桥梁设计外文翻译

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1、附录2外文资料翻译原文11.7.4Deflection11.7.4.1DeadLoadandCreepDeflectionGlobalverticaldeflectionsofsegmentalbox-girderbridgesduetotheeffectsofdeadloadandpost-tensioningaswellasthelong-termeffectofcreeparenormallypredictedduringthedesignprocessbytheuseofacomputeranalysisprogram.Thedeflectionsaredepende

2、nt,toalargeextent,onthemethodofconstructionofthestructure,theageofthesegmentswhenpost-tensioned,andtheageofthestructurewhenotherloadsareapplied.Itcanbeexpected,therefore,thattheactualdeflectionsofthestructurewouldbedifferentfromthatpredictedduringdesignduetochangedassumptions.Thedeflectio

3、nsareusuallyrecalculatedbythecontractor’sengineer,basedontheactualconstructionsequence.11.7.4.2CamberRequirementsThepermanentdeflectionofthestructureafterallcreepdeflectionshaveoccurred,normally10to15yearsafterconstruction,maybeobjectionablefromtheperspectiveofridingcomfortfortheusersorfo

4、rtheconfidenceofthegeneralpublic.Evenifthereisnostructuralproblemwithaspanwithnoticeablesag,itwillnotinspirepublicconfidence.Forthesereasons,acamberwillnormallybecastintothestructuresothatthepermanentdeflectionofthebridgeisnearlyzero.Itmaybepreferabletoignorethecamber,ifitisotherwisenecess

5、arytocastasaginthestructureduringonstruction.11.7.4.3GlobalDeflectionDuetoLiveLoadMostdesigncodeshavealimitontheallowableglobaldeflectionofabridgespanduetotheeffectsofliveload.ThepurposeofthislimitistoavoidthenoticeablevibrationfortheuserandminimizetheeffectsofmovingloadiMPact.Whenstructu

6、resareusedbypedestriansaswellasmotorists,thelimitsarefurthertightened.11.7.4.4LocalDeflectionDuetoLiveLoadSimilartothelimitsofglobaldeflectionofbridgespans,therearealsolimitationsonthedeflectionofthelocalelementsofthebox-girdercrosssection.Forexample,theAASHTOSpecificationslimitthedeflection

7、ofcantileverarmsduetoserviceliveloadplusiMPactto¹₃ofthecantileverlength,exceptwherethereispedestrianuse[1].11.7.5Post-TensioningLayout11.7.5.1ExternalPost-TensioningWhilemostconcretebridgescastonfalseworkorprecastbeambridgeshaveutilizedpost-tensioninginductswhicharefullyencased