學(xué)士畢業(yè)設(shè)計外文翻譯結(jié)構(gòu)設(shè)計地震力的確定

科技外文文獻Determinationofstructuraldesignseismicforces Earthquakeissuddenandhasverylowpredictability,totheseriouslossofhumansociety,isthemostserioustypesofnaturaldisasters,thedisasters.AccordingtothecurrentlevelofscienceinChinaandeconomicconditions,Seismicproposed"threelevels"offortificationgoal,knownas"minorearthquake,theearthquakecanrepair,earthquakedidnotfall."Usuallyaboutasmallearthquake,theearthquake,earthquake,respectivelyreferringtotheprobabilityofexceedancein50years,63%,10%,morethan2to3%oftheearthquake,seismicfortificationintensity,strongearthquake.Astructuredesignedtodeterminetheearthquakeforces1.1ThefeasibilityoflowseismicforcevaluesTwentiethcentury,theeighties,bothcountriesrecognizethedesignofsuchafactthatintheearthquake,structuralfailureintherealbefore,thereisalargeplasticdeformationcapacity(ductility),namelythestructureofasmallerearthquakeinorclosetotheyieldpotentialunderthestate;inlargerearthquakes,thestructureofcertainpositionswillhavemovedintopost-yieldinelasticdeformation,andwiththeseismicforceincreases,thestructureofthesiteintoplasticdeformationincreasedfirstenterthesiteofplasticdeformationofyieldincrease.Dissipationthroughdeformationofthestructureofthisearthquakecamemoreenergytoconvertitintoheat.Forthe"designearthquakeforce-ductile"jointrule,wecanstructuretherelationshipbetweenseismicforceandcarriedouttounderstand:ontheonehandthestructuraldesignoflowseismicforcesbymorenon-elasticdeformationofmoreseismicenergydissipation;othertheonehand,thegreaterthestructureofnon-elasticdeformation,themoreseriouslowerstiffness,dampingincreases,thedesigncycleishighandthestructureofgrowthinseismicforcemorestructurewerealsoreducedtotalseismicforceisalsomore.Thismakesourdesignprocess,withoutreducingtheverticalcomponentofductilitycapacitytoensurethepremise,youcanaccessaleveloflessthanfortificationintensityearthquakesasaccesstotheseismicdesign.Conversely,ifthedesignseismicforcesusingthelowerpartofthepost-yieldstructuralyieldlevelandverticalbearingcapacitydoesnotreducetheneedtomeetunderthepremiseofthelargernon-elasticdeformation,alsoneedtostructureabetterductility.Inthisway,weneedtoaddressthefollowingtwoquestions:A.Howfortificationearthquakeandseismicforcedesignappropriatelinksbetweenthevalues;B.Howtodesignseismicforcesandtoestablishtherequiredcorrespondenceofductility.FortheproblemA,withNMNewmarkrepresentedmanyscholarsbelievethattheaccelerationofseismicfortificationintensityearthquakeforcereductionfactorR(intheUnitedStates)orstructuralpropertiesofcoefficientq(EC,NewZealand,etc.)reductionforthestructuraldesignacceleration,whichisequivalenttogiveasmalleryieldcapacityofthestructure,thestructureofverticalbearingcapacityisnotreducedinthecase,throughnon-elasticdeformationafteryieldingtowithstandearthquakesgreaterrealizationof"earthquakeisnotdown"ofthetarget.Thus,lowdesignseismicforcestructureandthekeytoensuringthenextcomponentintheearthquake,therequiredductility.TheseismicforcereductionfactorRorstructuralperformancecoefficientq,thereisnationaldesignslightlydifferentapproach,butthewholeRorqaretheroleandstructureofseismicfortificationintensitysectiondesignearthquakeusedintheratio.Rorqislarger,theductilitycapacityrequiredtoachievethelargerstructure,Rorqaresmaller,thestructureneedstoachievetheductilitycapacityofthesmaller.Thiscanachieve"earthquakedoesnotfall."FortheproblemB,thefollowingthreekindsofforeigngeneraldesign:(1)higherseismicforces-lowductilityprogram;(2)moderateseismicforces-Mediumductilityprogram;(3)lowerseismicforces-higherductilityprogram.Themainguaranteeofhighseismicforcestructureoftheprogramcapacity,lowseismicforcestructuretoensuretheductilityofthemainprogram.Theactualdamagethatthesethreeprograms,effectivenessandeconomyfromtheseismicpointofview,toachievemaximumsecuritygoals.China'sseismicdesignusedintheprogram(3)thatthelowerseismicforces-highductilityprogramthatusessignificantlylessthanthefortificationofsmallearthquakestodeterminethestructureofthegroundmotionaccelerationofthedesignseismicaction,andloaditwithothercombinationofinternalforcestoconductcross-sectiondesign,reinforcedconcretestructurebytheearthquakeinyieldduringthereactionaftertheformationofmorefavorableenergysector,themajorenergy-consumingpartsofthestructurehasagoodpost-yielddeformationcapacitytoachievethe"earthquakedidnotfall"objectives.Ofcourse,wealsoseethatalthoughthesethreeprogramsisguaranteed,"earthquakedidnotfall,"butsmallearthquakesinimprovingthestructureofthestateunderthetermsoftheprogram(3)onlyimprovetheductilityofthestructureofthelevelstructureyieldlevelsandnosignificantimprovementisevidentastheprogram(1)and(2).Inotherwords,ensurethat"minorearthquake,theearthquakecouldrepair",theprogram(1)and(2)isbetterthantheprogram(3).Intheformofseismicwavepropagationinundergroundandsurface,asthesourcecharacteristics,faultmechanism,transmissionandotherfactorsofuncertainty,hasgreatrandomness.ToarriveatthestructureofgroundmotionfordifferentWhatisthedifferenceintheresponsecharacteristicsofgroundmotionontheneedtobuildbridgeswithstructuralresponse.Asthegroundmotionresponsespectrumreflectstheshapecharacteristicsofdifferenttypesofstructuraldynamicresponsecharacteristicsofthelargest,sotheprojectsgenerallyusetheseismiccoefficientspectrumcurvescalculatedonthebasisearthquake.ConsideringChina'sspectralcurveoftheintensity,epicentraldistance,siteclassification,naturalperiodanddampingratio.UnderthenewChina,thezoningmapshowstheseismicintensity(inshock),thebasicdesignoftheearthquakeacceleration.Bymagnitude,epicenterdistance,siteclassificationandsoontheresponsespectrumofstructures,seismiccodetodynamicmagnificationfactorof2.25.Accordingtostatistics,morethanthebasicintensityofearthquakeintensitydecreaseofabout1.55degrees,equivalentto0.35timeslowerearthquake,orseismicforcereductionfactorof1/0.352.8.Structureisobtainedwhenthedesignofsmallearthquakeacceleration,thevalueoftheratioofgravityshallbeasmallearthquakewhenthemaximumhorizontalseismiccoefficient.Comparedwithothercountries,China'searthquakeforcereductionfactorR2.7~2.8,thevalueofNewZealand"limitedductilityframework"rather(R=3);betweentheEuropeanCommunityandthelowductilityDC"L"(R=2.5)andtheductilityDC"M"(R=3.75)between;thantheUnitedStatesthe"generalframework"(R=3.5)butalsosmallerthansome.FromR'spointofviewalone,itseemsthattheChinesestandardofductilitydemandunderstrongearthquakescomparedwithothercountriesina"moderateductilitystructure"level.ButtheChinesefortificationintensitylevelofpeakgroundmotionaccelerationcoefficientvalue,lowerthaneveryothercountry(seetablebelow).Littledifferencebetweenthedynamicmagnificationfactorinthevicinityof2.25,andtheplatformsectionofourspectralcurvecomparedwithothercountriessmallsectionofsteepdecline,resultinginspectraoflowvaluecomparedwithothercountries,inessence,China'sR=2.8ratherR=5.0intheECabout,soinessence,ouruseofthe"lowerseismicforces-highductility"program.Requiredundertheearthquakeductilitycomparedwithothercountries,shouldbeahighductility.1.2SeismicActionWiththecontinuedmaturationresponsespectrumtheory,allcountriesinthestructureoftheseismicforcestherole,acceptedthebaseshearmethodandthemodalresponsespectrummethodandothermethods.Chinaspecification:Thebottomoftheshearmethodappliedtoaheightnotexceeding40m,inordersheardeformation-basedandhighqualityofthestiffnessdistributionalongthestructure,andtheapproximatesingle-particlestructure.ThetotalseismicforcestructurebytheOK,andthenwrestledthetrianglealongtheheightdistribution,andconsideredthetopoftheearthquakemaybetheculminationofincreasedseismicforcesadditionalconcentration.Moderesponsespectrummethodissuitableformostbuildingstructurescurrentlyavailable.Thevibrationmodecombinationstoconsiderdifferentmodesofallcyclesintheearthquakeresponseofparticipation.Nottoreversethecalculationofthestructure,firstidentifiedthemodalparticlelevelsintheseismicstandardvalue,inaccordancewiththeformulatodeterminethelevelofseismicactioneffects;torsioncouplingonthecalculationofthestructure,itsfloortotaketwoorthogonalhorizontaldisplacementandtherotationangleofthreedegreesoffreedom,todeterminethemodeoftwofloorsinthedirectionofthehorizontaldirectionandangleseismicstandardvalue,pressortodeterminethelevelofearthquakeeffects.Specificationalsoprovidesforspecialirregularbuilding,Abuilding,standardheightrangelistedinTable5.1.2-1high-risebuildings,applicationflexibilityandmoretime-historyanalysismethodundertheadditionalcalculationofearthquake,whenmorethandesirablecurvescalculatedaveragemodalresponsespectrummethodresultsingreatervalue.Anothergeneralelastictimehistoryanalysisresultswillallowthepositiontojudgetheweaklayer.TallBuildingforthe9degreeviewoftheverticalseismicforce,andthebaseshearmethodtotakeasimilarapproach,butthevaluesoftheverticalseismicforcelevelofseismicforcevalueofabout0.57times.Forthelong-periodstructures,earthquakegroundmotionintheaccelerationanddisplacementmayhaveagreaterimpactonthestructure,whilethevibrationresponsespectrummethodofthetheoryUnabletoestimatethisnewspecificationalsoincreasedtheminimumfloorlevelofseismicshearrequirements,seesection5.2.5seismiccode.2.CheckingseismicdeformationThreeseismicfortificationlevelofrequirementstoensurethroughthetwo-stagedesign:themulti-BearingCapacityunderearthquake,constructionofthemainstructureisnotdamaged,non-structuralcomponentswithoutexcessivedamagetoensurethenormaluseofarchitecturalfeatures;buildingunderEarthquakesuffereddamagethemainstructure,butdoesnotcollapse.Checkingseismicdeformationistwo-stagedesignisveryimportantcontenThefirstphaseofdesign,checkingtoelasticdeformationofstorydrift,said.Toensurethestructuralandnonstructuralcomponentsdoesnotcrackorcrackingisnotobvious,toensuretheoverallseismicperformanceofstructures.Checkingnewspecificationincreasestherangeofdeformationonthebendingdominatedbyhigh-risebuildingscandeducttheoveralldeformationofthestructure,becausethispartofthedisplacementofthestructureissoundintermsofdisplacement,butwereadifferentfeelingofcomfort,Checkingforthesecondphaseofdeformationundersevereearthquakes,weaklayerofplasticdeformationofcheckingtosaidplasticlayerdisplacement.Accordingtoexperiencedamage,experimentalresearchandpresentedtheresultsofthelimitdeformationofcomponentsandnodesinthelayerwhenthelimitofdrift,topreventthestructuretooweaklayerofplasticdeformationcausedbystructuralcollapse.Normsdefinedthescopeofchecking,butconsideringthecomplexityofplasticdeformationandthelackofpracticalsoftwarehasdifferentrequirementsfordifferentbuildings.Developmentinthefuturecanbeextendedtocheckingintoalarger,evenbasedondisplacementcontrolmethodtodesignthestructureofthebuildingtomeetcertaintypesofspecialrequirementsonthestructuraldisplacement,toensurethestructuraldisplacementintheacceptablerange.Beexplainedthat,atthisstageofthedisplacementcontrol,andseismicdesignofstructuresunderearthquakeisalsolimitedtoasingleresponse.Howtoeffectivelyconsiderthemanyearthquakesintheearthquakeunderthehighincidenceandcumulativedamageonthestructuraldeformationandseismicperformance,ensuresafetythroughoutthelifeofthestructure,needfurtherstudy.