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1、中文1590字betweentowersincreaseifthenumberofcablesincreaseandtheangleofinclinationofthecablesremainsthesame.B.READINGMATERIALFUTUREOFCABLE-STAYEDBRIDGESIwouldliketobeginwithaviewbackonthedevelopmentofcable-stayedbridgesduringthelast25years.ItstartedwithDischinger'spublicationshortlyaftertheen
2、dofWordWarII.Hepointedmainlytothenecessityofgongingtohighsteelstressesinthestaystoproducestiffnessinthesystem.ThefirstbridgefollowingDischinger'srecommendations,wasbuiltinSweden,designedbyDemag,aGermansteelconstructionfirm,consultedbyDischinger.Thenin1953-54thethreeDuesseldorfbridgeswerede
3、signed,allofthem,withparallelstaycablesbutdifferenttowerarrangements,inordertohaveafamilyofsimilarlyappearingbridges.Thefundamentalconceptoftheseearlydesignswasretainedforoveralmost20years,whichittooktobuiltthem.Welearnedbydetailinganderectingthesebridges.Inthesebridges,onlyafewstaycablesw
4、erechosen;someengineersdesignedtheirbridgeswithevenonlyonestaycable.Thisresultedinlargecableforcescausingdifficultiestoanchorthecablesinthebeamstructure.Heavycrossbeamswerenecessary,theropeshadtobeformed.Togainsufficientspacefortheanchors,adjustmentofcablelengthsbecomesdifficult.Inaddition
5、,thelargedistancebetweenthestaycablescomplicatetheerectionrequiringheavyequipment,auxiliarytrusses,evenauxiliarypierswerenecessarytobuildtheMaracaibobridgeandtheKniebridge.Auxiliarystayeswereneededforcantileveringthebeamplategirdertothenextstaycable.Inaddition,longspansbetweensupportsprovi
6、dedbystaycables,causelargebendingmomentsinthecontinuousbeamandherebyaconsiderabledepthofthegirdersisneeded.Formallofthisexperience,weconcludedforourlaterandfuturedesigns,thata)alargenumberofstaycablesshouldbechoseninawayb)thatoneanchoragesocketcanbeusedtosimplifytheplacingofthecable,c)bysh
7、ortspacingofthecables,bridgegirderbendingmomentsarelowsothatadepthof1to2missufficient,justprovidingadeflectionlinecurvaturesatisfyingtrafficrequirementsandprovidingsafetyagainstbucklinginthedeflectedstage.d)Thespacingofthecablesshouldbesuch,thatnoheavyerection