflcy Tower. 150.151, 152. 153 proposed office building. 361

Tokyo. lapw: N6E Building. 290,291. 292

Shimizu Super High Rise. 369,371,386,387, 388-390

\Vellington, New Zealand: hlnjestic Building. 133. 134. 135. 136

(undetermined): Ereahon Center (proposed). 369.370

Name lndex

American Concrete Inrtimle. 147 Americnn Conrulting Engineers' Council. 169.

Asrclpour-Derfuly ct ul. 119901, 355 ASTM. I I Auslnlim code AS1 170.2 (19891.347 Aurlnlivn Consuuction Senicea. I27

Butc. Smun & McCuchean. 27 Bcllurchi. Piew. Inc.. 235 Bcnnetu et nl. (1985). 361 Bennets a ol. (1989). 361 Bofill. Ricnrdo. 124. 126 Bond (1975). 355 Bomhont and Ward Pry. Ltd.. 173 Boundary Lvyer Wind Tunnel. 254 Bnnncn. June. Associates inc.. 235

Consulting Engtnccja Cn~ncil oiTeh'rrur. 169.262 Council [on Tall Bu~ldinps]. 5. 6 Council on Tall B.lildingr (19ROJ. 363 Council onToll Building;. Gmup SC (19801. 1.6 Council on Toll Buildings (195'2). 354.355

DnemIhloore Panncnhip. The. 244 Dilvenpon (1967). 347 D~r,mpon. Alan. 254.314 de Prru. Grmrd. 285 DcSimone. Cbnplin. and Dobiyn. 116.158 DeStelono nnd Goctuch. 124 DeSafano and Ponncrs. 126 Dumont. Francis Xovier. 94

ECCS (1988). 355 Ellisor and Tanner Inc.. 166.260

Brennm. Becr. Goman Associates. 293 . . British Steel (1992). 355 Brouctti et al. (1983). 358 Falconer and Beedle (19841.6.7 Buildinr Center Firc Snlew and Protection Fenucsr. C. W.. and Arrocivter P. C.. 186 -

Committee. 103 Flnck nnd K u m Auslnlio. 150 Burgee. John. ArchitecE with Philip Johnson. Faster Associnter. 335

244 Fox and Fowle Arshitecu. I1 6

Comeran Chisholm and Nicol (Qld.) Ply. Ltd.. m . .-

Cantor. Irwin G.. Office o t 170.220. 225 CBM Engineers. Inc.. 162, 163. 182. 183.315.

316.323.332 CrrmuMPetcrka. 157 Chen and Robcmon (1973). 341-346 City Center Theatre. 147 Cohcn-Burreto-Mmhcnrr. Inc.. 124.206 Connell \\'ngncr. 27.43. 127. 129. 137

Horrell Archiacrs. 127 Hedrich-Blcrsing. 21 1.239.298.378 Hellmuth Obatr m d Korsabuum. inc.. 260 HI(S Inc.. 373 Holmes (1987). 349 HRH Construction. 314

Jucoby. Edward. 31 1

Kujimo Corpontion. 104 Kajimn Dcrign. 99. IM Kasturi, liijjas. As~ociales. 32 Khan (1966). 5 Khan. Fuzlur. 192 Kohn. Pedenm. Fox. 150.225 Kruppv(1981),358 Kfuppa et nl. (1990). 355 Kurokau'a, Kiiho. 27.47

Law ilnd O'Bricn (1981). 358 Lchlersuricr. William. 369 LeMesrurier Canrultunu. 119.310 Levy. Jcnnifcr. 91 Lindsey. Cbcrter. and Arrociatcr. 320

Name lndex

National Society of Prohrrionnl Enginccrr. 169 Notions Bonk, 242 NBBJ. 330 Nihon Sekkei Inc.. 68.290 Nikken Sekkei Ltd.. M). 73.77.81.85. 130.?30

O'Msaghcr ct ol. (1993). 355 O'Neill. 135

Paulur Sokolowrki and Sonar. Inc.. 94 Pel. I. M.. ond P m e n . 315.332 Pel Cobb Freed and Pamen. lnc.. 323 Prlli. Ccror, and Associates, 206.209.241.293,

