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American Concrete Institute Always advancing

First Printing September 2018

ISBN: 978-1-64195-027-5

Code Requirements for the Design of Precast Concrete Diaphragms for Earthquake Motions (ACI SSO.SM-18) and Commentary

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ACI 550.5M-18

Code Requirements for the Design of Precast

Concrete Diaphragms for Earthquake Motions

(ACI 550.5M-18) and Commentary

An AC I Standard

Reported by Joint ACI-ASCE Committee 550

Larbi M. Sermour*, Chair

Suzarme Aultman

Roger J_ Becker*

le-Lin Chung

Ned M. Cleland*

Manuel Conde Fuentes

Thomas J. D' Arcy* William K. Doughty

Semeh Ibrahim El Ashri

Alvin C. Ericson

Mostafa Mohamed Gad Alia

Harry A. Gleich

Ne-il M. Hawkinst Augusto H. Holmberg

L. S. Paul Johal

Jason J. Krohn*

Emily B. Lorenz

*Diaphragm Subcommittee members who developed this code !Diaphragm Subcommittee Chair

Lance Osbome, Secretary

Kenneth A. Luttrell

Vilas S. Mujumdar Clay J. ·aito*

Clifford R. Ohlwiler

Victor F. Pizano-'l110men Charles L. Pizzano

Jose I. Restrepo* Sami II. Rizkalla

Mario E. Rodriguez•

Joseph C. Sanders*

James Schroder

John F. Stanton P. Jeffrey Wang

Cloyd E. Wamcs

Michael H. Weber

Special thanks to S. K. Ghosh and S. Nakaki for their contributions to tllis standard.

This standanl describes code requirements for the design of precast

concrete diaphragms subject to earthquake motions where used

under the design pmvisions of,-lSCESEI 7-16 Section 12.10.3 and A.CJ 318.\f The response of precast concrete diaphragms under earthquake motions depends primati/y on the strength, stiffness,

and defor711ation capacities of the connectors and the reinforcement at joints between the precasl concrete members. The seismic

forces specified in ASCEISEI 7 for the design of precast concrete diaphragms, their chonis, and collectors in stmctures assigned to

Seismic Design Categ01y (SDC) C, D. E. or F are tied ro force reduction factors specified in ASCEISEJ 7-16 Chapter 12, and to

ACI Committee Reports, Guides, and Conunentaries are intended for guidance in plamung, designing, executing, and inspecting construction. Tllis document is intended for the use of individuals who are competent to evaluate the significance and limitations of its content and rcconunendations 1md who will accept responsibility lor the application of the material .it contains. TI1e American Concrete Institute disclaims any and all responsibility for the stated principles. The Institute shall not be liable for any loss or damage arising therefrom.

Reference to this docm11ent shall not be made in contract documents. If items found in this document are desired by the Architect/Engineer to be a part of the contract doctunents, U1ey shall be restated in mandatory language for incorporation by the Architect/Engineer.

the shear overstrength provided by the connections and the rein

forcement at joints specified in ASCE!SEJ 7-16 Chapter 14. The shear overstnmgth depends on the design methodology, elastic or

ductile, used for the diaphragn1 and targets elastic response for

the maximum considered eanhquake for shear connections regardless of the design option selected. The design option rhat can be used depend� on the assigned design categ01-y and on the span and

aspect ratio of the diaphragm. The selection of the design option is

associated with minimum requirements for the tensile deformation

capacity of the connections and the reinforcement at joints.

Keywords: connections; diaphragms; earthquake-resistant structures; precast concrete; seismic design.

ACI 550.5M-18 was adopted August 13, 2018, and published September 2018. Copynght Cl 20 18, American Concrete Institute. All rights reserved including rights of reproduction and use in any form or by any

means, including the making of copies by any photo process, or by electronic or mechanical device, printed, written, or oral. or recording for sound or visual reproduction or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors.

2 DESIGN OF PRECAST CONCRETE DIAPHRAGMS FOR EARTHQUAKE MOTIONS (ACI 550.5M-18) AND COMMENTARY

CONTENTS

CHAPTER 1 -GENERAL, p. 3 1.1-Inlroduction. p. 3

L. 2-Scopc, p. � I .3-Structural drawings. p. � U-Units. p. 5

CHAPTER 2-NOTATION AND DEFINITIO N S, p. 6 2.1-Notation., p. 6

2.2-Definitions. p. 6

CHAPTER 3-REFERENCED STANDARDS, p. 8

CHAPTER 4-GENERAL CONSID ERATIONS, p. 9 �.!-General design considerations. p. 9 4.2-Materials. p. 9 �.3-Minimum thickness, p. 9 �.4-Tolerances. p. 9

CHAPTER 5-DESIGN FORCES, SEISMIC DEMAND LEVELS, AND ANALYSIS, p. 1 1

5.1-General. p. l l

5 .2-Diaphragm seismic design force. p. 11

5.3-Diapbragm seismic demand level. p. 12

SA-Diaphragm nominal shear strength. p. 13

5.5-Diaphragm modeling and analysis, p. 15

C HAPTER 6-DIAPHRAGM DESIGN OPTIONS, p. 1 7 6. !-General. p. 17

6.2-Eiastic design option. p. 20

6. 3-Basic design option, p. 20

6A-Reduced design option, p. 20

C HAPTER 7-DIAPH RAGM CON NECTIONS A N D REINFO RCEMENT AT JOI NTS, p. 2 1

7.1-General. p. 21

7.2-Connection classifications, p. 21

7.3-Dcfonned bar reinforcement. p. 22 7.4-Special inspection, p. 22

AS-COMMENTA RY REFERENCES AND ACRO NYMS, p. 23

R8.1-References. p. 23

R8.2-Acronyms. p. 23

American Concrete Institute Copyrighted Material-www.concrete.org

DESIGN OF PRECAST CONCRETE DIAPHRAGMS FOR EARTHQUAKE MOTIONS (ACI 550.5M-1 8) AND COMMENTARY 3

CHAPTER 1--GENERAL

1.1--l ntroduction 1 . 1 . 1 Consistent with ACI 3 1 8M requirements for anal

ysis, tlus standard specifics expected perfonnancc and

design requirements for precast concrete diaphragms subject

to earthquake loading. nus standard is meant to replace the

design procedure for precast concrete diaphragms for struc

tures assigned to Seismic Design Category (SDC) C, D, E,

or F that was developed and accepted for use by ASCE/SEI 7- 1 6 in Section 1 4.2.4. The procedure described herein and that of ASCE/SEI 7- 16 supplement the provisions of Chapter 1 8 of ACI 3 18M- 1 4 and do not supplant them

1 . 1.2 The procedure described herein may also be used for

precast concrete diaphragms in structures assigned to SDC B.

