土木工程专业英语 教学课件 作者 陈瑛 4.7.Fundamentals of Prestressing.ppt

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1、4.7FundamentalsofPrestressingWhatisPrestess?PrincipleofPrestressingThefunctionofprestressingistoplacetheconcretestructureundercompressioninthoseregionswhereloadcausestensilestress,thereforetoreduceoreliminatecrackingandproducedurableconcretestructures.Co

2、mparisonofReinforcedandPrestressedConcreteBeamsPost-TensioningOperationtendonductanchorjackanchorcastingofconcretetensioningoftendoninstallingoftendonhydraulicjackinstallingofhydraulicjackAnchoragingofthetendonatthestretchingend&Groutingtendonelongatesel

3、asticallyTendonsmadeupofstrandsaresecuredbysteelwedgesthatgripeachstrandandseatfirmlyinawedgeplate锚垫板.Thewedgeplateitselfcarriesallthestrandsandbearsonasteelanchorage.Post-TensioningOperationTheanchoragemaybeasimplesteelbearingplateormaybeaspecialcasting

4、withtwoorthreeconcentricbearingsurfacesthattransferthetendonforcetotheconcrete.Post-TensioningOperationBartendonsareusuallythreadedandanchoredbymeansofsphericalnutsthatbearagainstasquareorrectangularbearingplatecastintotheconcrete.镀锌铁皮预应力波纹管塑料波纹管Post-Ten

5、sioningOperationTheductorsheathingthathousestheprestressingsteelprovidesonelayerofcorrosionprotection.Post-TensioningOperationAtendonwithaductthatcontainsmultiplepiecesofprestressingsteelstrandiscommonlycalledamultistrandtendon多绞线,andatendoninwhichasingl

6、eprestressingsteelstrandiscoveredinaplasticsheathingiscommonlyreferredtoasamonostrandtendon单绞线Post-TensioningOperationInsidetheductorsheathing,theprestressingsteeliscoveredinaprotectivecoatingthatprovidesanotherlevelofcorrosionprotection.Thiscoatingcanbe

7、aspeciallyformulatedtypeofgrease,oritcanbeaspeciallydesignedtypeofgrout.Post-TensioningOperationWhengreaseisused,theprestressingsteelispermanentlyfreetomoverelativetothesheathingandthetendonisreferredtoasanunbondedtendon无粘结预应力筋ThePrestressingForceistrans

8、ferredtotheConcretethroughtheanchorageONLYWhengroutisused,thesteelispermanentlybondedtothesheathingandisreferredtoasabondedtendon有粘结预应力筋.Pre-TensioningInpre-tensioningsystem,thehigh-strengthsteeltendonsarepulledbetweentwoe