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1、附录2外文资料翻译原文11.7.4Deflection11.7.4.1DeadLoadandCreepDeflectionGlobalverticaldeflectionsofsegmentalbox-girderbridgesduetotheeffectsofdeadloadandpost-tensioningaswellasthelong-termeffectofcreeparenormallypredictedduringthedesignprocessbytheuseofacomputeranalysi
2、sprogram.Thedeflectionsaredependent,toalargeextent,onthemethodofconstructionofthestructure,theageofthesegmentswhenpost-tensioned,andtheageofthestructurewhenotherloadsareapplied.Itcanbeexpected,therefore,thattheactualdeflectionsofthestructurewouldbedifferent
3、fromthatpredictedduringdesignduetochangedassumptions.Thedeflectionsareusuallyrecalculatedbythecontractor’sengineer,basedontheactualconstructionsequence.11.7.4.2CamberRequirementsThepermanentdeflectionofthestructureafterallcreepdeflectionshaveoccurred,normall
4、y10to15yearsafterconstruction,maybeobjectionablefromtheperspectiveofridingcomfortfortheusersorfortheconfidenceofthegeneralpublic.Evenifthereisnostructuralproblemwithaspanwithnoticeablesag,itwillnotinspirepublicconfidence.Forthesereasons,acamberwillnormallyb
5、ecastintothestructuresothatthepermanentdeflectionofthebridgeisnearlyzero.Itmaybepreferabletoignorethecamber,ifitisotherwisenecessarytocastasaginthestructureduringonstruction.11.7.4.3GlobalDeflectionDuetoLiveLoadMostdesigncodeshavealimitontheallowableglobald
6、eflectionofabridgespanduetotheeffectsofliveload.ThepurposeofthislimitistoavoidthenoticeablevibrationfortheuserandminimizetheeffectsofmovingloadiMPact.Whenstructuresareusedbypedestriansaswellasmotorists,thelimitsarefurthertightened.11.7.4.4LocalDeflectionDue
7、toLiveLoadSimilartothelimitsofglobaldeflectionofbridgespans,therearealsolimitationsonthedeflectionofthelocalelementsofthebox-girdercrosssection.Forexample,theAASHTOSpecificationslimitthedeflectionofcantileverarmsduetoserviceliveloadplusiMPactto¹₃ofthecantilev
8、erlength,exceptwherethereispedestrianuse[1].11.7.5Post-TensioningLayout11.7.5.1ExternalPost-TensioningWhilemostconcretebridgescastonfalseworkorprecastbeambridgeshaveutilizedpost-tensioninginductswhicharefullyencased
