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1、中文1590字betweentowersincreaseifthenumberofcablesincreaseandtheangleofinclinationofthecablesremainsthesame.B.READINGMATERIALFUTUREOFCABLE-STAYEDBRIDGESIwouldliketobeginwithaviewbackonthedevelopmentofcable-stayedbridgesduringthelast25years.ItstartedwithDischinger'sp
2、ublicationshortlyaftertheendofWordWarII.Hepointedmainlytothenecessityofgongingtohighsteelstressesinthestaystoproducestiffnessinthesystem.ThefirstbridgefollowingDischinger'srecommendations,wasbuiltinSweden,designedbyDemag,aGermansteelconstructionfirm,consultedbyDi
3、schinger.Thenin1953-54thethreeDuesseldorfbridgesweredesigned,allofthem,withparallelstaycablesbutdifferenttowerarrangements,inordertohaveafamilyofsimilarlyappearingbridges.Thefundamentalconceptoftheseearlydesignswasretainedforoveralmost20years,whichittooktobuiltth
4、em.Welearnedbydetailinganderectingthesebridges.Inthesebridges,onlyafewstaycableswerechosen;someengineersdesignedtheirbridgeswithevenonlyonestaycable.Thisresultedinlargecableforcescausingdifficultiestoanchorthecablesinthebeamstructure.Heavycrossbeamswerenecessary,
5、theropeshadtobeformed.Togainsufficientspacefortheanchors,adjustmentofcablelengthsbecomesdifficult.Inaddition,thelargedistancebetweenthestaycablescomplicatetheerectionrequiringheavyequipment,auxiliarytrusses,evenauxiliarypierswerenecessarytobuildtheMaracaibobridge
6、andtheKniebridge.Auxiliarystayeswereneededforcantileveringthebeamplategirdertothenextstaycable.Inaddition,longspansbetweensupportsprovidedbystaycables,causelargebendingmomentsinthecontinuousbeamandherebyaconsiderabledepthofthegirdersisneeded.Formallofthisexperien
7、ce,weconcludedforourlaterandfuturedesigns,thata)alargenumberofstaycablesshouldbechoseninawayb)thatoneanchoragesocketcanbeusedtosimplifytheplacingofthecable,c)byshortspacingofthecables,bridgegirderbendingmomentsarelowsothatadepthof1to2missufficient,justprovidingad
8、eflectionlinecurvaturesatisfyingtrafficrequirementsandprovidingsafetyagainstbucklinginthedeflectedstage.d)Thespacingofthecablesshouldbesuch,thatnoheavyerection