中文翻譯結(jié)構(gòu)設(shè)計地震力的確定 地震災(zāi)害具有突發(fā)性，至今可預(yù)報性很低，給人類社會造成的損失嚴重，是各類自然災(zāi)害中最嚴重的災(zāi)害之一。我國根據(jù)現(xiàn)有的科學(xué)水平和經(jīng)濟條件，對建筑抗震提出了“三個水準”的設(shè)防目標，即通常所說的“小震不壞，中震可修，大震不倒”。通常所講的小震、中震、大震分別指的是50年超越概率為63%，10%，2~3%的多遇地震、設(shè)防烈度地震、罕遇地震。1結(jié)構(gòu)設(shè)計地震力的確定1.1低地震力取值的可行性到二十世紀八十年代，各國設(shè)計規(guī)范都承認這樣一個事實，就是在地震作用下，結(jié)構(gòu)在真正失效前，有一個較大的塑性變形能力（結(jié)構(gòu)延性），即結(jié)構(gòu)在一個較小的地震下可能達到或者接近屈服狀態(tài)；而在較大的地震下，結(jié)構(gòu)的若干部位將陸續(xù)進入屈服后的非彈性變形狀態(tài)，并且隨著地震力的增大，結(jié)構(gòu)中進入彈塑性變形的部位增多，先進入屈服的部位彈塑性變形也增大。結(jié)構(gòu)通過這種變形耗散較多的地震傳來的能量，將其轉(zhuǎn)換成熱能。對于“設(shè)計地震力－延性”聯(lián)合法則，我們可以從地震力和結(jié)構(gòu)相互關(guān)系上進行理解：一方面設(shè)計地震力低的結(jié)構(gòu)，通過更大的非彈性變形耗散掉更多的地震能量；另一方面結(jié)構(gòu)非彈性變形越大，剛度降低越嚴重，阻尼增大，周期比高設(shè)計地震力的結(jié)構(gòu)增長越多，結(jié)構(gòu)受到的總地震力也降低也越多。這就使得我們在設(shè)計過程中，在不降低構(gòu)件豎向承載力保證結(jié)構(gòu)延性的前提下，可以取用一個小于設(shè)防烈度地震反應(yīng)水準作為設(shè)計中取用的地震作用。反過來講，若采用的設(shè)計地震力越低，結(jié)構(gòu)屈服部位在屈服后水平和豎向承載力不降低的前提下需要達到的非彈性變形就越大，也就需要結(jié)構(gòu)有更好的延性性能。這樣，我們就需要解決如下兩個問題：A．如何在設(shè)防烈度地震作用與設(shè)計地震力取值之間建立恰當?shù)穆?lián)系；B．如何在設(shè)計地震力與所要求的結(jié)構(gòu)延性建立對應(yīng)關(guān)系。對于問題A，以N.M.Newmark為代表的眾多學(xué)者認為，將設(shè)防烈度地震加速度通過地震力降低系數(shù)R（中，美等國）或結(jié)構(gòu)性能系數(shù)q（歐共體，新西蘭等）折減為結(jié)構(gòu)設(shè)計加速度，相當于賦予結(jié)構(gòu)一個較小的屈服承載力，結(jié)構(gòu)在豎向承載力不降低的情況下，通過屈服后的非彈性變形來經(jīng)受更大的地震，實現(xiàn)“大震不倒”的目標。因而，采用低設(shè)計地震力的關(guān)鍵在于保證結(jié)構(gòu)及構(gòu)件在大震下達到所需的延性。對于地震力降低系數(shù)R或結(jié)構(gòu)性能系數(shù)q，各國設(shè)計規(guī)范存在略為不同的處理手法，不過總體而言R或q均為設(shè)防烈度地震作用與結(jié)構(gòu)截面設(shè)計所用的地震作用的比值。R或q越大，則要求結(jié)構(gòu)達到的延性能力越大，R或q越小，則結(jié)構(gòu)需要達到的延性能力越小。這樣均能實現(xiàn)“大震不倒”。對于問題B，國外一般有如下三種設(shè)計方案：（1）較高地震力——較低延性方案；（2）中等地震力——中等延性方案；（3）較低地震力——較高延性方案。高地震力方案主要保證結(jié)構(gòu)的承載力，低地震力方案主要保證結(jié)構(gòu)的延性。實際震害表明，這三種方案，從抗震效果和經(jīng)濟性來看，都能達到設(shè)防目標。我國的抗震設(shè)計采用的是方案（3）即較低地震力——較高延性方案，即采用明顯小于設(shè)防烈度的小震地面運動加速度來確定結(jié)構(gòu)的設(shè)計地震作用，并將它與其他荷載內(nèi)力進行組合，進行截面設(shè)計，通過鋼筋混凝土結(jié)構(gòu)在屈服后的地震反應(yīng)過程中形成較為有利的耗能機構(gòu)，使結(jié)構(gòu)主要的耗能部位具有良好的屈服后變形能力來實現(xiàn)“大震不倒”的目標。當然，我們還要看到一點，雖然這三個方案都能保證“大震不倒”，但是在改善結(jié)構(gòu)在中小地震下的性態(tài)方面，方案（3）僅僅提高結(jié)構(gòu)的延性水平而結(jié)構(gòu)的屈服水準并沒有明顯提高是明顯不如方案（1）和（2）的。也就是說，在保證“小震不壞，中震可修”方面，方案（1）和（2）是優(yōu)于方案（3）的。地震動以波的形式在地下及地表傳播，由于震源特點、斷層機制、傳播途徑等因素的不確定性，具有很大隨機性。要想得出地震動對于不同結(jié)構(gòu)有什么不同的反應(yīng)，就需要在地震動特性與結(jié)構(gòu)反應(yīng)架起一座橋梁。由于地震動反應(yīng)譜的形狀特征反應(yīng)了不同類型結(jié)構(gòu)動力最大反應(yīng)的特點，所以各工程中一般采用地震影響系數(shù)譜曲線作為計算地震作用的依據(jù)。我國的譜曲線綜合考慮了烈度、震中距、場地類別、結(jié)構(gòu)自振周期和阻尼比的影響。根據(jù)新修訂的中國地震動參數(shù)區(qū)劃圖，給出了抗震設(shè)防烈度（中震）下的設(shè)計基本地震加速度。通過對震級、震中距、場地類別等因素對結(jié)構(gòu)反應(yīng)譜的影響，抗震規(guī)范把動力放大系數(shù)取為2.25。根據(jù)統(tǒng)計資料，多遇地震烈度比基本烈度降低約1.55度，相當于地震作用降低0.35倍，即地震力