R1--GENERAL

R1.1--lntroduction Precast concrete diaphragms are extensively used for

parking stmctures and residential and commercial build

ings. Those diaphragms frequently consist of large precast,

prestressed concrete members such as double-tee (DT)

or hollow-core (HC) members. Double-tee members are

c01mected to one another through discrete mechanical

connections or by reinforcement that crosses the joint between

members. Industry practice is to use these DT diaphragms in

an tmtopped condition in buildings assigned to SDC A and B, and in a topped condition in buildings assigned to SDC

C, D, E, or F. Hollow-core members are primarily used in an untapped condition in buildings assigned to SDC A and B.

Design requirements for precast concrete diaphragms

are covered by the general provisions of ACI 3 18M. However, unless a precast concrete diaphragm includes

a topping tlmt meets all tl1e prescriptive requirements for

diaphragms in Chapter 18 of ACI 3 1 8M- 1 4, the precast concrete diaphragm cannot be designed directly using that

clmpter. For DT diaphragms made composite witl1 a topping

or without a topping, structural integrity and force transfer

witlun tl1e diaphragm are provided by the discrete web and

chord connections that join tlle individual precast concrete

members. If a precast concrete diaphragm made composite

witl1 a topping or without a topping is to provide a struc

tural system with an earthquake loading perfomumce equal to or exceeding that of a comparable cast-in-place concrete

diaphragm, accurate knowledge of the strength, s1iffness,

and defonnability of tl1e individual cOimections used in

the diaphragm is needed. Results from tests on individual

com1ections in accordance with ACr Standard 550.-l-M-18 are needed to obtain the infonnation on stiffness, shear strength,

tensile strengtl1, and tensile deformation capacity required

for tl1e design of c01mections and reinforcement at joints for precast concrete diaphragms satisfying tl1e lateral load

perfonnance reqtrirements of tllis standard, Section 1 2 . 10 .3 of ASCE/SEI 7- 16, and Chapter 18 of ACI 3 18M-1 4.

Post-earthquake reconnaissance following the 1 994 Nortllridge eartl1quake (IYerson and Hawkins 1 994) revealed that when precast concrete diaphragms "vith topping of 75 nun or less were subjected to significant earthquake motions, tlte

topping was likely to crack along the edges of tile precast

concrete members. Consequently , reinforcement crossing

the edges was susceptible to damage and the degree of

susceptibility increased as tl1e aspect ratio for t11e diaphragm

increased and as tl1e larger dimension of the diaphragm

between seistllic-force-resisting vertical elements increased.

Those observations on tl1e behavior of large precast

concrete diaphragms resulted in a comprehensive research

study (Fleischman 20 1 4) to develop better design models for precast concrete diaphragms and comprehensive studies of

the strengtll and defom1ation capacity of diaphragm cotmec

tions. I n the improved design methodology resulting from

that research, the choice of connection type is tied to the

tension defonnations and shear overstrength needed in the

diaphragm to achieve tl1e required design perfonnance.



CODE

1.2-Scope 1 .2 . 1 This standard shall apply to precast concrete

diaphragms and collectors that are part of the seismic-forceresisting system in structures assigned to SDC C, D, E, or F. ll is pennissible to use this standard for the design of the same elements in structures assigned to SDC B.

1 .2.2 This standard shall apply to precast concrete diaphragms, including a) through c):

a) Diaphragms that consist of a cast-in-place composite topping slab with a thickness of less than 75 mm on precast concrete members

b) Diaphragms that comprise precast concrete members with end strips fonned by either a cast-in-place composite topping or edge beams

c) Diaphragms of interconnected precast concrete members without cast-in-place concrete topping.

1.3-Structural d rawings Structural drawings for precast concrete diaphragms shall

show all features of the members into which the connectors or reinforcement at joints are cast t11at are essential to tlle intended seismic performance of the diaphragms and all details of the connections or reinforcement at joints essentiaJ for attaimnent of tltat intended performance.

Essential details shall include: a) The anchorage of the com1ectors and reinforcement at

joints into the precast concrete member b) The procedures and materials by which the connection

between cmmectors in adjacent members shall be made and the tolerances that are acceptable

c) Supplemental reinforcement that shall be included in U1e precast concrete members to ensure that the perfonnance of the member under earthquake loading does not materially affect ilie measured response of the connections between members

d) The metJtods to be used to ensure composite action, as specified in the design, between topping and precast concrete member

e) The connection of the collectors and the adjacent precast concrete members to t11e vertical elements of the seismic-force-resisting system

f) The quality control and special inspection procedures governing placement of connectors and completion of connections

COMMENTARY

Where connections wiU1 lilnited defonnation capacity are used, the earthquake design forces need to be higher than for ductile cotmections. The choice of the appropriate overstrength that should be used in diaphragm design requires detailed knowledge of t11e strength and defonnation capacities of t11e diaphragm connections for the differing combinations of force and deformation ex'Perienced by the connections.

R1.3-Structura l drawings

Reinforcement details in the vicinity of the connectors and the means and procedures by \Vhicb the cormections between t11e precast concrete members are completed affect the perfonnance of the co1mection. Details should be specified completely, including tolerdltces, and fully docmnented on tl1e structural drawings for tl1e diaphragm.



CODE

1.4-Units The official version of this standard is the English language

version using inch-pound units published by the American Concrete Institute.

COMMENTARY



CODE

CHAPTER 2 -NOTATION AND DEFIN ITIONS

2 . 1 -Notation

AR = diaphragm aspect ratio L diaphragm span MCER =risk-targeted maximum considered earthquake N = number of stories Rs = diaphragm design force reduction factor daHD= minimum required deformation of a high deform

ability element 'baMD= minimum required deformation of a moderate

deformability element no calculated shear overstrength factor for basic

design option

QR calculated shear overstrength factor for reduced design option

n,. diaphragm shear overstrength factor

2 .2-Definitions

ACI provides a comprehensive list of definitions through an online resource, "ACI Concrete Tenninology." Definitions provided herein complement that resource.

aspect ratio-diaphragm span-to-depth ratio as defined in 5.3 .5.

connection-region where two a�jacent precast concrete members are joined mechanically, including the bar, weld metal, or mechanical device, which joins the connectors or reinforcement embedded in the precast concrete members.

connector-fabricated part embedded in concrete for anchorage and intended to provide a load path across a joint between precast concrete members.

design earthquake-earthquake ground motion that is two-thirds of t11e corresponding MCER ground motion.

diaJJhragm-roof. floor, or other membrane or bracing system acting to transfer tlle earthquake loading to the vertical elements of the seismic-force-resisting system.

diaphragm design options (EDO, BDO, RDO)-options implemented for precast concrete diaphragm designed in accordance wiU1 Ulis standard.

