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Designing with Paper TirbesCristobal Correa, Assoc. Principal, Buro Happold Consulting Engineers, New York, NX USA

SummaryThis paper details the author's experiences working with paper as a temporarybuilding material in the work of Japanese architect Shigeru Ban. The paper ispresent in these projects as a structural element in the form of a paper tube. Themechanical properties of the material are examined and three projects are pre-sented: Two, which have been designed, built, and dismantled and one which iscurrently being designed for construction in 2005. These projects illustrate thedesign challenges in using this innovative material.IntroductionPaper has emerged as an alternativematerial for use in temporary struc-tures. Its obvious recyclability and lowcost makes it an attractive choice, butits singular nature requires the resolu-tion of numerous design obstacles.Paper is not normally considered aconstruction material, and there areno existing guidelines for its use as astructural element. In order to designwith confidence using this material, itis necessary, first, to understand its spe-cific characteristics. strengths and dis-advantages.Paper Configuration andTestingThe same way that clay is molded intobricks, the paper used in these projectshas been configured into paper tubesfor use as a structural material (Fig. 1).Paper tubes have been manufacturedfor many years for use in the trans-portation and handling of fabrics. Theyhave also been used as shuttering whencasting concrete columns. The fabrica-tion process allows both the diameterand thickness of the tube to be modi-fied to suit the desired application. Thetube can also be rolled to an infinitelength, the only limitation being thetransportation of the finished product.The paper in the tubes can be madefrom fresh or recycled paper pulp thatis pressed into sheets, dried and thenrolled with an adhesive to form thetubes. Natural moisture in the tubesis about 9% with a density of about7000 N/m'.There are no existing specifications forthe manufacture of paper tubes forStructural Engineering International 412004

Fig. 1: Cross section of paper tube used inthe MoMA arch structure.structural uses. For this reason, theprojects detailed below were designedusing data that was obtained from me-chanical testing (Fig.2) of paper tubesamples in recognized testing labora-tories. These tests allowed for the de-termination of mechanical propertiesand the establishment of stress designguidelines for different structural con-ditions.Tests have been done both in Japan

and Germany. The information shownhere is based on the testing done atDortmund University in Germany [4].Some conclusions that can be drawnabout the material from the testing are:- has a stiffness about 1'15 of. a soft-wood- is sensitive to load duration- is sensitive to variations in moisturecontent up to about 7"/". After thisvalue, strength reduces about 10%for every 17o increase- has a significant rate of creep, withcreep occurring with as little as 10%of the failure load- allowable bending stress is generally50%" greater than allowable com-pression stresses.Some of the key design values are pre-sented for illustration purposes (Table 1).Readers should refer to the cited test-ing data for more precise informationon specimen size, testing techniquesand results. Allowable stresses wereobtained by reducing ultimate load bythe appropriate factors. Short term al-lowable stresses are assumed to betwice the value of long term allow-ables.

The paper tubes are very sensitive towater infiltration. Waterproof layerscan be rolled into the tubes in or$er toprovide protection from water infiltra-tion, but at the tube ends the manufac-turing technique leaves paper fibersexposed. These fibers will readily wickup moisture and allow it to enter thetube if they are not treated with asealant. The paper tubes lose strengthif they are wet.

Parameter ShortTerm LongTermYoung's Modulus(N/mm') 1000-1500 1000AllowableCompression Stress(N/mm')

4,4 ))Allowable BendingStress (N/mm') 6,6

aa

Table 1: Paper tube design values

Fig. 2: Testing of paper tubes in GermanyTemoorarvStructures 271

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10 15 20 25 30 3612,500 . 12,500 , 12,500 12,500 . t2,500 12,500 .mmmmmm

Fig. 3: PIan and section view, Japanese Pavilion - Hanover World's FairWith regard to fire resistance, there isno formal rating for the paper tubes,the behavior is similar to that of heavytimber framing. The paper tubes willburn, but they will not support theirown combustion. It is also possible toapply intumescent coatings to the pa-per tube surface to further increase fireresistance. Generally, for the projectsreviewed, there was no significant fireload, so the issue of combustibility wasnot a controlling point in the design.ProjectsJapanese Pavilion, GermanyThe Japanese Pavilion was built for theF{anover World's Fair in 2000 and re-mained in place for seven months. Thebuilding covers approximately 2500 m'(Fig.3).It was conceived as a flexible grid shellstructure that would be assembled andlaid flat on the ground, and then liftedand formed into place by a protrudingscaffolding system that would give it afinal geometry which would be fixatedby a stiff border element at its perime-ter edge. The material for the grid shellis 120 mm diameter,22 mm thick papertubes that are lashed together wherethey cross by plastic straps. The overalldimension of the hall is 15 m by 35 mwith a rise of up to 15,5 m.The design and modeling of this struc-ture was part of an intense design ef-fort which included a form-finding ex-ercise and the construction of physicalmodels (Fig. q in order to determinethe project geometry as well as the pos-sible buckling failure modes. Rigidity isaided by wood arches at regular inter-vals. Steel strut at the ends were incor-porated into the grid at the insistenceof the German checking authoritiesalthough analysis indicated that thesewere not needed (fig. 5).278 Temporary Structures

