.
,. ..:#: , ..;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 SoclellcrInternntlonul Asrocintion for Bridge a n d 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) I n e r n a l i o n a 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 D c s i g n e n ( I R )
The following identifier those firms m d o r g m i w t i o n r w h o 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." A m m a n D L F Univcrsnl Limited. N c w Dclhi Zuhair Fnyez & Arrociales. Jeddvh Juros. B n i m & Bolles. N e w York
Kuwait Foundmion for t h e Advonccmcnt of Sciences. Kuwait Shimizu C o r p o n d o n . T o k y o
T h e T u r n e r Corpomtion. N e w Y a r k Sponsors
Europrofilc Tecom. Luxembourg Gcorge A. Fuller Co.. N e w York
T.R. H n m r a h & Yeung Sdn. Bhd.. Sclangor HL-Technik A.G.. Munich
Hong Kong Lnnd Group Lld.. H o n g Kong Kone Elevators. Helsinki
John A. M n n i n & Aaroc.. Inc.. L o r Angelcr A h m a d Mohnrrom. Cairo
Walter P. Moore & Associates. Inc.. Hourton Nippon Slcel. T o k y o
Otis E l e w l o r Co.. Forminglan O v e A m p P m n e r r h i p . London P D M Strocnl Inc.. Slockton
Leslie E. R o b c m o n Associatea. N e w Y o r k Snmrung Engineering Br Conrtruction Co. Lrd..Seoul Snud Consult, Riyadh
Schindlcr Elevntor Corp.. Morrislown Siecor Corporntion. Hickory Tukenako Corporation, T o k y o
Tishmon Conslruction Corporarion of N c w York, N e w York T i i h m a n Speyer Properties. N c w York
W c i r k o p i & Pickwonh. N e w York
W i n g T a i Conrtmction &Engineering. H o n g Kong W o n g & Ouynng (HK) Lld.. Hong Kong
D o n o r 5
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. T o k y o Steen C o n ~ u l t u n t r Pty. Ltd., Singspore T h c Herrick Corp.. Pleasnnton S y i k o & Hcnnery. lnc.. N e w Y o r k Hollundsche Belon Mnnlschappij BV, nornton-TomorcuilEngineer5. N c w York
Rijswijk Werner Vosr & Ponncrr. Braunrchwcig
Hong Kong Housing Autl~orily. Hong K o n g W o n g Hobach Luu Consulting Engineers. L a 5 lffland Kivvnvgh Waterbury. P.C.. New Y o r k Angcles
C a n l r i b u l o n
Office o f Irwin G. C w l o r . P.C., N e w York L i m ConsulU~tts. Inc.. Cambridge H.K. C h e n g & P n r t n e n Ltd. Hung Kong Meinhnrdt Auslrnlin Pty. Ltd.. Melbourne Douglas Specinlist C o n u n c t o n Ltd.. Aldridgc Mclnhnrdl (HK) Ltd.. H o n g K o n g H n n Conrulwnt Grnup. Snntn M o n i c a M u c r e r Rutledge Consulting Engincen. The G c o r g ~ Hymnn C o n s W c l i o n Co.. N e w Y o r k
Balhrsdn Oboynshi Corpomtion. T o k y o
Ingenicurburo Mullcr Mnrl GmbH. Mnrl O T E P In~crnntional. SA. Mndrid Institute S u l w n lrknndnr. J o h o r 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.. S n o Tecnlcos. Rin d c J n n c i m
Pnulo P S M Inlernnllonnl. C h i c a g o
Johnson Fain a n d P e r r i m Asroc.. L o s Angeler Skilling W a r d 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 Y o u r r e f a n d Arrocinlcr. L o s Angelcs
C o n t r i b u t i n g P n r t l c l p o n l 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 ~ ~~ n y c r Wind Tunnci Labornlory (U. Wcrr- u ~ d ~
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 L b o n l o r ) . 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 l o h n s ~ n o n 1 A s ~ o c i l r r . Cnlcagn Cunrndgc l i n l t n s 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 D l r t r l & lruin 1°C. Gurlph S c p l l o t S a i o rcmnding (Sdnl Bhd, K ~ o l o Lumpur scrrrn S m : m r Gimi5 dc E n c r n h o n ~ S A . Rlo dc
lnncim
Scvcmd Asrociacr Conr. Engn.. New York SOBRENCO. S.A.. Rio d r 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
Council on Tall Buildings and Urban HabitatCommittee 3 CONTRIBUTORS I . D . Berzrretf~ Joseph Bicnls Brian Coviil P.H. D a y o ~ ~ ~ n r ~ s a 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, ChairmanR o b e r t
Sinn,
Vice-chairmanM a x
B.
Kilmister, EditorMcGtaw-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 o f the Tali Building, and Urban Environment Series. Thc edtlonll gmup $ b a s 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: T h e 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 o n e of a series o f Monographs prepared under the aegis o f the Council on Tall 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 b e based on the original effort but would focus more strongly o n the individual topical committees rather than the groups. This would d o two things. It would free the Council committees from restraints as t o 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 i x o t h e r s , 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. Its earlier treatment was n part of Volume SC. I t dealt with the many issues relating t o tall building structural systems when it was published in 1980. T h e com- mittee 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 com- mittee'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. engineer- ing, and construcdon issues that must b e 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; how- ever, it was nnly after World War I1 that rapid urbani'ration and population growth cre- ated the need for the conswction of tall buildings.
T h e
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 exte- rior 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 an- cient 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 struc- tural 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 u h o l e 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 b e 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. I n t r o d u c t i o n 1.1. Condensed Rererenccs/Bibliography2. Classification of Tall Building S t r u c t u r a l S y s t e m s
2.1. Condenrcd RererenceJBibliogmphy
3.