(a) Elastic design option (EDO) targets elastic diaphragm response in the maximum considered earU1quake

(b) Basic design option (BDO) targets elastic diaphragm response in the design earthquake

(c) Reduced design option (RDO) pennits limited diaphragm yielding in the design earthquake

flexure-controlled dia (Jhragm-diaphragm with a flexural yielding mechanism, which litnits t11e maximum forces tllat develop in the diaphragm, tllat has a design shear strength greater than the shear corresponding to the nominal flexural strengtJ1.

maximum considered earthquake (MCEn)-most severe eartllquake motion considered by theASCE/SEI 7- 16: procedures for detenn.ining MCER ground motion values are provided in Section 11.4.3 of ASCE/SEI 7- 16.

COMMENTARY

R2-CHAPTERS A N D DEFIN ITIONS

R2 .2-Definitions

connection-in precast concrete members, an assembly of com1ectors or reinforcement at joints with linking parts, welds, and anchorage to concrete.

connector-mechanical device, including any attached reinforcement, embedded in the precast concrete member and used to cmmect adjacent members.

ftexu re-cont.-olled diaphragm-diaphragm in which the fle�:urdl yielding mechanism is typically the yielding of U1e chord tension reinforcement



CODE

nonlinear response history analysis (NRHA)-analysis perfonnance in accordance with Section 16.2 of ASCE/SEI 7- 16.

reinfor·cement at joints-reinforcement t11at crosses joints and is designed to resist shear, axial tensile, and compressive forces from bending moments and longitudinal forces, or both.

shear·-contr'Olled diaphragm-diaphragm that does not meet ilie requirements of a fiex1.ue-controlled diaphragm.

span length-diaphragm span as defined in 5.3 . ..!-.

COMMENTARY

shear·-controlled diaphragm-

!) diaphragm that cannot develop a fiexl.ITal mechanism because of aspect ratio, chord member strength, or oilier constraints. Many precast concrete diaphragms with low aspect ratios are shear-controlled diaphragms.

2) diaphragm that is designed to yield in shear rather than in flexure. In some countries, untapped hollow core (HC) slabs with cast-in-place boundary elements are intended to be in this category (Ellioll et al. 1992; Menegotto and Marti 1996).



CODE

CHAPTER 3-REFERENCED STA N DARDS American Concrete Institute (ACJ)

ACI 117M-10(15)-Speci:fications for Tolerances for

Concrete Construction and Materials and Commentary

ACI 3 18M-14-Building Code Requirements for Struc

tural Concrete and Commentary

ACI 550.4M- I 8-Qualification of Precast Concrete

Diaphragm Co1mections and Reinforcement at Joints for

Earthquake Loading A CI ITG-7M -09-S pecificatio n for To Ierances for Precast

Concrete

American .._ocie�v of Civil Engineers (ASCE)

ASCE/SEI 7-16-Minimum Design Loads for Buildings

and Other Structures

ASIA! International

ASTM A615/A615M-16-Standard Specification for

Deformed and Plain Carbon-Steel Bars for Concrete

Reinforcement

ASTM A706/A706M-16-Standard Specification for

Defonned and Plain Low-Alloy Steel Bars for Concrete

Reinforcement

COMMENTARY



CODE

CHAPTER 4-GENERAL CONSIDERATIONS

4.1 -General design considerations 4. 1 . 1 Designs shall consider diaphragm in-plane forces,

diaphragm transfer forces, connection forces, column

bracing forces, and diaphragm out-of-plane forces as described in 12.2.1 of AC£ 3 18M-I-I-.

4. 1 .2 Earthquake loading forces for precast concrete

diaphragms designed in accordance with tllis standard shall

be determined using Section 12.10.3 of ASCE/SEI 7-1 6.

4. 1 .3 1l1e seismic load path for diaphragms shall satisfy

t11e requirements of 18.12.3 of ACI 3 18M-14.

4. 1 .4 Diaphragms shall be designed in two orthogonal directions and consistent with the layout of tl1e ertical

elements of the seismic-force-resisting sy stem to which the

earthquake forces of the diaphragm are transferred.

4. 1 .5 Designs shall provide for tl1e transfer of forces at

diaphragm discontinuities, such as ope1lings and reentrant comers.

4.2-Materials 4.2. 1 Design properties for concrete and steel reinforce

ment shall satisfy 12.2.2 of ACI 3 18M-14.

4.2. 1 . 1 Material strengths specified for connectors shall be

witlrin 10 percent of the specified strengths used for those

com1ectors in the quaJification tests conducted in accordance with ACI 550.4M-l 8.

4.2. 1.2 Concrete strengths specified for the precast concrete elements of tl1e diaphragm shall be witlrin 25

percent of those used for those elements in the qualification tests conducted in accordance with ACI 550.4M-18.

4.2.2 The minimum reinforcement ratio and the spacing

of reinforcement in topping slabs shall satisfy 18.12. 7.1 of ACI 318M-14.

4.2.3 1l1e stress in tendons used as reinforcement to resist

earthquake loading shall satisfy 18.12.7.2 and 18.12.7.3 of

ACI 3 l 8M-14.

4.3-Minimum thickness 4.3. 1 Diaphragms and diaphragm toppings shall have

thickness as required for stability, strengtl1, and stiffness

under factored load combinations and shall satisfy 12.3 and 18.12.6 of ACI 318M-14.

4.4-Tolerances 4.4. 1 Tolerances for posttloning and completion of

connections between tile precast concrete elements of the

diaphragm shall not exceed ±13 mm.

COMMENTARY

R4-GENERAL CONSIDERATIONS

4.4-Tolerances R4.4. 1 The tolerances required by 2 6.6.2 of ACI 318M-14

are considered to be t11e minimwn acceptable standard for reinforcement and com1ectors in precast concrete. Industry



CODE

4.4.2 Where the tolerance of 4. 4.1 is exceeded, the

licensed design professional shall review and approve all modifications in accordance with the procedures specified

in ACI ITG-7M-09.

COMMENTARY

standard product and erection tolerances are provided in ACI

ITG-7M-09. Interfacing tolerances for precast concrete with

cast-in-place concrete are provided in ACI l l?M-10(15).

Tolerances specified in 4.4.1 for completion of connections

are more stringent than tl10se customarily used for precast

concrete diaphragms in structures assigned to seismic

design category (SDC) A and B. However, precast concrete

diaphragms for structures assigned to SDC B, and designed in accordance with this standard, need to satisfy 4. 4. 1.