Axis of Symmetry ofGridshell-\O- " q,s: ti]".t"'l" 1ld o alo .loo. _l@lN-i ..1:o.l

I""1:

r, --, rrr,.....- i:,:,',io .4,800m_ 16.150m 12.650m 4.800millllliiiilill24oomiiiililliliiil : : ,"''=.,,=-"-.-..-'-jlilllllliliiil'liilliitrlitiltt : /'"0'::":"'uc'1ibniilii l il i ilili t t i,/ 3,iiiit""-;ooedRu*p'f''{ ' ' FFB-6e'o5om ''.'l . ..9.j.J-9.J 9-9. ".e .r "'\"' '-a\ Mass at Support , Existing Grade

Compacted Cravel Layer Levelfor Load Distribution

Detailing of the structure involved theresolution of some key connections.These are the cross points betweentwo tubes, the connection of the tubesto the ground plane and the connec-tion of the tubes to the cladding as wellas to the wood ladders. Example detailconstruction for paper tubes will be re-viewed in the next project. The com-pleted structure is shown tn Fig.6.

MoMA Arch, USAThis temporary structure was erectedas part of a retrospective of art and ar-chitecture of the 20th Century at theMuseum of Modern Art in New YorkCity. It is made up of 200 mm diameter,25 mm wall thickness, tube sectionsthat define the top and bottom chordof 600 mm deep paper tube arches.These arches span approximately 24 mand are linked transversally by a paper

Structural Engineering International 412004

Fig. 4: Physical model of Japanese Pavilion

Fig. 5: Japanese Pavilion under construction

Fig. 6: Japanese Pavilion completed

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Splc, iceline"

Tiuss'Grid tube.lo-w--.Grid tube high.

B ,;'.."..N?'...

'7 t\A+r ' Grid tube infill area

Construction unit2 trusses

Fig. 7: Plan and elevation of paper tube arch at MoMA,-,-,---,- ------ -\-^-*

tube grid-shell of 150 mm diameter tubeswith a 25 mm wall thickness (Flg. 7).Cable stiffening ties are also locatedunder the arch and attached to thebottom chord. The overall size of thestructure is approximately 24 mby 24 m.It was installed over the summer sea-son for a period of 90 days.Structural analysis of this structure wasmore straightforward than in Hanover.Grid shell behavior was conservativelyignored in the arch span direction withthe grid shell contribution reduced toproviding lateral support for the span-ning arches.Detailing of this structure was com-plex because of the mixture of materialthat created different connection con-ditions. The top and bottom chords ofthe trusses are paper tubes but the ver-tical and diagonal elements are steelrods and cables. The attachment of thetrusses to the building and base are bymeans of the steel connection plates.Because of the method of construc-tion, element splices were also neces-sary for this project. These details areshown in Flgs. 8,9 and 10.Initial construction took place offsitewhere the roof was laid over a series ofscaffolding elements much the way aship's hull is built in a shape-formingcradle. The grid shell paper tubes weremodeled three-dimensionally in orderto determine the precise location andangles of the pre-drilled holes forthe connections which would followthe project geometry. After the tubesarrived on site, holes were drilled intothem, then the bottom chord was laiddown on the scaffolding, the verticalStructural Engineering International 412004

Facade line above BAOl2mmlomm^Steel pla0onst

Fig, B: Connection detail at baseA19mm

6 mm thickFig. 9: Typical arch construction detail

,Pl-a-stic straps

2100 mm 6lli-'cjFig. 10: Grid shell connection detail

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Fig. 11: Structure complete on scaffoldready to be cut for shipping

Fig. l5: Nomadic exhibition - general configuration elevationelements were inserted, and the gridshell elements were added. The diago-nal truss cables were inserted into thetruss and then the top chord was at-tached (Fig. 11) in order to completethe truss. Once assembled and paintedwith a waterproof coating, the struc-ture was cut into eight half-arch slicesin order to be able to transport it onflatbed trucks to the museum (Fig. 12).Adjacent to the museum site thepieces were partially connected to-gether, lifted into place and then at-tached to the receiving support points(Fig. 13). The completed project isshown in Fig. 14.ltromudic Exhibition, (JSAThis 4000 m2 temporary exhibition hallis intended for a traveling venue thatwill highlight the work of a contempo-rary artist. The hall is approximately20 m wide by 200 m long. It is con-structed of materials typical used intemporary structures including fabric,scaffolding, cribbing and even the con-tainers used to ship them. It has a cen-tral roof support that is made up oftwo large diameter paper tubes sur-mounted by a paper tube triangle thatconnects to the roof ridge (Figs 15 and16).The structural loads on the paper tubescan be determined from a straightfor-ward analysis. The difference from theprevious projects is that in this case al-though the structure is temporary it ismeant to be assembled and disassem-bled a multitude of times. with the

f ,Q - -2,3 ql

Fig. 16: Paper tube connection details tometal plates

added condition that all pieces must beable to fit within a standard 6,1, m con-tainer. For this reason, the paper tubedetailing has been designed in such away as to minimrze the wear and tearon the paper tubes. This has been ac-complished by permanently affixingsteel plates and elements to the papertubes. In this way the connection pointscan be restricted to more durable con-nections which are steel on steel.The project is currently being designedand built and should be installed inNewYork City in March of 2005.It willthen be disassembled and shipped inits own containers to Los Angeles,Tokyo and points beyond.

Structural Engineering International 412004

a Top of triangle''J i)

dc\lr);

A Top of columns'

,?3 --* 5,Q rl

..-.....

Fv)X

Fig. 12: Cut structure on flatbed trucks

210 mm Cable

COL. see elev. 12x75mm50 mm vertical

Fig. 13: Hoisting into museum garden

Fig. 14: Complete installation280 Temporary Structures

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ConclusionPaper has been used successfully in anumber of temporary structures. Al-though there are specific design con-straints to using this material, with care-ful detailing and calculations backed-upby testing results, it is possible to de-sign structures that serve their purposeand are both beautiful and elegant.Most importantly, this work shows thatas engineers we should enthusiasticallyaccept challenges to use materials andtechnologies in new and interestingways. We should not underestimateour strengths as professionals, as manyproblems can be successfully solvedusing first principles, a testing regimeand our own natural inventiveness asdesigners.

References[1]MCQUAID, MATILDA, Shigeru Ban,Phaidon Press,2003.[2] CRIPPS, ANDREW. Constructing a Card-board Building-Design Guide - Internal BuroHappold document unpublished September 2001available at www.cardboardschool.co.uk

[3] CORREA, CRISTOBAL. Nomadic Exhibi-tion - Fire Study Strategy and Literature Review -Internal Buro Happold document October 2003.[4] BLOCK, KLAUS. Report Nr 99.03.01-1 TheStructural Behavior of the Load Carrying PaperMade for the Japanese Pavilion at the EXPO2000, Institut fiir Bauforschung, UniversitiitDortmund. November 1999.[5] CRIPPS, ANDREW. Cardboard as a Con-struction Material: a case study - Building Re-search and Information (May-Ju ne 2004), 32(3),pp. 207 219. www.tandf.co.uk/journals.[6] DICKSON, M.; HARDIE, G.; LEIBLE,INK.; ROGERS, P. AND WESBURY P. The JapanPavilion for the Hanover Expo 2000, paper pre-sented at the IASS-2001 Conference: Theory,Design and Realization of shell and SpatialStructures, 9-13 October 2001, Nagoya, Japan.

SEI Data BlockJapanese Pavilion, GermanyOwner:JETRO - Japan External TiadeOrgantzation, JapanStructural Design:Buro Happold, New York, USAContractors:Takenaka Europe GmbH, GermanYConstruction Date:MoMA Arch, USAOwner:

May 2000

Museum of Modern Art. New York,USAStructural Design:Buro Happold, New York/TakenakaCorporation, USAContractors:Atlantic Heydt Corporation, USAConstruction Date: APril2000Nomadic Exhibition, USAOwner: Bianimale Foundation, USAStructural Design:Buro Happold, New York, USAC o ntr acto r s.' B ovis, USAConstruction Date: FebruarY 2005

Test vour structure with ATE,NAFinite element computer simulationof damage and failurein concrete structuresNow available on-linewww.cervenka.czlvtls

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CERVENKA CONSULTINGPredvoje 22, 162 00 Praha f , CzechRgpqbllc _phone: -*4 202 2061 00 1 8, fax: +4202 2061 2227www. c erv enka.cz, c ervenka @cew enka.cz Softwaredevelopment and distributionconsulting servicesStructural Engineeringlnternational 412004 Temoorarr Structures lE1