文献翻译-水工建筑物-重力坝

Chapter5StaticandDynamicStressAnalysis第五章静态和动态应力分析5-1.StressAnalysis5-1.应力分析a.General.(1)Astressanalysisofgravitydamsisperformedtodeterminethemagnitudeanddistributionofstressesthroughoutthestructureforstaticanddynamicloadconditionsandtoinvestigatethestructuraladequacyofthesubstructanceandfoundation.LoadconditionsusuallyinvestigatedareoutlinedinChapter4.(2)Gravitydamstressesareanalyzedbyeitherapproximatesimplifiedmethodsorthefiniteelementmethoddependingontherefinementrequiredfortheparticularlevelofdesignandthetypeandconfigurationofthedam.Forpreliminarydesigns,simplifiedmethodsusingcantileverbeammodelsfortwo-dimensionalanalysisorthetrialloadtwistmethodforthree-dimensionalanalysisareappropriateasdescribedintheUSBureauofReclamation(USBR),“DesignofGravityDams”(1976).Thefiniteelementmethodisordinarilyusedforthefeatureandfinaldesignstagesifamoreexactstressinvestigationisrequired.a.普通方法(1)重力坝的应力分析是用以确定在静态和动态荷载作用下结构的应力分布和大小情况以及验证下部和基础的结构强度，荷载条件通常在第四章作了概述。(2)重力坝的应力分析通过基于满足坝体类型、构造和设计精度要求的近似的简化方法或有限单元法。初步设计时，根据美国垦务局（USBR）颁布的“重力坝设计规范（1976）”，可以使用二维的悬臂梁模型或者三维的模型试验的简化方法。有限单元法通常用于对应力精度要求更高的详细和最终设计阶段。b.Finiteelementanalysis.(1)Finiteelementmodelsareusedforlinearelasticstaticanddynamicanalysesandfornonlinearanalysesthataccountforinteractionofthedamandfoundation.Thefiniteelementmethodprovidesthecapabilityofmodelingcomplexgeometriesandwidevariationsinmaterialproperties.Thestressesatcorners,aroundopenings,andintensionzonescanbeapproximatedwithafiniteelementmodel.Itcanmodelconcretethermalbehaviorandcouplethermalstresseswithotherloads.Animportantadvantageofthismethodisthatcomplicatedfoundationsinvolvingvariousmaterials,weakjointsonseams,andfracturingcanbereadilymodeled.SpecialpurposecomputerprogramsdesignedspecificallyforanalysisofconcretegravitydamsareCG-DAMS(Anatech1993),whichperformsstatic,dynamic,andnonlinearanalysisandincludesasmearedcrackmodel,andMERLIN(Saouma1994),whichincludesadiscretecrackingfracturemechanicsmodel.b.有限元分析(1)有限元模型用于线性弹性的静态和动态分析以及坝体与基础相互影响的非线性分析。有限元方法具有模拟具有复杂几何形状和不同材料性能的能力。角落处，开口处和有张力处的应力可以用有限元模型来近似。它可以模拟混凝土的热行为和由其他荷载引起的温度应力。此方法的重要优点是对于涉及各种材料的复杂的基础，接缝薄弱处和断裂面能很容易模拟。专门设计用来对混泥土重力坝分析的专用计算机程序是CG-DAMS（Anatech1993年），它执行静态，动态和非线性分析，并包括一个弥散裂缝模型，梅兰（萨乌马1994年），其中包括离散裂缝断裂力学模型。(2)Two-dimensional,finiteelementanalysisisgenerallyappropriateforconcretegravitydams.Thedesignershouldbeawarethatactualstructureresponseisthree-dimensionalandshouldreviewtheanalyticalandrealisticresultstoassurethatthetwo-dimensionapproximationisacceptableandrealistic.Forlongconventionalconcretedamswithtransversecontractionjointsandwithoutkeyedjoints,atwo-dimensionalanalysisshouldbereasonablycorrect.Structureslocatedinnarrowvalleysbetweensteepabutmentsanddamswithvaryingrockmoduliwhichvaryacrossthevalleyareconditionsthatnecessitatethree-dimensionalmodeling.