DESIGN OF PRECAST CONCRETE DIAPHRAGMS FOR EARTHQUAKE MOTIONS (ACI SSO.SM-18) AND COMMENTARY 1 1

CODE

CHAPTER 5 -DESIGN FORCES, SEISMIC DEMAND LEVELS, AND ANALYSIS

5 . 1 -General

Precast concrete diaphragms, their chords, and collectors

shall be designed for strength level seismic forces as speci

fied in 5. 2.

5 .2-Diaphragm seismic design force

5.2. 1 Diaphragm seismic design forces for Seismic Design

Category (SDC) C, D, E or F shall satisfy a) or b):

a) For diaphragms consisting of cast-in-place noncom

posite topping slab on precast concrete members, forces

shall be determined in accordance with Sections 12.10.1 and

12.10.2 or 12.10.3 of ASCE/SEI 7-16, as appropriate.

b) For all precast concrete diaphragms defined in 1. 2. 2,

forces shaH be detennined in accordance with Section 12. 10.3 of ASCE/SEI 7-16

5.2.2 Chords and collectors of the precast concrete

diaphragms defined in 1. 2. 2 shall be designed in accordance

with Section 12.10. 3 of ASCE/SEI 7-16.

5.2.3 Precast concrete diaphragms in SDC B shall be

pem1itted to be designed for the seismic force specified in

Section 12.10.3 of ASCE/SEI 7-16.

5.2.4 Diaphragms designed in accordance with Section

12.10.3 of ASCE/SEI 7-16 shall usc diaphragm force reduc

tion factors Rs as specified in Table 12.10.3.5-1 of ASCE/

SEI 7-16.

5.2.5 Values of R, shall depend on the seismic demand

level as specified in 5.3 and the diaphragm design option

selected in accordance with Chapter 6.

COMMENTARY

R5-DESIGN FORCES, SEISMIC DEMAND LEVELS, AND AN ALYSIS

R5 .2-Diaphragm seism ic design force

The diaphragm seismic design force specified in Section

12. 10.1 ofASCE/SEI 7-16 first appeared in the 1985 Unifonn

Building Code (UBC 1985). The force levels specified by

the 12.10.1 formula were established by empirical consid

erations rather than by rational methods of analysis. Sy stem

performance should theoretically require that diaphragms

have sufficient strength and ductility to mobilize the inelastic

behavior of the vertical elements of the lateral-force-resisting system. The forces specified by Section 12. 10. 1 of ASCE/

SEJ-7-16 do not ensure that behavior (Iverson and Hawkins 199-l ).

Analytical as well as ex'}Jerimental results from shaking

table tests have shown that diaphragm forces over much of

the height of a structure in the design level earthquake may,

at times during the earthquake, be significantly greater Hum the forces specified in Section 12. 10. 1 of ASCE/SEI-7-16

particularly where diaphragm response is near-elastic. M ate

rial-specific factors related to overstrength and deformation

capacity . and geometry-specific factors, probably account

for tl1at behavior. However, for diaphragms tlmt have high

aspect ratios and large spans between the vertical elements

of the seis1nic-force-resisting system, as is the case for many

large precast concrete parking decks, the forces specified in

Section 12. 10. 3 of ASCE/SEI 7-16 better represent a11tici

pated behavior. The forces in Section 12. 10.3 present an

elastic diaphragm force as the statistical sum of tl1e first and

higher mode effects of tl1e structure (Rodrit,'Uez et al. 2002).

In recognition of the defom1ation capacity and overstrengtl1

of tl1e diaphragm. the elastic design force is reduced by a

diaphragm force reduction factor R.,. The development of

the specified Rs values is discussed in Section C12.10.3.5 of

ASCE/SEI 7-16 and Ghosh ct al. (2017). The resultant design

force level is not significantly di.ffcrent from the design force

level of Section 12.10.1 of ASCE/SEI-7-16 for many prac

tical situations. However, for higher diaphragm aspect ratios

and longer diaphragm spans, as is likely in precast concrete

parking decks, the design force levels of Section 12.10.3 of

ASCE/SEI-7-16 ca11 be significantly greater tl1an tl1ose of

Section 12.10.1 of ASCE/SEI-7-16. Therefore, tl1e proce

dures of Section 12.10. 3 of ASCE/SEI 7-16 are required for

the determination of design force levels for precast concrete

diaphragms in buildings assigned to SDC C, D, E, and F (Ghosh 2016).



CODE

5 .3-Diaphragm seismic demand level 5.3. 1 A diaphragm seismic demand level of low. moderate,

or high shall be dctennined for each diaphragm, based on a) through d):

a) SDC assigned to the stmcture b) Number of stories in the structure, N c) Diaphragm span L, as defined in 5.3 .4 d) Diaphragm aspect ratio AR, as defined in 5.3 .5

5.3.2 For structures assigned to SDC B or C, the seismic demand level shall be permitted to be designated as low.

5.3.3 For structures assigned to SDC D, E. or F. the seismic demand level shall be detennined in accordance with Fig. 5 .3 .3 and the fol lowing:

a) If AR is greater than or equal to 2.5 and Ute diaphragm seismic demand level is low according to Fig. 5 .3 .3 , the diaphragm seismic demand level shall be changed to moderate.

b) I fAR is less than 1 . 5 and the diaphragm seismic demand level is high according to Fig. 5 .3 .3, the diaphragm seismic demand level shall be permitted to be changed to moderate.

13' '--'

tl) (I)

. ......

£ CZl '+-< 0 [)

1 z

8 7 6 5 4 3 2 1

0 0

Low

1 0

High

Moderate 1 I I

r23 :r43 20 30 40 50

Diaphragm Span L (m) Fig. 5.3.3-Diaphragm seismic demand level.

r ss 60 70

5.3.4 Diaphragm span of a structure, L, shall be the maximum diaphragm span on any floor in the stmcturc in any direction. The diaphragm span in a particular direction

on a particular floor level shall be t11e larger of the maximum distance between two lateral-force-resisting system (LRFS) vertical elements and twice t11e exierior distance between the outer LFRS vertical element and tlle building free edge.

5.3.5 Diaphragm aspect ratio AR shall be the diaphragm span-to-depth ratio using the diaphragm span L, defined in 5 .3 .4. The diaphragm deptll shall be the diaphragm dimension perpendicular to the diaphragm span between Ute chord lines for the diaphragm or portion of diaphragm.