373 Perbnr and Will Pnmecrhip. The. 203.238 Perrort Lyan Malhirron Pty. Ltd.. 137.285 Petlcrsson et ol. (1976). 356 Ponman. John. ArrociaBs. 90 Panopin Hotel Daign Office. 73

Ranhill Bcrsckutu. 32 Reed 119711.341-346

L lq J Joser Br:rr.r A~~ucis tcr . 166. 381 Roarn$on. Lellle E.. ondArrucijlc$, 196. 199 I.r,ehc Schla<$n,xo 2nd I l ~ c l l . I82 Ko:co Design P0nr .n . I h8

McBcan (1990). 355 Mackboii~eiDenrnaflVcdigcr, I I I Man. Nu Chun. and Arsociater. 247 Mvncini Duffy Asrocintea. 81 M'lnning and Associates. 133 Mmin. Albcn C.. 162 M~ruoka el 21. (1992). 355 Massachusctu Institute ofTechnology. 95. Maunsell Prv. Lld.. 47

Melbourne (1988). 345.316 Melbourne nnd Chcung (1988). 352 Melbourne ilnd Palmer (1992). 344 Milsubishi Estate. 68 Moore. Widllcr P.. and Arraciuter. lnc.. 241 MTS Syslemr Corporation. 311 Murphy J h n . 145. 151.381

Rorenthnl. Steve. 236 Roienwusser. RobeR Asrocintes P. C.. I 11.

112.145.116.271.272.293 Roth. Emery. nod Sons. 158,310 Rudeman. J m r r . Office of, 310

Sukumoto etnl. (1992). 361 Snunders and Melbourne (1975). 348 Schumun. Lichtenstrin. Clnrnnn and Efron, I I I Sean. Rocbuck and Compnny. 280 Seidler. H w . and Asrociaer. 39 Sevrud Arrociler, 186 Shidw and Asrociuter, 206. 209 Shimiru Carpontian. 386.387 Skidmore. Owingr &Memill. 2.3. 197.210,214.

220.265.268,271.276.279-281.297.377 Skillins Ward Mngnurion Barkshirr, Inc., 320,

321,330,331 Smith. Jcsr. 204 Squire Pholognphicr. 44. 138

Name Index 415

Stone. Edward Durrell. 203 U.S. Slcsl. 95.355 Svuctunl Engineen Associalion of Illinois, 240 University of Western Ontario. 254,314,322. Srubbinr. Hugh and Associates. 119. I20.310. 382

311 UneclSAA Pmnenhip. 302 Swnnkc Hnyden Conncll. 170

Vickery (1966. 1969). 347 Tmge. Kenzo. 302 Thomas ct ol. (1989). 361 Thornor ct nl. (1992n). 356.358.366 Wmr Buller and Arrociom. 133.135 Thornor a o1. (1992b). 363 Watson nnd O'Bn'en (19901.355 Thompson. Leonard. 334 Wcidlinger Asrocinter. 90.214.215.235 Thornton-Tomare6 Engineen. 150,154,373,374 Womlcy. David. 314 Tokyo Marine. 99 Wu. Gordon, and Asrocinter. 256 Travis Pmncn. 150 Wyctt and Bennctu (1987). 355

Subject Index ' 8

A-fmmc rmsrer. 381 accelrntian. 353

cn'lcrie 311-346.351.353 ncmlastic tesls. 322 oirn'ghh.311 ollsoncrele scheme. 243 along-wind force rpecug 343 along-wind response. 49.341.342.345.347.

350.351 mchonges. 19 arch. tied. 323 mbitecturnl exprcrrion. 279 architecruml tendencia. 371 nrmwhcod desicn. 186.187

bnlcony weight, 79 b u d beams, 138 h m s o l u m n join4 194 beam joint. 37 benmz.eomporile. 9 belled Enissons. 212.213 bolted joints. high-strength. 2M hx-1vm SVUEIUR. 109 . . boredrhenr wall rynemr. llO braced core spine. 162 braced fnme. 4.51.52.68. 73. 87.89.90.372

connections. 52 braced oerimeter tube. 310 . ~

bncedrteel core. 154.3W. 320 wilh ouuiggcs. 150. 166

brnced steel frame. 3W braced rleel SlrucNrC. 94 building code. 245. 353 building density. 352.353 building drib 157

building mponw. 346 build in^ awnv. 95 hundicd bm;d cart tuber. 158 bundled lmmed tuber. 280 h~ndlcd tube. 198. 2W. 290.299

behavior, 202

cnntilever efficiency. 198 canlilcverryswms. 195 cmti levcd bny windows. 175 cnnt i le"cdC0~. 49 cmtilevcd noor. 126122 cmtilcvcred ring barn. 139 cnntilcvcred rhcnr wall. I09 cnntilcved tube. 192.194 cmtilevered venicnl rmrrcr. 51 cmtilevering wind benm system. 177 cast on rilecanmete. 104 chevmn bracing. 332,334 chevmn portem, 382 chord memben. 14 circulnr concrete core. 92 sirculnr face. 152.316 circular shaped buildings. 32.256259 cladding. 61. 147.209, 212,237,298,354 clasrilicntion of systems. 2.5-7 column nonunifomity. 296 column m r f e n , 243.317.319 c o h m :

composite concnc-filled steel-lube. 127 gravity-designed. 58 high-strength conmele. 320 pilotis. 101 ding. 191

combined fnme. 77 comporlte action. 9 composite benmr. I2

design. I I

418 Subject Index

composite column sections. 356 composite floor, 13.208 comporite me~ol deck. 212 computer molysir. 3 W computer flooring. 150 computer modeling. lhree-dimensionul. 267 concenuic hnccd frdmc;. 51 cancenuicnlly bnced core. 164 concme:

choiceof, 113 core. 373.377

with outriggers. 186. I88 care tube. 206 encaTcments. 227

stcel fnmes. 230 high-smngh. 44,285.330.371 high-suenglh columns. 320 perimeter fnmcs. 285 porttenrioned. 19 precast pretensioncd. 17 schcmc. 251 ahcvrcorc. 124. 170 slab. 10 rpvndrcl beams. 97 tube. 272.293 (See also reinforced concrete)

connections. 57.110.282 dewilr. 54.55 typcr. 58

conrtruction: cycle. 275 time. 137.256.330

continuous walls. 386 core:

diagonally bnced. 85.297 fnmc. 95.98 K-bnccd. 365 m d outrigger systems. 14G144.369 and perimeter fnmr. 133 umsverscly bnced. 81 trinngulw. 320 (Sce olro shcw care)

core-alone system, 143 carmrion pmtection. 279,351 costs. 330 coupled shear walls. I I I c m h wollr. 223 creep. 147.287.304 crosr-wind force specuu. 313,348,349 crosi-wind responic. 49.311.342.345.347.

319.351

crou,n. 34. 162.206.241.381 crucifow-rhnped spine. 32.5 cruciform tube. 374.376 cunain wall. 27. 120.354 curvilinmr-rhapcd building. 330 cylindrical tower. 119

dnmped rtructurcs. 1. 115,3W damper plater. 106 dnmperr. viscoclarlic. 330 damping. 1l5.227.296.314.322.341.351.382

capabilities. 3 W ryrtcm. 69.372

drpprd girdrrr. I 2 dead loud. 157 d e ~ o n ~ u u ~ l i v i ~ t style. I dcflrctionr 274.275 design:

onowhead. 186. I87 competition, 382 criteria. 389 laad deflection. 179 problcmr. 147

diagonal bncing: core. 85.297 exterior tube. 271 fnmcr. I tube. 276

displnccment tnccs, 342 double tube design. 296 ductile moment f m c . 333 dynumicstiffnesr, 103

eunhquohe. 131. 165.330.333.388 londr. 109 resistonce. 104 resisting cnpocity. 85 rerpanre. 107 wares. 69

