建筑外文翻译超高层建筑结构横向风荷载效应.docx

建筑外文翻译超高层建筑结构横向风荷载效应.docx

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建筑外文翻译超高层建筑结构横向风荷载效应

中文3876字

本科毕业设计外文翻译

超高层建筑结构横向风荷载效应

院（系、部）名称：

城市建设学院

专业名称：

土木工程

学生姓名：

***

学生学号：

**********

指导教师：

2012年12月25日

Across-windloadsandeffectsofsuper-tallbuildingsand

Structures

Abstract

Across-windloadsandeffectshavebecomeincreasinglyimportantfactorsinthestructuraldesignofsuper-tallbuildingsandstructureswithincreasingheight.Across-windloadsandeffectsoftallbuildingsandstructuresarebelievedtobeexcitedbyinflowturbulence,wake,andinflow-structureinteraction,whichareverycomplicated.Althoughresearchershavebeenfocusingontheproblemforover30years,thedatabaseofacross-windloadsandeffectsandthecomputationmethodsofequivalentstaticwindloadshavenotyetbeendeveloped,mostcountrieshavingnorelatedrulesintheloadcodes.Researchresultsontheacross-windeffectsoftallbuildingsandstructuresmainlyinvolvethedeterminationofacross-windaerodynamicforcesandacross-windaerodynamicdamping,developmentoftheirdatabases,theoreticalmethodsofequivalentstaticwindloads,andsoon.Inthispaperwefirstreviewthecurrentresearchonacross-windloadsandeffectsofsuper-tallbuildingsandstructuresbothathomeandabroad.Thenwepresenttheresultsofourstudy.Finally,weillustrateacasestudyinwhichourresearchresultsareappliedtoatypicalsuper-tallstructure.

Introduction

Withthedevelopmentofscienceandtechnology,structuresarebecominglarger,longer,taller,andmoresensitivetostrongwind.Thus,windengineeringresearchersarefacingwithmorenewchallenges,evenproblemstheyarecurrentlyunawareof.Forexample,theconstructionofsupertallbuildingsisnowprevalentaroundtheworld.TheChicagoSearsTowerwithaheightof443mhaskepttherecordoftheworld’stallestbuildingfor26yearsnow.Dozensofsuper-tallbuildingswithheightsofover400maresettobeconstructed.BurjDubaiTowerwithaheightof828mhasjustbeencompleted.Indevelopedcountries,thereareevenproposalstobuild“citiesintheair”withthousandsofmetersofmagnitude.Withtheincreaseinheightanduseoflightandhigh-strengthmaterials,wind-induceddynamicresponses,especiallyacross-winddynamicresponsesofsuper-tallbuildingsandstructureswithlowdamping,willbecomemorenotable.Hence,strongwindloadwillbecomeanimportantcontrolfactorindesigningsafesuper-tallbuildingsandstructures.

Davenportinitiallyintroducedstochasticconceptsandmethodsintowind-resistantstudyonalong-windloadsandeffectsofbuildingsandotherstructures.Afterward,researchersdevelopedrelatedtheoriesandmethods,andthemainresearchresultshavealreadybeenreflectedintheloadcodesofsomecountriesforthedesignofbuildingsandstructures.Formodernsuper-tallbuildingsandstructures,across-windloadsandeffectsmaysurpassalong-windones.Althoughresearchershavebeenfocusingonthecomplexproblemforover30yearsnow,thewidelyaccepteddata-baseofacross-windloadsandcomputationmethodsofequivalentstaticwindloadshavenotbeenformedyet.Onlyafewcountrieshaveaccordinglyadoptedtherelatedcon-tentsandprovisionsintheircodes.

Therefore,studyingacross-windvibrationandtheequivalentstaticwindloadsofsuper-tallbuildingsandstructuresisofgreattheoreticalsignificanceandpracticalvalueinthefieldofstructuraldesignofsuper-tallbuildingsandstructures.Thecurrentpaperthusreviewstheresearch

situationofacross-windloadsandeffectsofsuper-tallbuildingsandstructuresbothathomeandabroad.Then,theresearchresultsgivenbyusarepresented.Finally,acasestudyofacross-windloadsandeffectsofatypicalsuper-tallstructureisillustrated.

Mechanismofacross-windloadsandeffects

Previousresearchesfocusedmainlyonthemechanismofacross-windload.Kwokpointedoutthatacross-windexcitationcomesfromwake,inflowturbulence,andwind-structureinteractioneffect,whichcouldberecognizedasaerodynamicdamping.Solariattributedtheacross-windloadtoacross-windturbulenceandwakeexcitations,consideringwakeasthemainexcitation.Islametal.andKareemclaimedthatacross-windresponsesareinducedbylateraluniformpressurefluctuationduetoseparationshearlayerandwakefluctuation.Currently,themechanismofacross-windloadontallbuildingsandstructureshasbeenrecognizedasinflowturbulenceexcitation,wakeexcitation,andaeroelasticeffect.Inflowturbulenceandwakeexcitationareessentiallytheexternalaerodynamicforce,whichiscollectivelyreferredtointhepresentpaperasaerodynamicforce.Meanwhile,aeroelasticeffectcanbetreatedasaerodynamicdamping.Across-windaero-dynamicforcenolongerconformstoquasi-steadyassumptionasthealong-windone;thus,theacross-windforcespectracannotbedirectlyexpressedasafunctionofinflowfluctuatingwindvelocityspectra.Windtunneltesttechniqueforunsteadywindpressuresorforcesispresentlyamaintoolforstudyingacross-windaerodynamicforces.Thewindtunnelexperimenttechniquemainlyinvolvestheaero-elasticbuildingmodelexperimenttechnique,highfrequencyforcebalancetechnique,andrigidmodelexperimenttechniqueformulti-pointpressuremeasurement.Usingdataofacross-windexternalaerodynamicforceandacross-windaerodynamicdamping,across-windresponsesandtheequivalentstaticwindloadofbuildingsandstructurescanbecomputedforthestructuraldesignofsuper-tallbuildingsandstructures.