COMMENTARY

R5 .3-Diaphragm seismic demand level The global ductil ity demanded of a diaphragm in an

MCER level event depends on the seismic demand level defined in 5 . 3 and t11e design option for the diaphragm selected in accordance with Chapter 6. The jointed nature of precast concrete systems results in the load paths 3 but ::; 6

b) Diaphragms in stmctures assigned to SDC D, E, or F wit11 diaphragm spa11 > 23 m but :S 58 m and nwnber of stories ::; 2

c) Diaphragms in structures assigned to SDC D, E, or F wit11 diaphragm span > 23 m but ::; 43 m and number of stories > 2 but :S 4

d) Diaphragms in structures assig11ed to SDC D, E, or F with diaphragtn span :S 23 m

e) Number of stories :S 3, and diaphragm aspect ratio � 2.5 1) Diaphragms in stmctures assigned to SDC D, E, or F,

categorized as high seismic demand level in accordance with Fig. 5 .3 .3, and with diaphragtn aspect ratio < 1 . 5


DESIGN OF PRECAST CONCRETE DIAPHRAGMS FOR EARTHQUAKE MOTIONS (ACI 550.5M-1 8) AND COMMENTARY 1 3

CODE

5 .4-Diaphragm nominal shear strength Diaphragms designed in accordance 5 .2 .4 shall have

nominal shear strengths Qj limes the in-plane shear strength determined using the seismic design force. The

COMMENTARY

Lm (a) Office building

Lm (b) Parking garage with exterior wall

L. Lm Le (c) Parking garage with interior wall

Fig R5. 3-Typical precast concrete diaphragm layouts.

H igh seismic demand level : 1 ) Diaphragms in structures assigned to SDC D, E, or F

with diaphragm span > 58 m

2) Diaphragms in structures assigned to SDC D, E, or F with diapluagm span > 43 m and number of stories > 2

3 ) Diapluagms in structures assigned to SDC D, E, or F with diapluagm span > 23 m a11d nwnber of stories > 4

4) Diaphragms in structures assigned to SDC D, E, or F

with number of stories > 6.

R5 .4-Diaphragm nomi nal shear strength The diapluagm shear overstrength factor Q,, is applied in

the design of diaphragm shear reinforcement and connections crossing joints. The purpose of this factor is to keep the diaphragm shear response elastic while the diapluagm



CODE

diaphragm shear overslrengtb. factor shall equal 1 .4Rs and the strength reduction factor shall equal 0.75.

COMMENTARY

develops inelastic flexural action, as is anticipated for the basic design option (BDO) in the MCER, and for the reduced

design option (RDO) in both the design earthquake and the MCER. No inelastic diaphragm response is anticipated for the elastic design option (EDO).

The value of the diaphragm shear overstrength factor is Q" = 1 .4Rs, a11d values for Rs are specified in 1 2. 10 .3 of ASCE/ SEI 7- 1 6. The vaJues of the diaphragm design force reduction factor Rs are 0.7, 1 .0, and 1 .4 for the EDO, BDO, and RDO, respectively. Tltis translates into diaphragm shear overstrength factors Q" of 1 .0, 1 .4, and 2.0 (rounded to one decimal place) for the EDO, BDO, and RDO, respectively.

The diaphragm shear overstrengU1 factor Q" is applied to the diaphragm design forces and, therefore, requires an

increase in U1e shear strength of U1e diaphragm relative to its flcx'Ural strengUL As implied by tile foregoing Q, values, the level of overstrengtb required relative to the diaphragm flex'Ural strength varies with the design option. The RDO requires a higher overstrengU1 than tl1e BDO due to tl1e larger anticipated inelastic action. For tl1e EDO, no overstrengU1 is required because t l1e diaphragm design force itself targets elastic behavior in the MCER. The nontinal shear strength required for the diaphragm in all three design options is constant, regardless of design option, because t11e parameter Rs in tile overstrength factor is cancel led out by t11e R, in the denontinator of tile diaphragm design force expression given in Section 12 . 10 .3 of ASCE/SEI 7- 16 . The diaphragm design force at level x, FP.., equals Cpxw p./Rs or F nfR., where F r:r is the inertial horizontal force at level x defined as the product of the mass w P.' tributary to the diaphragm at level x and the peak horizontal floor acceleration at tl1at level, p.

DESIGN OF PRECAST CONCRETE DIAPHRAGMS FOR EARTHQUAKE MOTIONS (ACI 550.5M-1 8) AND COMMENTARY 1 5

CODE

5 .5 -Diaphragm modeling and analysis 5.5. 1 Modeling and analysis procedures shall satisfy tile

requirements of Chapter 6 of ACI 3 1 8M- l �.

5.5.2 Any set of reasonable and consistent assump

tions for diaphragm effective stiffness, compatible witl1 the appropriate design option described in Chapter 6, shall be permitted for caJculatjon of diaphrdgm in-plane deflection.

5.5.3 Calculation of diaphragm in-plane design moments, shears, and axial forces shall be consistent witl1 requirements of equilibrium. boundary conditions, and the selected design option.

COMMENTARY

diaphragm at ti1e critical shear joint as tile diaphragm developed a flexural mechanism (in oilier regions of the floor) at the MCER level hazard, and scal ing it by the design shear or required shear strength, II,,. Accordingly :

a) The diaphragm shear factor for the EDO, is unity (Q .. = 1 .0 :::: 1 .4R,, where Rs = 0.7 for EDO) because elastjc diaphragm response is expected in the MCER for EDO.

b) The diaphragm shear amplification factor for the BDO is taken as an upper botmd on the Vm""JV,, ratio for the BDO design under the MCER level hazard.

c) The diaphragm shear an1plification factor for the RDO is taken as an upper bmmd on the Vma)V,, ratio for the RDO design under ti1e MCER level hazard.

Figure R5.4 shows a scatter plot of tile VmmJr;;, ratios from

NRHA for different numbers of stories n and diaphragm AR at the maximum considered earU1quake. Solid symbols

are results where the vertical elements of the lateral-forceresisting system are walls, and open symbols are results where those elements are frames. TI1e data represent the mean of tl1e maximum responses from five ground motions. The expression provided for Q.,, n .. = l .4R,, is plotted as a horizontal broken l i ne on each plot, indicating that the expression provides a constant upper bound for the :mticipated required elastic shear forces for all design cases.

The diaphragm design force reduction factors Rs for precast concrete diaphragms are specifical ly tied to design and detailing requirements, so i liat the ductil ity and overstrength necessary for expected diaphragm perfonnance

are achieved. Chapters 6 and 7 arc based on the diaphragm seismic design methodology (DSDM), the product of a multi-university research project (Fleischman 20 1 4), and give detail ing requirements for diaphragms constructed of precast concrete members in SDC C, D, E, or F, consistent with the Rs factors. These detail ing requirements are in addition to t l10se of ACI 3 1 8M. The derivation of diaphragm design force reduction factors is described in the Conunentaries to Chapters 6 and 7.



CODE COMMENTARY

1 .8 no I BOO I • n=2 1 .7 • n=4 1 .6 n=6

1 .5 1 .4

nv=1 .4Rs� - - - - - - - - - - - - - - - - - - - - -

1 .3 1 .2 1 . 1

l

2.6 2 .4 2 .2

2 1 .8 1 .6 1 .4 1 .2

1

Fig.

