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1、本科毕业设计外文翻译混凝土桥梁的结构形式院（系、部）名称：专业名称：学生姓名：学生学号：指导教师：TheStructureofConcreteBridgePre-stressedconcretehasprovedtobetechnicallyadvantageous,economicallycompetitive,andestheticallysuperiorbridges,fromveryshortspanstructuresusingstandardcomponentstocable-stayedgirdersandcontinuousboxgirders
2、withclearspansofnearly100aft.Nearlyallconcretebridges,eventhoseofrelativelyshortspan,arenowpre-stressed.Pre-casting,cast-in-placeconstruction,oracombinationofthetwomethodsmaybeused.Bothpre-tensioningandposttensioningareemployed,oftenonthesameproject.IntheUnitedStates,highwaybridgesg
3、enerallymust-meetloading,design,andconstructionrequirementsoftheAASHTOSpecification.Designrequirementsforpedestriancrossingsandbridgesservingotherpurposesmaybeestablishedbylocalorregionalcodesandspecifications.ACICodeprovisionsareoftenincorporatedbyreference.Bridgesspanstoabout100ft
4、oftenconsistofpre-castintegral-deckunits,whichofferlowinitialcost,minimum,maintenance,andfasteasyconstruction,withminimumtrafficinterruption.Suchgirdersaregenerallypre-tensioned.Theunitsareplacedsidebyside,andareoftenpost-tensionedlaterallyatintermediatediaphragmlocations,afterwhich
5、shearkeysbetweenadjacentunitsarefilledwithnon-shrinkingmortar.Forhighwayspans,anasphaltwearingsurfacemaybeapplieddirectlytothetopofthepre-castconcrete.Insomecases,acast-in-placeslabisplacedtoprovidecompositeaction.Thevoidedslabsarecommonlyavailableindepthsfrom15to21in.andwidthsof3to
6、4ft.ForastandardhighwayHS20loading,theyaresuitableforspanstoabout50ft,Standardchannelsectionsareavailableindepthsfrom21to35inavarietyofwidths,andareusedforspansbetweenabout20and60ft.Thehollowboxbeams-andsingle-teegirdersareintendedforlongerspansuptoabout100ft.Formedium-spanhighwaybr
7、idges,toabout120ft,AASHTOstandardIbeamsaregenerallyused.Theyareintendedforusewithacompositecast-in-placeroadwayslab.Suchgirdersoftencombinepre-tensioningofthepre-castmemberwithpost-tensioningofthecompositebeamafterthedeckisplaced.Inanefforttoobtainimprovedeconomy,somestateshaveadopt
8、edmorerefineddesign