Across-windaerodynamicforce

Asstatedabove,theacross-windaerodynamicforcecanbeobtainedbasicallythroughthefollowingchannels:

identifyingacross-windaerodynamicforcefromacross-windresponsesofanaeroelasticbuildingmodelinawindtunnel;obtainingacross-windaerodynamicforcethroughspatialintegrationofwindpressureonrigidmodels;obtaininggeneralizedaerodynamicforcedirectlyfrommeasuringbasebendingmomentusinghighfrequencyforcebalancetechnique.

Identificationofacross-windaerodynamicforcefromdynamicresponsesofaeroelasticbuildingmodel.

Thismethodemploysacross-winddynamicresponsesoftheaeroelasticbuildingmodel,combiningthedynamiccharacteristicsofthemodeltoidentifyacross-windaerodynamicforce.MelbourneandCheungperformedaeroelasticmodelwindtunneltestsonaseriesofcircular,square,hexagon,polygonwitheightangles,squarewithreentrantanglesandfillets,andtallorcylindricalstructureswithsectionscontractingalongheight.However,furtherstudiesshowedthatacross-windaerodynamicdampingforceandaerodynamicforcemixedtogethermakeitdifficulttoextractaerodynamicdampingforceaccurately.Assuch,themethodhasbeenseldomused.

Windpressureintegrationmethod.

Researchershaverecommendedwindpressureintegrationtoobtainmoreaccuratelytheacross-windaerodynamicforcesontallbuildings.Islametal.adoptedthismethodtoobtainacross-windaerodynamicforcesontallbuildingsandstructures.Chengetal.experimentallystudiedacross-windaerodynamicforcesoftypicalbuildingsunderdifferentwindfieldconditionsandderivedempiricalformulasforthepowerspectrumdensityoftheacross-windaerodynamicforcereflectingtheeffectsofturbulentintensityandturbulentscale.TurbulentintensitywasfoundtowidenthebandwidthofPSDoftheacross-windaerodynamicforceandreducethepeakvalue.However,turbulentintensitywasdeterminedtohavealmostnoeffectsontotalenergy.Thus,researchershaverecognizedthequantitativerulesofvariationofacross-windaerodynamicforcewithwindconditiontosomeextent.Liangetal.examinedacross-windaerodynamicforcesontypicalrectangularbuildingsinaboundarylayerwindtunnelusingthismethod,thusproposingempiricalformulasforPSDofacross-windaerodynamicforcesoftallrectangularbuildingsandananalyticalmodelforacross-winddynamicresponses.YeandZhangdecomposedacross-windturbulenceexcitationandvortexsheddingexcitationinacross-windaerodynamicforcesontypicalsuper-tallbuildings.Theresultsshowedthattheacross-windturbulencecontributedmuchlesstoacross-windaerodynamicforcethanthewakeexcitation.Basedonalargenumberofresults,wederivedPSDformulasfortheacross-windturbulenceexcitationandthewakeexcitation,andfurtherderivedanewformulafortheacross-windaerodynamicforce.Thefirst-andhigher-modegeneralizedacross-windaerodynamicforcescanbecalculatedthroughtheintegrationofpressuredistributiononrigidbuildingmodels,whichisanimportantadvantageofthismethod.However,giventheneedforalargenumberofpressuretapsforverylarge-scalestructuresinthiskindofmethod,synchronouspressuremeasurementsaredifficulttomake.Moreover,forbuildingsandstructureswithcomplexconfigurations,accuratewindpressuredistributionandaerodynamicforcearedifficulttoobtainusingthiskindofmethod.

Highfrequencyforcebalancetechnique.

Comparedwiththepressuremeasuringtechnique,highfrequencyforcebalancetechniquehasitsuniqueadvantageforobtainingtotalaerodynamicforces.Thetestanddataanalysisproceduresarebothverysimple;hence,thistechniqueiscommonlyusedforselectionstudiesonarchitecturalappearanceintheinitialdesignstageofsuper-tallbuildingsandstructures.Currently,thistechniqueiswidelyusedfortotalwindloadsactingonsuper-tallbuildingsandstructures,andfordynamicresponsecomputationaswell.Thehighfrequencyforcebalancetechniquehasbeengraduallydevelopedsincethe1970s.Cermaketal.werethefirsttousethistechniqueforbuildingmodelmeasurement.