"

•

0 1

nR

0 1

D L

!:::. • AR

2 3 4 5 (a)

I ROO I • n=2 • n=4

Qv=1 .4R5 n=6

- - - - - -� - - - - - - - - - - - -

•

AR

2 3 4 5 (b)

R5. 4-Diaphragm shear amplification factor from

l\TRifA at 'v!CER: (a) BDO; and (b) RDO.



CODE

CHAPTER 6-DIAPH RAGM D ESIGN OPTIONS

6.1 -General

A diaphragm design option shall be assigned for a given

structure. The option shall be based on the lowest classifica

tion of the defonnability of the connection or reinforcement

at joints, as defined in Chapter 7.

COMMENTARY

AS-D IAPHRAG M DESIGN OPTIO N S

R6.1-Diaphragm design options

The intent of tl1e design procedure is to provide tl1e

diaphragm with the proper combination of strengtJ1 and

defonnation capacity to survive anticipated seismic events.

Three different design options are provided to the designer

to accomplish tllis objective, ranging from a fully elastic

diaphragm design under tl1e MCER to designs t11at permit

significant inelastic deformations in the diaphragm under

ilie design eart11quake. The motivation for tllis approach

is the recogrlition thaL under certain conditions, a precast

concrete diaphragm desigtled to remain fully elastic up to

the MCER may not be economical or reliable. Under otJ1er

conditions, however, a diaphragm designed to remain elastic

up to the MCER will perfonn satisfactorily and may be the

most desirable.

The methodology allows tl1e three design options related to deformation capacity as follows:

I ) An EDO, where tl1e diaphragm is designed to tl1e Ilighest force levels, calibrated to keep tl1e diaphragr 11 elastic

not only for tl1e desigtl eartllquake, but also in an MCER.

In exchange for the lligher design force, tllis option pemlits ilie desigr1er to detail tl1e diaphragm witl1 low-defonnabilit:y

cmmections or reinforcement at joints (LDE) iliat need not meet any specific defom1ation capacity requirements.

Tbis option is limited in its use. The three diaphragm

seismic demand levels (low, moderate, and bigh) defined in

5 . 3 limit the design option tl1at can be used based on building height, diaphragm geometry, and seismic hazard level. The

use of the EDO is not pennitted where the diaphragm has a

high seismic demand level.

2) A BDO, in wllich tl1e diaphragm is designed to a force level calibrated to keep the diaphragm elastic in tl1e design

eartl1quake, but not necessarily in the MCER. The design

force level is lower tllilll that required for t11e EDO, but

this option requires moderate-defom1ability connections or

reinforcement at joints (MD E), or better, that have inelastic

deformation capacities sufficient for the anticipated defor

mation demands in an MCER.

Tbis option and the reduced design option (RDO) require

the use of a diaphragm shear overstrength factor Qv to

assure that a nonductile shear failure does not occur prior

to the connections or reinforcement at joLnts reaching their

intended inelastic defonnation. TI1e inelastic defonnation is

associated with joint opening due to diaphragm fl ex'Uf e and

not joint sliding deformation due to shear.

3 ) An RDO, in wllich tl1e diaphragm is designed for tl1e lowest desigt1 force level.

Because the design force level is lower in the RDO tl1an

in the BDO, y ielding in tl1e diaphragrn is anticipated in the

design earthquake. The Rs values that detennine tl1e seismic design force levels have been calibrated so U1at diaphragm

inelastic defonnation demands in an MCER are approximately two-thirds of tl1c defonnation capacity of 1 5 mm specified in 7.2.3 for high-defonnability elements (HDE).

American Concrete Institute Copyrighted Material-www.concrete.org cOc1\


CODE COMMENTARY

Each design option can be used with its associated seismic

demand level or a lower seismic demand level. A 1 5 percent diaphragm seismic design force increase is applied when a diaphragm design option is used for a seismic demand level that is one higher than its associated seismic demand level and use of the EDO is not pennitted for a high seismic demand level diaphragm. There may be different types or details of connections used within a precast concrete diaphragm. The diaphragm design option used must be based on the connection \:vith the least defonnability classification.

The BDO has two perfonnance targets: 1 ) elastic diaphragm response in the design earthquake; and 2) diaphragm connection and reinforcement at joint defonnation demands (that is, joint opening) in the MCER within

the allowable defonnation capacity baMD of connection or reinforcement at joints in the MDE category. The diaphragm design force levels for the BDO are al igned with the first perfonnance target . Attainment of the second performance target hinges on the selection of tl1e value for baMD relative to t11e diaphrdgm inelastic deformation demands anticipated for the MCER. These a11ticipated defonnation demands were established through nonlinear response history analysis (NRHA) of precast concrete stmctures with diaphragms designed to the BDO force levels. and subjected to spectmm-compatible ground motions scaled to the MCER.

Practical considerations affected the selection of baMD· The allowable deformation of H DE, baHD, requrred for the RDO was established based on the best-performing precast concrete diaphragm cotmections available at the time this standard was developed (Rcn and Naito 20 1 3 ) . The bestperfonning connections in the database achieved a maximum dependable deformation of 1 5 mm. Therefore, the maximum deformat ion demand, based on subsequent studies (Zhang et al 20 1 1 ; Fleisclm1an 20 1 4 ), was set at lO nun and, tl1erefore, two-tllirds of the 1 5 nu11 value. Because LDEs did not have a deformation requrrement, t11e MDE allowable defomwtion demand value should reside somewhere near half the H DE value, or ?J}"fD = 5 tmn.

The NRHA results for tlte MCER are shown in Fig. R6. 1 . These results show U1at fJ}"fD = 5 nm1 was an appropriate and viable choice for ilie MDEs used in U1e BDO, provided the diaphragms were in the moderate seismic demand level (solid triangular markers in Fig. R6. l ) or in the low seismic

demand level (solid circular markers in Fig. R6. l ). However, tllis value did not produce compliant designs for diaphragms

in the high seismic dema11d level (solid square markers in Fig. R6. l ) and, tlms, some measure was required to bring the design procedure into conformance.

A choice existed in how to modify U1e design procedure to resolve tllis nonconfonnance to tl1e design target:

a) The allowable defonnation ranges for U1e diaphragm c01mections and reinforcement at joints could be modifiedthat is, a more stringent qualification defonnation requirement for MDE-leading to an increase in baMD·

b) The diaphrag1n seismic design forces for all tlrrce design options could be increased and, therefore, tbe design earth-



CODE COMMENTARY

quake perfonnance target for elastic diaphragm response changed from the diaphragm yield point itself to a lower value within the diaphragm elastic range.

c) Create a special requirement for the nonconfonning diaphragm case-that is, increase the diaphragm forces only for nonconfonning cases.