Tall Building Floor S y s t e m s3.1. 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 L o a d R e s i s t i n g 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
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 F m l 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 F i s 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 S w c t u n l 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
Introduction
Smctural s y s t e m 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 pub- lication 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 R g . 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 architec- tural aesthetic. Innovntive s w c t u r a l 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 struc- tural 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, regard- ing 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 should2 Introduction [Chap. 1 I Chap. 11 3
I
b e of interest and value to practicing engineers and architects as well as other tallbuilding enthusiasts.
This Monograph is organized into six chapters. A general introduction to the clas- sification 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 evalu- ated. 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 " &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.
kand 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 proj- ect: "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 effi- cient 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 sys- tems were placed with the idea that the application of any panicular form is economi- cal 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 WallsFrames Trusses Diaphragms
.
Type and magnitude of lateral loads WindSeismic
Strcngth and serviceability rcquirements Drift
Acceleration Ductility
In 1984 the Council attempted to develop a rigorous methodology for the cata- loging 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 11I I
TYPE Ill1
)
TYPE IVI
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 pre- mium 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 subsystemsI
(XX)/
Building configuration and load transfer (XX YY 2) Elevation8 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. ~ o m o o s 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 e x ~ c m e l y 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 compos- ite 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 c o m ~ o s i t e 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 insu- lation on the steel beam. Todny the m o s ~ c o ~ m o n nrrangemmt found in composite
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 com- nosite 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. 3 2 Three First Nntionol Plnm, Chicago, Illiooir, lyplcnl noor.
WORKING ULTIMATE
LOADS LOAD
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 c s u i ~ m e n t 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 mem- bers 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 con- sequent construction cost premiums.
HYBRID
C0MPOSITEBEb.M COMPOSm BEAM BUILT-UP
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 ~ n s i d e r i ~ t i o ~ 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 C o m p o s i t e J o i s t s and T r u s s e s
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.....
....?...
.
.-...
...
.*., TAPERED6
C",I~~~~TE
-..,.
? .. .....
...
DAPPED....
a??+-
V--=d'.
" >.. . .
<: ;-,1
CASTELLATEDLf4-Z
... . . . .. . . .
. . .
. . . ... .,,.,, ., ." ,I I I
<. '-.* t. SYSTEM14 Tall Building Floor Systems [Chap. 3
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 - ~ v e b 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 l e a ~ h ~ l i t y 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. T h e increased depth of the comuosite truss svslcm over a standard rolled-shaoe comnosite beamsystem
with building-scrvices dictwork and piping passing bclbw the'beam results in maximum material eificicncy and high flexural stilfness. Generally, com- posite 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 t h e 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 lengthof 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 spac- ing of the web members should bc chosen such that the free passage of ductwork and piping i s not inhibited while maintaining a reasonable c o m o ~ c s s i o n top-chord
. - .
unbraced lensth. On the other hand. the nnlle =~~ of ~~ the web diaeonalr should L~~~ ~ be made
~ ~
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 com- oosite 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 build- ing in the world when completed.
EXTEA1OR STEEL C O U P O S ~
GR4VITI COLUMNS AIIb SPANDRELS
TYPICALCOMPOSrrE FLOOR TRUSS
16 Tall Building Floor Systems [Chap. 3
7 General Considerations
High-rise oftice buildings usually have long-span floors to achieve the desirable col- umn-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-
m u m m
WARREN TRUSS
Fig. 3.7 Camporilc noor trusr geometries.
CHOilOB h u b l ~ l n g l e m R e e ? . T U k 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 b y walls, which effectively hide the columns. Hence continuous spans can b e achieved. Unlike office buildings, residential buildings do not as a rule have sus- pended ceilings-the ceiling may be just a sprayed h~gh-build coating on the slab sof- fit or a plasterboard ceilina on battens fixed to tbe slab soffit. Flat-plate floors are1
therefore required and deflection control is an imponant design consideration. WhereI 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 M o n o m p h (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 connec- tions 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 speci- fied 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 postten- sioned 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 prestressPPR =
.--!&-
+ 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 1 5 % 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 Systemsl9
I
; ,: :
,
i
Untensioncd steel is then added to satisfy the ultimate limit state. (This will often resultin 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 r a m ~ 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 pock- ets 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
S R E S S I N G
~ i g . 3.11 Construction requcnce I
GROUTING
20 Tall Building Floor Systems [Chap. 3
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 i n thc floor may necessitate some additional t~nte~~sioned reinforcement.
2
Economics of PosttensioningPosttensioned 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 21The 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 a m o ~ n t s of itrand. Tlte influence of strmd "retli~tg losses" is also greater with
ruv
shun strands, thus incrc3sing the area of ten- don required. Nevertheless, even though most tendons in a high-rise building floor will be only around 10 to 15 m (33 to 5 0 it), the system is economical because of sav- ings 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 b e 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.
2 2 Tall Building Floor Systems [Chap. 3
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 geome- try 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 23Tall Building Floor Systems [Chap. 3 S e c t 3.21
3 Cutting
Prestressed
TendonsI
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
26 Tall Building Floor Systems [Chap. 3
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 s m c t u r e 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 corro- sion.
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 installedat 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 demo- lition. 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 storiesNumber of levels below ground Bullding use
Frame m a a n a l Typical floor live load Basic wind velocity Maximum lateral deflcction Design fundamental p e r ~ o d 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 S m a r t &
McCutcheon Connell Wagner 1991 21 1 m (692 ft) 5 4 3 Office
Concrete core, steel floor beams
3-kPa ( 6 0 - p s 0 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 b u m s 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 approxi- mately 10% of the wind load on the building, and, more importantly, it convibutes
-