eccentric braced fnmc. 51.53 ccccnuic K bncing swaure. 60.65 economy. 369.374 electrified floor system. 262 elecwrlvg u,eldine. 282 ulc%lt$un. IUh. 249, 305. 312. 385. 390 cnc~wd-<!eel tnnrfcr trur,cs. 116 cnd framc. 95. 96. 98

excitation mechanirmr. 341 cxteriortube:

concrete-fnmed. 210 diagonally bnced. 271

facade: onhitecture. 196 dingonulimdon. 198 geomelrier;. 152 snwtoolh. 219

fin walk. 90 finite elcmen, nndyrir. 50 fire. 353.354 fire compmments. 356.358.361 fire pmtmtion. 4. 103.279.353-367

pmteclivc coatings. 355 fire mgulnlory requirements. 354 fire rcsirwnce. 354.355 fire safety design, 362 fire tests. 358.366 firepmafed rtructunl rtecl. 212 firer. time-tempcnture curve. 358 noor diaphngmr. 329 floor fnminr. 7. 1 l

plan. 168.208.299.376 floor plans (drawings), ?9.36.41,45.63.73.

75.79.83.88.107.121.132.148. 149.

Subject Index 419

quarter-circle. 158 floor plae. I ? floar wction. 36 floor slab. 9.318 floorryrlems, 2. 304

composite, 9 p m m r e d and porttenrioned, 15-26

~ O O E :

circulx. 32 long-spm. 16 open-web. 13 plank 93

footing plan.35 formwockrynemr. 1 10 foundation. 82.304.319.388

rynem. 141 fme- tmr r intcncling syrtems. 57.59 f m c d tubesystem. 192 fnmcr:

conccnuic bnced. 51

fnmes (Con!.): deformolion. 55 diagonally bmced. 1 ductile moment, 333 cccenuic bmccd. 51.53 elevntion. 71.72 perimeter diagonally bmced. 265 perimeter moment. 158. 160 perimeter rigid moment, 130 perimeter steel. 124. I86 rigid. 60.61.74.77.81.90 rigid perimeter. 94 X-bnccd. 279

fnmcu,ork. M. 76.80.84.87.98. 233.278 rnming plan. 123.218.224.227.264.273.283.

305.379 frequency. 352.353 rriction tests, I81 furniture. 356 luture systems. 369-372

gallcriu. 379 geotcchnicnl conrultanl. 34 gnrity-designed columns. 58 gn r i t y load. 5.56. 122, 200.270.312. 333 gust factor. 347

hnnging gwdenr. 92 high-ruenglh concrete. 1.44. 110. 127. 172.

Z55.3W. 330.371 high-suenglh bolted joints. 204 hollow corr plank;. 134 honeycomb dnmper plate. 108 honeycomb dnmper wall. 104.106.107 hurricane. 314 hybrid perimeter tube.214 hybrid steel. I hybrid immure. 116.271.272.307.308 hybrid systems. 4.3W302.369

infarmodon systems. 372 inlemntionnl style. 1

jerk. 344 joist girdcrr. 13. 14 jump-form system. 137

420 Subject Index Subject Index

loleml deflection. 237 lotcrdl load momcnu, 243 lateral load resistunce. 5-7.355

resirdngsystem. 101.215 lateral loads, 4 lnteml stiffness. 314 lvteml n,ind-resisting system. 168 live-laad deflection. 122 long-span floan. 16

massing. 371 mart. 335 marlcolumn. 312 materinlr. 5 meandering shear wall. 113. 1 I 4 mcchvnical ducu. I 2 mega ponvl fnmcs. 276 m c ~ x o l u m n Eyslcm. 221.222 mcgustructurc. 223.296 megumrres. 301 mctul deck. 9. 10 mixed conswction. 119 mixed-use. 265.268 made-generalized forcc sprcwm. 348.349 mode shape. 349.351 modemist style. I modes o f vibration. 103 moment frame. 73 moment-resisting frame. 4,5.51.53.55-58.99.

I01 moving farmwork ryrlemr. l I 0 mulliure complex. 276

neohistoricvl style. I

occupancy comfon. 95.341.341-346.351.353. 391

open views. 152 open-wch noor. 13 optimiution. 56. 140. 157 ourriggcrs:

beams. 172.300 and belt wncs . 377 benefiu. 141-143 drawbuck. 143. 144 hutmsr. 158. 160

ourriggen (Canr.): rupenlingonds. 156-157 systems. 1.4. 146144. 186.188. 369 mires, 297.380 wollr. 374

ovenuming moment, 140. 142

pmeterwnsi t iv i ty . 349 parking ganger. fire conditions. 361 ponial fnmed lube. 319 peak occelcntion. 345,348,350,351 pedmrrian bridge, I66 pcdesrrion tunnel. 166 perceived motion. 113 pcmrptible motions. 353 perimeter h d a g c r . 327 pcrimetcr column loyout, 317 pcrimeler concrete columnr. 373 ~crimeter diveonullv bmced frame. 265

perimeler moment frame. 158. I6U pcrimear punid lube. 315 pcrimcler rigid momenl framer. 130 perimeterring mrr. I21 perimcterrleel fmmcr. 124. 186 perimesrrube. 170.223.225.235.241.244

wilh bnmd core. 220 nnd core. 247 and inlemvl core. 256

piles. hi&-strenglh concrete. 386 pilotir column$. 101 planform rhapc. 352.353 p la l k f lwn . 93 p l m . 43. 102.173.299.321 pony w r r . 323 porunodem style. I posttensioned beam. 22 porttensioned cancme. 326

n 0 0 ~ . 15 pornensioned flot deb. 20 pornensioned systems. common. 17 possenrioninp, rconomicr of. 2&25 Pnn uurr . I 4 precost concrete ponel. 66.67 precart pretenrioncd concrete. 17 prerhoring method. 115 preruerred floors. 15 presmessed tendons, cultinp, 2+26

pmject descriptions, 27-50.66108 302-338

fnmed lubes. 203-259 lrusscd Nber 266299

ni lmod back. 220.238 nilwoyrmtion. 78 nliingcalumnr. 191 reclnimcd nren. 82.247 reinforced concrete:

comtruction. 192 cam. I41 fmmc;. 57 rmctuml system. 285

reinforcement dewilr. 31 residentid buildings. 17. I W rigid box. 192. 198. rigid fnme. 60.61.74.77.81.90 rigid perimeter fmme, 94 ring bcom. 139 risk ;rrscssmenl. 363.366

suwloolh facade. 219 scismicmn. 69 seismic load. 333,388,389 reirmic zone. 134.330. 332 ienritivity studies. 274 servicwbility requiremenu. 6.341 setback. 215 shenr core:

with ouoigg~r benmr. I 82 with o u r r i ~ e n . 173 (See o l ~ o core)

sheor f m e deformations. 192 shcnrlng. 196. 198

cfiecf I94 shear ounels. 267 . . s h r u wall rystemr.4. 109. 110,309

open tube. 147 shear wallr. 77. 110. 116.230.318.1

with ourriggcn, 145 shrinkage. 109. 147.287 skeleton. 307 sky lobbies. 388 slender aspect rdtio. 271 slender buildings. 352 slenderswcture. 113. 145.296 slendrmerr mdo. 53.382 slip-formed concrete core. 43.92 slipjoint. I80

. 11 1-139. sloped colu4n ryrtem. 229 slopingsiIe. 256 spandrel beam dcmil. 97 spandrel uniu. 216 specin1 moment mist ing h e s , 57 spine suncurer. I. 1M. 165.323