Choice a) did not align well with the typical deformation capacities of the then-existing c01mections, and would not produce evenly-sized deformation ranges for the LDE, MDE, and H DE classifications. Choice b) not only produced overly conservative designs for many cases, but also blurred the clean BDO perfonnance target of elastic diaphragm response in the design earU1quake. For these reasons Choice c) was considered the most desirable.

Thus, raU1er U1an increase the value of '6;�.ro to accommodate the diaphragms in the high seismic demand level, it was decided to keep baMD = 5 mm and create a special requirement for confonnance in the case of diaphragms in the high seismic demand level . Each design option was developed with an associated diaphragm seismic demand level and performance in mind. Where nonconformance did not occur at the associated seismic desigu level-U1at is, the moderate seismic demand level-but instead at the high seismic den1and level, a special requirement was considered of using the seismic diaphragm design force associated with the more demanding seismic demand level.

The special requirement was an increase in lhe design force for the nonconfonning case. The magnitude of Ute design force increase is 1 5 percent. The manner in which this value was established is also shown in Fig. R6. 1 . As mentioned previously, t11e solid square markers indicate the maximwu diaphragm connection and reinforcement at joints defonnation demand (joint opening demand) for tl1e BDO for high diaphragm seismic demand levels and indicate demands greater than 8a"·m = 5 mm. TI1e hollow square markers indicate the maximum diaphragm connection and reinforcement at joints defonnation for these same cases with U1e 1 5 percent increase il1 diaphragm force. This design force increase is seen to bril1g the defom1ation demand within U1e allowable l i mit. The same design force increase is enforced in 6.2 for use of U1e EDO wiU1 the moderate seismic demand level, though tllis provision ·was not based on any quantitative analytical results.

8

I 5 3

() 0

- -!' - - - - - - - · r------, • High .a. Moderate • Low - - - - -:- - - - - -;, - -= :6- --]- - - - - - - ·

- n=4 n=2

3() 60 90 Length (m)

Fig. R6. }-Diaphragm maximum joint opening in NRHAfor

BDO designs under the MCEg



CODE

6.2-Eiastic design option

Any deformability classification of connection or reinforcement at joints is permitted to be used with the elastic design option (EDO) and, therefore, such use is penrutted for:

a) Low seismic demand level b) Moderate seismic demand level, provided the diaphragm

design force is increased 1 5 percent

6.3-Basic design option Either moderate defonnability elements (MDE) or high

defom1ability elements (HDE) shall be used with the basic design option (BDO) and, therefore, such use is permitted for:

a) Low seismic demand level b) Moderate seismic demand level c) High seismic demand level, provided tl1e diaphragm

design force is increased 1 5 percent

6.4-Reduced design option

H igh defom1ability elements (HDE) shall be used with the reduced design option (RDO) and, t herefore, such use is permitted for all seismic demand levels.

COMMENTARY



CODE

CHAPTER 7-D IAPHRAG M CONN ECTIONS A N D REINFORCEMENT AT JOINTS

7. 1 -General

7. 1 . 1 Precast concrete diaphragm com1ections and reinforcement at joints shall be assigned to a defonnability classification based on reverse cyclic tension tests conducted in accordance with ACI 550 -lM- 1 8.

7. 1 .2 Precast concrete diaphragm connections or reinforcement at joints shall be classified as low, moderate, or high defonnability elements in accordance with Table 7. 1 .2.

Table 7. 1.2-Connection deformabil ity classification

Element dt>fonna bil ity Dcfonnability based onACI 550.41\1-18 testing

Low Less than 8 mm

Moderate Between 8 nun and less than 1 5 nm1

High I 5 mm and greater

7.2-Connection classifications 7.2.1 Low-deformability element (LDE)-Com1cctions or

reinforcement at joints used in precast concrete diaphragms

with tension defonnation capacity, as detennined by the testing required by 7 . 1 . 1 , less than 8 tmn.

7.2.2 lvfoderate-deformability element (Jv/D£)-Connec

tions or reinforcement at joints used in precast concrete diaphragms with tension deformation capacity, as determined by the testing required by 7 . 1 . 1 , greater than or equal to 8 mm but less than 1 5 mm.

7.2.3 High-deformability element (HDE)-Connections or rei nforcement at joints used in precast concrete diaphragms with tension deformation capacity, as dctcnnincd by the testing required by 7 . 1 . 1 , greater than or equal to 15 mm.

COMMENTARY

R7-D IAPH RAGM CONNECTIONS A N D REINFO RCEMENT AT JOINTS

R7.1 -General The precast concrete diaphragm seismic design metllOd

ology (DSDM) uses an approach that requires knowledge of t 11e diaphragm cotmection or reinforcement stiffness, deformation capacity, and strength to effectively and efficiently design the diaphragm system for seismic forces. To meet this need, it is critical tl1at the connection or reinforcement properties be detennined in a repeatable, reproducible, and consistent manner so that existing and new connections can be used effectively in the diaphragm system. The qualification protocol in ACI 550-lM- 1 8 provides an ex.'))erimental approach for the detennination of connection or reinforce

ment properties. The testing establ ishes the strength, stiffness, and defonnation capacity of tJ1e connections and reinforcement at joints under i11-plane shear and in-plane tension.

As a minimwn, in-plane monotonic and cyclic tension tests are conducted. If shear performance chardcteristics are desired, monotonic and reverse cyclic shear tests need to also be performed for detennination of the effective y ield displacement in sheai. However. shear perfonnance c l13racteristics do not affect the com1ection classifications of 7 .2.

Precast concrete diaphragms defonn mostly by the strains that occur at the joints between the precast concrete members. The requirements for reinforcement or cotmection defonnabilit:y come from Ute need for the connections to acconunodate tltese strains at tl1e joints. A connection is an assembly of connectors including the linking parts, welds, and anchorage to concrete. Mechanical cmmectors are identified as tl1e primary parts tl1at make tl1e connection, but tl1e deformation capacity identified witl1 t11e connection represents the perfonnance of tl1e entire l i nk across t11e joint. Qualification of the deformation capacity of t11e connection, t11en, is dependent on the details of the entire load path across the joint. The use in design of a connector qualified by testing is only valid when tlle design i ncorporates the complete connection detail ing, as tested.

