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EngineeringStructures28(2006)959–976∗,Myeong-JaeLeeb,Sung-PilChangcaDepartmentofCivilEngineering,MokpoNationalUniversity,61Dorim-ri,Cheonggye-myeon,Muan-gun,Jeonnam,534-729,RepublicofKoreabYooshinEngineeringCorporation,Yoksam-dong,Gangnam-gu,Seoul,135-936,RepublicofKoreacSchoolofCivil,UrbanandGeoSystemsEngineering,SeoulNationalUniversity,San56-1,Shilim-dong,Gwanag-gu,Seoul,151-742,RepublicofKoreaReceived3January2005;receivedinrevisedform24October2005;accepted26October2005Availableonline2February2006AbstractForself-anchoredsuspensionbridges,stiffeninggirdersortrussesshouldbeerectedpriortotheair-spinningofthemaincables.Sincehangersareinstalledbetweenpre-constructedstiffeningtrussesandmaincables,tensioningprocessesarenecessaryforhangerinstallationinthecaseofaself-anchoredsuspensionbridge.Sincehangertensionvariationsinconstructionarequitedependentontheconstructionalplanadopted,thejackingforceandprobablemaximumtensionshouldbepredictedandcomparedintheconstructionaldesignstatesoastodeterminethemostfeasibleandeffectiveplanamongthepossibleoptions.Thisisgenerallydonebytheuseofaso-calledgeometricallynonlinearconstructionstepanalysis.Afiniteelement(FE)analysisprocedure,whichutilizeselasticcatenarycableelementformulationforcontrollingthelengthofthecablemembers,isproposedforthedevelopmentofahangerinstallationplan,inparticularfortheself-anchoredYongjongBridge.Asapre-requisitetoarigorousbackward/forwardconstructionstepanalysis,anunbalancedload-freeFEmodelwasestablishedfollowinganonlinearshape-findinganalysisprocedure.Basedonaseriesofcomparativestudies,aninstallingplan,whichutilizesthesynchronizedjackingofamaximumof80strandjackswiththecombinationofadividedtensioningtechnique,isproposedanditssuccessfulapplicationtotheconstructionoftheYongjongBridgeisdescribed.c2005ElsevierLtd.Allrightsreserved.Keywords:YongjongBridge;Self-anchored;Suspensionbridge;Constructionstep;Hanger;Catenarycableelement1.IntroductionTheYongjongBridgeinKorea[1]isaself-anchoredsuspensionbridge,thestructureofwhichisshowninFig.1.Itwasopenedtotrafficattheendof2000.The550m-longsuspensionbridgehasacenterspanof300mandsidespansof125m.Themaincablesofthebridgetakeathree-dimensionalshape;thatis,thetwomaincablescurvethree-dimensionallyfromthetopofeachtowertotheoutsideofthegirderatthemainspan.Thebridgehasdoubledeckstocarryasix-lanehighwayontheupperdeckandafour-lanehighwayanddualraillinesonthelowerdeck.Theupperdeckofthegirderisasteelboxthatalsofunctionsastheupperchordofthetruss.Oneofthedistinguishingfeaturesoftheself-anchoredsystemisthemaincableanchorage.Thissystemdoesnot∗Correspondingauthor.Tel.:[phone];fax:[phone].E-mailaddress:[e-mail](H.-K.Kim).Fig.1.TheYongjongBridge.0141-0296/$-seefrontmatterc2005ElsevierLtd.Allrightsreserved.doi:10.1016/j.engstruct.2005.10.019960H.-K.Kimetal./EngineeringStructures28(2006)959–976(a)Anearth-anchoredtype.Fig.2.Erectionprocedureofsuspensionbridges.requirethemassiveendanchoragesthataretypicalofearth-anchoredsuspensionbridges.Instead,themaincablesareanchoredtoeachendofstiffeninggirder.Thisdifferenceintheanchoringsystemresultsinconsiderabledifferencesinconstructionprocedure.Forthetypicalearth-anchoredsuspensionbridge,themaincablesandhangersarefirstinstalledusingearthanchorages.Stiffeninggirdersarethensuspendedsuccessivelytothemaincables,asshowninFig.2(a).Thetensionsofmaincablesareverylowbeforetheinstallationofthestiffeninggirders.Astheerectionofstiffeninggirdersproceeds,thetensionofthemaincableconvergestothetargetdead-loadtension.Duringthisinstallingprocess,themaximumhangerforceismainlyinducedbytheproportioneddeadloadimposedoneachhangeranddoesnotappreciablyexceedthefinaldead-loadtension.Consequently,hangertensionsinthistypeofconstructionareoflittleimportanceingeneral.Fortheself-anchoredsuspensionbridge,however,astiffeninggirdermustbeerectedpriortotheair-spinningofmaincablebecauseitfunctionsasasupportingstructureforthemaincables.Temporalpiersare,therefore,necessarytosupportthestiffeninggirderortrussuntiltheconstructionofthesuperstructuresiscompleted,asshowninFig.2(b).Thelastprocessofconstructionconsistsoftransferringdeadloadsfromthetemporalpierstothemaincablesbyinstallinghangers.Atensioningprocessis,therefore,generallyrequiredininstallingeachhangerbetweenthemaincableandthebridgedeckwithapre-determinedunstrainedlength.Inthisprocess,themaximumhangertensionmayreachanunexpectedlyhighlevelandexceedthedesignforceforcertainhangersdependingontheinstallationplanadopted.Eventhoughthemaximumtensionwouldremainquitebelowanallowabletensionofthehangeritself,thecapacityandthetotalnumberofstrandjacksneedtobecarefullydeterminedbyanin-depthanalysisinordertominimizeconstructioncosts,time,andeffort.Ageometricallynonlinearanalysiswouldbepreferableforsolvingthisproblem.Fig.3showsactualpicturesofthemaincableoftheYongjongBridge,duringconstruction.Thesepicturesshowasignificantchangeincableconfigurationbeforeandafterthehangerinst