(2)二维的有限元分析一般用于混凝土重力坝。但是设计者应该知道，实际的结构响应是三维的，应审查理论值和真实值以保证这二维近似方法是合理和有效的。对于较长的并设有横缝的常规混凝土大坝，二维的分析应是相当正确的。当结构位于陡峭的桥台之间的狭窄山谷和大坝在各处有不同的岩石模量时则需要使用三维建模。(3)ThespecialpurposeprogramsEarthquakeAnalysisofGravityDamsincludingHydrodynamicInteraction(EADHI)(ChakrabartiandChopra1973)andEarthquakeResponseofConcreteGravityDamsIncludingHydrodynamicandFoundationInteractionEffects(EAGD84)(Chopra,Chakrabarti,andGupta1980)areavailableformodelingthedynamicresponseoflineartwo-dimensionalstructures.Bothprogramsuseaccelerationtimerecordsfordynamicinput.TheprogramSDOFDAMisatwo-dimensionalfiniteelementmodel(ColeandCheek1986)thatcomputesthehydrodynamicloadingusingChopra’ssimplifiedprocedure.ThefiniteelementprogramssuchasGTSTRUDL,SAP,ANSYS,ADINA,andABAQUSprovidegeneralcapabilitiesformodelingstaticanddynamicresponses.(3)一些专用的程序如重力坝地震分析及水动力作用（EADHI）（查克拉巴蒂和乔普拉1973）、流体作用下的混凝土重力坝的地震响应分析和地基交互影响（EAGD84）（乔普拉，查克拉巴蒂，和Gupta1980年）可用于模拟线性二维结构的动力响应。这两个程序都对与动态输入使用加速度时间记录。SDOFDAM程序是用乔普拉简化程序计算水动力荷载的一个二维有限元模型。一些有限元程序如GTSTRUDL,SAP,ANSYS,ADINA,和ABAQUS提供了模拟静态和动态响应的能力。5-2.DynamicAnalysisThestructuralanalysisforearthquakeloadingsconsistsoftwoparts:anapproximateresultantlocationandslidingstabilityanalysisusinganappropriateseismiccoefficient(seeChapter4)andadynamicinternalstressanalysisusingsite-dependentearthquakegroundmotionsifthefollowingconditionsexist:5-2动态分析地震荷载的结构分析包括两部分：一个使用适当的抗震系数（见第4章）的位移和抗滑稳定的近似结果和一个满足下列条件的基于地震动的动态内应力分析：a.Thedamis100feetormoreinheightandthepeakgroundacceleration(PGA)atthesiteisgreaterthan0.2gforthemaximumcredibleearthquake.a.大坝高100英尺以上以及一点对于地震幅度的峰值加速度（PGA）大于0.2g。b.Thedamislessthan100feethighandthePGAatthesiteisgreaterthan0.4gforthemaximumcredibleearthquake.b.大坝高度低于100英尺且一点相对于地震幅度的峰值加速度PGA大于0.4g。c.Therearegatedspillwaymonoliths,wideroadways,intakestructures,orothermonolithsofunusualshapeorgeometry.c.有门控泄洪坝段，宽的通道，进水口，或其他有不寻常的几何形状的坝段。d.Thedamisinaweakenedconditionbecauseofaccident,aging,ordeterioration.Therequirementsforadynamicstressanalysisinthiscasewillbedecidedonaproject-by-projectbasisinconsultantandapprovedbyCECW-ED.d.大坝由于意外情况，老化，或恶化而处于性能衰减的状况。在这种情况下的动态应力分析的要求将决定于专家的且被CECW-ED认可的项目标准。5-3.DynamicAnalysisProcessTheprocedureforperformingadynamicanalysisincludethefollowing:a.Reviewthegeology,seismology,andcontemporarytectonic