DOC-土建毕业设计外文翻译-一个未完工的二层预制混凝土结构物的抗震测试-建筑结构

TestsonaHalf-ScaleTwo-StorySeismic-ResistingPrecastConcreteThispaperdescribesexperimentalstudiesontheseismicbehavioranddesignofprecastconcretebuildings.Ahalf-scaletwo-storyprecastconcretebuildingincorporatingadualsystemandrepresentingaparkingstructureinMexicoCitywasinvestigated.Thestructurewastesteduptofailureinalaboratoryundersimulatedseismicloading.Insomeofthebeam-to-columnjoints,thebottomlongitudinalbarsofthebeamwerepurposelyundevelopedduetodimensionalconstraints.Emphasisisgiveninthestudyontheevaluationoftheobservedglobalbehavioroftheteststructure.Thisbehaviorshowedthatthewallsoftheteststructurecontrolledtheforcepathmechanismandsignificantlyreducedthelateraldeformationdemandsintheprecastframes.Seismicdesigncriteriaandcodeimplicationsforprecastconcretestructuresresultingfromthisresearcharediscussed.TheendresultofthisresearchisthatabetterunderstandingofthestructuralbehaviorofthistypeofbuildinghasbeengainedresultsofsimulatedseismicloadtestsofatwostoryprecastconcretebuildingconstructedwithprecastconcreteelementsthatareusedinMexicoaredescribedherein.Thestructuralsystemchosenintheteststructureisthesocalleddualtype,definedasthecombinationofstructuralwallsandbeam-to-columnframes.Connectionsbetweenprecastbeamsandcolumnsintheteststructureareofthe"window"type.Thistypeofconstructionistypicallyusedinlow-andmediumrisebuildingsinwhichcolumnsareconnectedwith"windows"ateachstorylevel.These"windows"containthetopandbottomreinforcement.Fig.1showsthistypeofconstructionforacommercialbuildinginMexicoCity.InmostprecastconcreteframessuchasthoseshowninFig,1,longitudinalbeambottombarsarenotfullydevelopedduetoconstraintsimposedbythedimensionsoffilecolumnsinbeam-to-columnjoints.Inanefforttoovercomethisdeficiency,andasdescribedlater,somepracticingengineersinMexicodesignthesejointsbyprovidinghoopsaroundthehooksofthatreinforcementinordertoachieveitsrequiredcontinuity.However,thispracticeisnotcoveredintheACIBuildingCode(ACI318-02),norintheMexicoCityBuildingCode(MCBC,1993).Partofthisresearchwasdonetoaddressthisissue.TheobjectivesofthisresearchwereIoevaluatetheobservedbehaviorofaprecastconcretestructuresinthelaboratoryandtoproposetheuseofprecaststructuralelementsorprecaststructureswithbothanacceptablelevelofexpectedseismicperformanceandappealingfeaturesfromtheviewpointofconstructionEmphasisisgiveninthispaperontheglobalbehavioroftheteststructure.Inthesecondpartofthisresearchwhichgillbepresentedinacompanionpaper,theobservedbehaviorofconnectionsbetweenprecastelementsintheteststructure,aswellasthebehavioroftheprecastfloorsystemwillbediscussedindetail.Structuralandnonstructuraldamagesobservedinbuildingsduringpastearthquakesthroughouttheworldhaveshowntheimportanceofcontrollinglateraldisplacementinstructurestoreducebuildingdamageduringearth-quakes.Itisalsorelevanttomentionthatthereareseveralcasesofstructuresinmoderateearthquakesinwhichtheobserveddamageinnon-structuralelementsinbuildingswasconsiderableeventhoughthestructuralelementsshowedlittleornodamage.ThisbehaviorisalsorelatedIoexcessivelateraldisplacementdemandsinthestructure.Tominimizeseismicdamageduringearthquakes,theabovediscussionsuggeststheconvenienceofusingastructuralsystemcapableofcontrollinglateraldisplacementsinstructures.Asolutionofthistypeistheso-calleddualsystem.StudiesbyPaulayandPriestley4ontheseismicresponseofdualsystemshaveshownthatthepresenceofwallsreducethedynamicmomentdemandsinstructuralelementsintheframesubsystem.Alsoinconjunctionwithshaketabletestsconductedonacast-in-placereinforcedconcretedualsystem.Bertero5hasshownthepotentialofthedualsystem,inachievingexcellentseismicbehavior[nthisinvestigation,thedualsystemisappliedtothecaseofprecastconcretestructures.DUCTILITYDEMANDINDUALSYSTEMSInordertodevelopabaseforalateranalysisoftheobservedseismicresponseoftheteststructurestudiedinthisprojectasimpleanalyticalmodelisusedtoevaluatethemainfeaturesofductilitydemandsindualsystems.Fig2showstheresultsofasimpleapproachtoanalyzethelateralloadresponseiiiadualsystem.Thelateralloadhasbeennormalizedinsuchamannerthatthecombinationofmaximumlateralresistanceinbothsubsysterni.e.wallsandframes--leadstoalateralresistanceoftheglobalsystemequaltounitybisalsoassumedthatbothsubsystemshavethesamemaximumlateralresistance.Inthefirstcase(Fig2a),itisassumedthatthewallandframesubsystemshaveglobaldisplacementductilitycapacitiesequalto4and2respectively.Inthesecondcase(Fig.2b),theframesubsystemresponseisassumedtobeelastic,andthelateralstiffnessofthewallsubsystemistakentobe4timesthatoftheframesubsystem.AsshowninFig2,thelateraldeformationcompatibilityofthecombinedsystemiscontrolledbythelateraldeformationcapacityofthewallsubsystem.InthefirstcaseFig2akanelastic-plasticenvelopeforthelateralglobalresponseofthedualsystemisassumed,andthecorrespondingdisplacementductility(u)isequalto33.Forthesecondcase(Fig.2b)withanelasticbehavioroftheframesubsystem,thisductilityisequalto25.Thesesimpleexamplesillustratethatintheanalyzedcases,duetothehigherflexibilityintheframesubsystemsascomparedtothoseofthewallsubsystern,inadualsystem,theductilitydemandsintheframesubsystemresultinsmallerductilityvaluesthanthoseofthewallsubsystem.Thisanalyticalfindingwasverifiedinthisstudyfromtheexperimentalstudiesconductedontheteststructure.ThisverificationislaterdiscussedinthepaperItisofinteresttonotethatresultsofthetypeshowninFig.2havebeenalsofoundbyBertero'inshaketabletestsofadualsystem.DESCRIPTIONOFTESTSTRUCTURETheteststructureusedinthisinvestigationisatwo-storyprecastconcretebuilding,representativeofalow-riseparkingstructurelocatedinthehighestseismiczoneofMexicoCity.Theprototypewasconstructedatone-halfscale.Forthesakeofsimplicity,rampsrequiredinaparkingstructurehavenotbeenconsideredintheselectedprototypestructure.Theiruse,requiringlargeopeningsinthefloorsystem,wouldhaverequiredaverycomplexmodelofthefloorsystemforbothlinearandnonlinearanalysisofthestructure.Adetaileddescriptionofthedimensions,materials,designprocedures,andconstructionoftheteststructurecanbefoundelsewhere.6Asummaryofthisinformationisgivenbelow.ThedimensionsandsomecharacteristicsoftheteststructureareshowninFig.3.ThelongitudinalandtransverseareshowninFig3a.Also,theexterior(longitudinal)framecontainingthewall(ColumnLines1and3)aretermedthelateralframe(seeFig,3b),andtheinternal(longitudinal)framewiththesingletee(ColumnLine2)aretermedthecentralframe.DoableteesspanninginthelongitudinaldirectionaresupportedbyL-shapedprecastbeamsinthetransversedirectionasshowninFig3a.Thestructureusesprecastframesandprecaststructuralwalls,thelatterelementsfunctioningasthemainlateralloadresistingsystem.Fig.4showsanearlyphaseoftheconstructionoftheteststructure.Ascanbeseen,the"windows''inthecolumnsandwallsareleftintheseelementsforalaterassemblagewiththeprecastbeams.TheunfasteneddesignbaseshearrequiredbytheMexicoCityBuildingCode(MCBC,1993)2is0.2WT,whereWTisthetotalweightoftheprototypestructure,assumingadeadloadof5,15KPa(108psi)andaliveloadof0.98KPa(20.5psi).TheprototypestructurewasdesignedusingproceduresofelasticanalysesandproportioningrequirementsoftheMCBC,Intheseanalyses,thegrossmomentofinertiaofthemembersinthestructurewasconsideredandrigidoffsets(distancesfromthejointstothefaceofthesupports)wereassumedforallbeamsinthestructureexceptforbeamsinthecentralframe,whichhadsubstandarddetailingaswillbedescribedlatch.Resultsfromtheseanalysesindicatedthatthestructuralwallsintheteststructurewouldtakeabout65percentofthedesignlateralloads.AreviewofthenominallateralresistanceofthestructureusingtheMCBCproceduresshowedthatthisresistingforcewasabout1.3timestherequiredcodelateralresistance(0,2Wr),Thisisoneofseveralfactors,laterdiscussed,thatcontributedtotheover-strengthofthestructure.ThelongitudinalreinforcementinallthestructuralelementsoftheteststructorewasdeformedbarsfromGrade420steel.Table1liststheconcretecompressivecylinderstrengthsfordifferentmembersoftheprototypestructure.Fig.5showstypicalreinforcingdetailsforprecastbeamsspanninginthedirectionoftheappliedlateralload(seeFig.3).Figs.6and7showreinforcingdetailsforthecolumns,andforthestructuralwailsandtheirfoundation,respectively.ItshouldbementionedthattheteststructurewasdesignedwiththerequirementsformoderatelyductilestructuresspecifiedbytheMCBC.Accordingtotheseprovisions,theteststructuredidnotrequirespecialstructuralwallswithboundaryelementssuchasthosespecifiedinChapter21ofAC131802.Theprecasttwo-storycolumnswereconnectedtotheprecastfoundationbyunthreadingtheminagroutedsockettypeconnection.Thereinforcingdetailsofthefoundation,aswellasitsdesignprocedureandbehaviorintheteststructurearediscussedinthecompanionpaper?Taebeam-to-cadmiumjointsinfileteststructurewerecast-in-placetoenablepositioningthelongitudinalreinforcementoftheframingbeams.Thebeamtopreinforcementwasplacedinsumontopoftheprecastbeams.Fig.8showstypicalreinforcingdetailsforthejointsinthedoubleteesofthecentralframe.SincetheseteesandtheirsupportingL-shapedbeamsinAxesAorC(seeFig.3)hadthesamedepth,thehookedbottomlongitudinalbarsinthedoubleteescouldnotpassthroughthefulldepthofthecolumnbecauseofinterferencewiththebottombarsfromfiletransversebeam(seeFig.g).Asaresult,thesehookedbarspossessedonlyabout55percentofthedevelopmentlengthrequiredbyChapter21ofACI318-02.Inanattempttoanchorthesehookedbars,somedesignersinMexicoprovideclosedhoopsaroundthehooks,asshowninFig.8.Theeffectivenessofthisapproachwasalsostudiedinthecompanionpaper.3Beamto-columnjointsinthelateralframesoftheteststructurehadtransversebeamsthatweredeeperthanthelongitudinalbeams.Thismadeitpossibleforthetopandbottombarsofthelongitudinalbeamstopassthroughthefulljoint,and,therefore,thesebarsachievedtheirrequireddevelopmentlength.Cast-in-placetoppingslabsintheteststructurewere30mm(1.18in.)thickandformedthediaphragmsinJanuary-February2005Fig.3.Planandelevationofteststructure:(a)Plan;(b)Lateralframe;(c)Transverseframe.Dimensionsinmm.Note:1mm-0.0394in.thestructuralsystem.Weldedwirereinforcement(WWR)wasusedasreinforcementforthetoppingslabs.TheamountofWWRillthetoppingslabswascontrolledbythetemperatureandshrinkageprovisionsoftheMCBC.whicharesimilartothoseofAC[318-02.Itisofinteresttomentionthattherequirementsforshearstrengthinthediaphragmsgivenbytheseprovisions,whicharesimilartothoseofACI318-89,didnotcontrolthedesign.Awiresizeof6x6in.10/10ledtoareinforcingratioof0.002inthetoppingslab.ThestrengthoftheWWRatyieldandfractureobtainedfromtestswere400and720MPa(58and104ksi),respectively.外文翻译一个未完工的二层预制混凝土结构物的抗震测试这篇文章是关于地震和预制混凝土建筑物设计的试验性的研究。墨西哥市里一个带有双重系统和代表了一个停车场结构的未完工的两层的预制混凝土建筑物被调查研究。这个结构物在实验室里用模拟地震荷载测试，结果失败了。在一些梁和柱的接头处，粱底部的纵筋由于尺寸的限制不能屈服。这项研究所强调的是提高所测试结构物的可观察的综合性能。这种性能表现为所测试结构物的墙控制传力途径而且能显著地减少预制结构所要求的侧向变形。源自于这项研究的预制混凝土结构抗震设计标准和规范细节被讨论。这项研究的最终结果是能更好地理解这种类型的建筑物的已得知的性能。在墨西哥，一个两层的预制混凝土构件建成的预制混凝土建筑物，在其上加上模拟的地震荷载。在这里描述的是其结果。在测试结构物中所选择的结构系统是所谓的双重类型，其定义就是构造墙的结合点以及梁-柱框架。测试结构物中预制梁柱之间的结合是窗型的。这种类型的建设显著地用在低的或中等高建筑物中，在这种建筑中在每一楼层中柱子和窗子连在一起。这些“窗”包含顶部和底部的钢筋。图1所示的是在墨西哥市中这种类型的一个商业建筑物。大多数的预制混凝土结构如图1中所示，纵梁底部的钢筋不能完全屈服。这是由于在梁-柱接头中柱的尺寸限制所造成的。为了尽力克服这种缺陷，正如在后面所描述的，在墨西哥一些工程师尝试着这样设计这些接头，就是通过用箍筋圈住这些钢筋，这样做是为了达到所要求的连续性。然而，这种尝试在ACI建筑规范和MCBC中都没有提到。这些研究的一部分是为了阐述这个观点。这项研究的目的是为了提高在实验室里的预制混凝土结构屋的可观察的性能以及为利用谕旨构件或预制结构建议了一个可接受的期望的抗震性能以及从建设能力的观点所得出的有吸引力的特征。这篇文章中强调的所测试结构物中预制构件间的连接处的可观察的性能以及预制楼层系统的性能将会详细讲述。在过去的地震中，在建筑物中造成的可观察的构造和非构造的破坏显示了通过控制结构的侧向位移来降低由地震造成的建筑物的破坏的重要性。在这里还要提到的是，在中等程度的地震中有一些情况下非结构构件的破坏相当大，尽管构造构件只有一点破坏或根本就没有破坏。这种性能和结构物中所要求的过多的侧向位移有关。为了减少地震所造成的破坏，以上的讨论建议了在结构物中可以方便地使用能控制恻向位移的构造系统。这种类型的解决方法就是所谓的双重系统。Paulay和priestly的关于双重系统的地震反映的研究表明墙的出现降低了框架微系统中结构构件的动力要求。同时，在一个现浇的钢筋混凝土双重系统上所做的摇摆测试显示了双重系统能达到良好的抗震性能的潜力。在这次调查研究中，双重系统应用在预制混凝土构件上。双重系统的柔性要求为了使这个工程所研究的被测试结构物的能观测到的抗震反应的以后的分析打好基础，一个简单的分析模式被用来提高双重系统中主要柔性特征要求。图2所示的是一个简单的分析作用在双重系统侧向荷载反映的结果。侧向荷载从这种方式标准化，将任一系统中最大的侧向抵抗力联合起来。比如，墙和框架导致综合系统的侧向抵抗力。假设任一微系统的总的位移量为4和2。在第二种情况下，框架系统假设为弹性，墙微系统的刚度为框架微系统的4倍。图2所示，联合系统的侧向变形兼容性由墙微系统的侧向变形量控制，在第一种情况下，假设双重系统的总侧向反应有一个塑料封套，相应的位移系数是3.3在第二种情况下，框架微系统在弹性力下，起位移系数是2.5。这些简