R7.2-Connection classifications The diaphragm reinforcement classifications are high

defonnability elements (HDE), moderate-defonnability

elements (MDE), and low-defonnability elements (LDE). The tlmshold values of tension deformation capacity for each connection or reinforcement class were selected by considering t11e range of t11e ultimate (cyclic tension

opening) defonmtions exhibited by t11e various precast concrete diaphragm cotmections examined in t11e diaphragm seismic design metl10dology (DSDM) ex.'))erimental program (Ren and Naito 20 1 3). Based on tl1ese results, a threshold deformation of 1 5 mm was selected for HDE cmmections or reinforcement at joints and 8 111111 for MDE connections or reinforcement at joints. There is no defonnation requirement for LDE connections or reinforcement at joints.



CODE

7.3-Deformed bar reinforcement Defonned bar reinforcement (ASTM A6 1 5/A6 1 5M

or ASTM A 706/ A 706M) positioned as chord reinforcement within cast-in-place concrete topping or cast-in-place concrete pour strips and satisfying the cover, lap, and development requirements of ACI 3 1 8M- l -l shall be deemed to qualify as high-deformability elements (HDEs). Reduction of development length for excess reinforcement in accordance with 25.4. 10 of ACI 3 1 8M- 1 4 is not permitted.

7.4-Special inspection For precast concrete diaphragm connections or reinforce

ment at joints classified as high-defonnability elements (HDE), installation of the embedded parts and completion of the continuity of reinforcement across joints, and comple

tion of connections in the field, shall be subject to continuous special inspection as defined in the general building code.

Special inspection shall apply for all connections that use HDE elements, which are rel ied upon for diaphragm seismic performance in structures assigned to Seismic Design Categories (SDC) C, D, E, and F.

COMMENTARY

A factor of safety of 1 .5 was introduced into the design procedure by establishing for each of the three design options of Chapter 6 maximum joint opening demands at two-tltirds

of the cmmection's limiting defonnation capacity as determined by testing in accordance with ACI 550.4M- 1 8. The

two-thirds factor leads to maximum allowable defonnations of 10 mm and 5 mm for the HDE and the MDE, respec

t ively. No defonnation capacity requirement is needed for the LDE because this c lassification of connection or reinforcement at joints is used with designs that result in fully elastic diaphragm response up to the MCER. The allowable joint openings were used as targets in the analytical parametric studies to calibrate the design factors.

The diapluagm cmmection or reinforcement at joints classification is based on inelastic defonnation associated with joint opening due to diaphragm fle>.c'Ure and not joint sliding defonnaUon due to shear. Other reinforcement associated with col lectors and anchordges, secondary connections to spandrels, and similar connections, may have different requirements imposed on them by the defonnations of the diapluagm. Those differences should be considered in determining the required defonnabi lity for those com1ections.

In meeting the required defonnation capacity using the testing protocols in the qualification procedure given in ACI 550.4M- 1 8, the required cumulative inelastic deformation capacity is also met.

R7.4-Special inspection The purpose of this requirement is to verify that the

detailing required for high-defonnability elements (HDEs) is properly executed tluough inspection by personnel who are qualified to inspect these elements. Qualifications of inspectors should be acceptable to the licensed design professional

and to t11e jurisdiction enforcing tl1e general building code.



CODE COMMENTARY

As-COMMENTARY R EF ERENCES AND ACRONYMS

R8.1 -References Au thored documents

Elliott, K. S.; Davies, G. ; and Omar, W., 1 992, '·Experimental and Theoretical I nvestigation of Precast Concrete Hollow-Cored Slabs Used as Horizontal Floor Diaphragms " The Structural Engineer, V 70, No. 1 0, May, pp. 1 75- 1 87 .

Fleischman, R B., 20 1 4, Seismic Design Methodology Document for Precast Concrete Diaphragms, Project 08-07

Deliverable, Charles Pankow Foundation, Vancouver, WA, Feb., 545 pp.

Ghosh, S. K. , 20 1 6, "Alternative Diaphragm Seismic Design Force Level of ASCE 7- 16," Structure Magazine, Mar., pp. 1 8-22.

Ghosh, S. K.; Cleland, N. M: and Naito, C. J . , 20 1 7, "Seismic Design of Precast Concrete Diaphragms," NEHRP Seismic Design Technical Brief No. 1 3, NJST GCR 1 7-9 1 7-47, Natjona1 Institute of Standards and Teclmology.

Iverson, J. K., and Hawkins, N. M., 1 994, "Performance of Precast Prestressed Concrete Building Structures During Northridge Earthquake," PC! Journal, V 39, No. 2, Mar.Apr., pp. 38-55. doi : 1 0. 1 555-t/pcij .030 1 1994.38.55

Menegotto, M., and Marti, G., 1 996 'Diaphragm Action of Precast Floors: Behavior and Modeling," Eleventh World Conforence on Earthquake Engineering, Paper No. 768,

E lsevier Science Ltd. Ren, R., and Naito, C. J., 20 1 3, ' Precast Concrete

Diaphragm Connector Perfonnance Database," Journal of Structural Engineering, V 1 39, No. I , Jan., pp. 1 5-27. doi: l 0. l 06 I/(ASCE)ST. l 943-54 1 X.0000598

Rodriguez, M. ; Restrepo, J. I . ; and Carr, A. J., 2002, "Earthquake I nduced Floor Horizontal Accelerations in Buildings," Earthquake Engineering & Structural Dynamics, V 3 t No. 3, pp. 693-7 1 8. doi : 1 0. 1 002/eqe. 1 49

Schoettler, M. J . ; Belleri, A. ; Zhang D. ; Restrepo, J . ; and Fleisclunan, R. B . , 2009, "Preliminary Results of the Shake-Table Testing for Development of a Diaphragm Seismic Design Methodology," PC! Journal, V 54, No. 1 , pp. 1 00- 1 24. doi: 1 0. 1 5554/pcij .O lO 1 2009. 1 00. 1 24

UBC, 1 985, Unifonn Building Code, I nternational Conference of Building Officials, Whittier, CA, 1 985 .

Zhang, D. ; Fleisclunan, R. B . ; Naito, C. J . ; and Ren,

R., 20 1 1 , 'Ex'})erimental Evaluation of Pretopped Precast Diaphragm Critical Flexure Joint under Seismic Demands " Journal of the Structural Division, V 1 37, No. 1 0, Oct., pp. 1 063- 1074. doi : 1 0. 1 06 l /(ASCE)ST. l 943-54 1X.0000352

R8.2-Acronyms AR: aspect ratio BDO: basic design option DSDM: diaphragm seismic design methodology

DT: double-tee EDO: elastic design option HC: hollow core



CODE COMMENTARY

HDE: high-defonnabi lity element LDE: low-deformability element MDE: modcrate-dcfonnabili.ty clement NRHA: nonl inear response history analysis ROO: reduced design option SDC: Seismic Design Category



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an aci standard · 2020. 5. 12. · for precast concrete diaphragms satisfying tl1e lateral load...

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