' spire. 381 sp r iden . 366 aquare be. 198

IWCNre. 230 staggered uuer ryrtem. 95 st*]:

cantilevered floor bcnmr. 119 dcck 3 M fire-reriiwnf 355 framed mrr rmcture. 223 haming. 156 fmingryr tem. 129 higb-yield rwctuml. 301.308 mast. 335 open webjoirn. 13.14 perimeter fmmcd tubc. 166 perimeter frdmes. 150, 377 perimelerrube. 206,210

rteclwoik, crtemal. 358 alep buck. 162 stepped beam soffit. 24 stiffness. 12.109,296.3W, 341 ~tresling. 42 rvucrunl andyris, high-temperature. 279 r m c t u d plan. 70.292 r m d v r a l ~ k e l f l ~ r f n m i n e . 122 structural stecl scheme. 250 s W F N ~ ~ tendencies. 371 rmIIt ie mr. 178 rtubgirdersyatem. 12. 262 stud rhcorconnecton. 95 subsystems. 7 rupeicolumns. 116.3W.323.325. 326.371 supilrurr. 229 suspension mrres. 335

172 sway o f building. 82. 113

tall building, definition. 5 Wllc5t building. 280.376 wndem elevntan. 260 tapered girders. 12 tcndons. 21. 139 thin-wnlled concrete-filled tubes. 129 three-dimeniionol ncxion. 287 three-dimrruionul computer model. 153

. . 422 Subject Index - time h k ~ r y unolysis, 334. .1 vnlue engineering. 245

. top-down canrtruction. 188.335 ; vmicill conliirver. 192, 194,282 torsional louding. 109 ; vcnicsl trurrm. 52

loaionol mhlti?n. 328 : vibrations. 13 toniond stability. 325 3 modcr of, 103 m r f c r f l b o r p i n h 318- Vierendeel bandages. 313,325 m r h r rwmu&. 240, girder bundogrr. 326 m r v e n e l y bmced corc. 81 Vicrendeel benm. 192 me elemenu. 194 ., Vierendeel fnmer. 93.239 me-type construction. 299 Vierendeel mort. 337 w r . 203 .. . Vierendeel panel. 14.95 vinngulvrcom. 320 Vierendeel system. 335 vinnguiar rhupc. 39 Vierendeel truss. 223.2-16.262.374 triongulnr rile. 186 pipe trusrcs. 325 Irinngulnr lower, 11 1.30-1 vircoelvrtic dnmpen. 330 vinngulur lube. 198 voncx shedding. 113. 119.226.382 mr red abe. 196.260.371

' . systems. 197.369 ~ l l c s , 215.30-1.313 wuming syrterns. 354

comporilefloor. 14. 15. 16 warping-restmining bandugcr. 328 pony. 323 Warren Irurr. 14 P m t ~ 14 wcb diagonals. I 4

lube: wclded girder srubr. 236 concrete. 293 welding. tillel. 237 concrete-filled rlcel. 300 wind. 6. 109 divgannnly brdced. 171.276 wind beam joinl. 181 double lube design. 296 wind heumr. 179 exterior. 210 wind bracing. 263 pnniul rmmed. 319 wind engineering. 330 perimeter fmmed. 47.85,203.238.268,297 wind forces, 313 perimeter pnniul. 315 wind induced motions. 4,311,382 side-by-ride. 293 windload.49.82.121.131.249.273.287.388. ruucture. 168 389 surpenrion. 335 wind motion. 334 triangular. 198 wind ovenuming forces. 313 venicol. 52 wind reairloncc. 29 Vierendeel pipe, 3% eiemenu. 330 Warren. 14 syrlem. 157 water-filled. 355,359 wind response. 349

obr-in-tube. 27.32,39.-13.85. 137 wind rhenr. 254.313 tubulorconcepr. 304 wind-shedding farm 299 lubularefticiency. ?0i wind sway. 57 hlbulursyslemr. 1.4.5.143, 192-202 wind tunnel less. 49.68.75, 103. 113. 131, tuned morr dompcr. 153.314 133.146. 157.160. 166. 175,?26,217. tunnels. 129 . 254.273.274.287.314.322. 388 typhoon wind ciimae. 254 :

r @bmced lube, 274

X-bmccd frumer. 279 X-bmcing. 51,260,270

structural system for tall buildings(1)

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s t o c

r o b c

o r r internulional

kuwait consolidnted

o n office o f irwin

g c o r g

mnrl o t e p