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

科技外文文獻(xiàn)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(jì)地震力的確定 地震災(zāi)害具有突發(fā)性，至今可預(yù)報(bào)性很低，給人類(lèi)社會(huì)造成的損失嚴(yán)重，是各類(lèi)自然災(zāi)害中最嚴(yán)重的災(zāi)害之一。我國(guó)根據(jù)現(xiàn)有的科學(xué)水平和經(jīng)濟(jì)條件，對(duì)建筑抗震提出了“三個(gè)水準(zhǔn)”的設(shè)防目標(biāo)，即通常所說(shuō)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(jì)地震力的確定1.1低地震力取值的可行性到二十世紀(jì)八十年代，各國(guó)設(shè)計(jì)規(guī)范都承認(rèn)這樣一個(gè)事實(shí)，就是在地震作用下，結(jié)構(gòu)在真正失效前，有一個(gè)較大的塑性變形能力（結(jié)構(gòu)延性），即結(jié)構(gòu)在一個(gè)較小的地震下可能達(dá)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(jìn)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(jìn)入彈塑性變形的部位增多，先進(jìn)入屈服的部位彈塑性變形也增大。結(jié)構(gòu)通過(guò)這種變形耗散較多的地震傳來(lái)的能量，將其轉(zhuǎn)換成熱能。對(duì)于“設(shè)計(jì)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(jìn)行理解：一方面設(shè)計(jì)地震力低的結(jié)構(gòu)，通過(guò)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(yán)重，阻尼增大，周期比高設(shè)計(jì)地震力的結(jié)構(gòu)增長(zhǎng)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?cè)谠O(shè)計(jì)過(guò)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(gè)小于設(shè)防烈度地震反應(yīng)水準(zhǔn)作為設(shè)計(jì)中取用的地震作用。反過(guò)來(lái)講，若采用的設(shè)計(jì)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(dá)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(gè)問(wèn)題：A．如何在設(shè)防烈度地震作用與設(shè)計(jì)地震力取值之間建立恰當(dāng)?shù)穆?lián)系；B．如何在設(shè)計(jì)地震力與所要求的結(jié)構(gòu)延性建立對(duì)應(yīng)關(guān)系。對(duì)于問(wèn)題A，以N.M.Newmark為代表的眾多學(xué)者認(rèn)為，將設(shè)防烈度地震加速度通過(guò)地震力降低系數(shù)R（中，美等國(guó)）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(jì)加速度，相當(dāng)于賦予結(jié)構(gòu)一個(gè)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(guò)屈服后的非彈性變形來(lái)經(jīng)受更大的地震，實(shí)現(xiàn)“大震不倒”的目標(biāo)。因而，采用低設(shè)計(jì)地震力的關(guān)鍵在于保證結(jié)構(gòu)及構(gòu)件在大震下達(dá)到所需的延性。對(duì)于地震力降低系數(shù)R或結(jié)構(gòu)性能系數(shù)q，各國(guó)設(shè)計(jì)規(guī)范存在略為不同的處理手法，不過(guò)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(jì)所用的地震作用的比值。R或q越大，則要求結(jié)構(gòu)達(dá)到的延性能力越大，R或q越小，則結(jié)構(gòu)需要達(dá)到的延性能力越小。這樣均能實(shí)現(xiàn)“大震不倒”。對(duì)于問(wèn)題B，國(guó)外一般有如下三種設(shè)計(jì)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(shí)際震害表明，這三種方案，從抗震效果和經(jīng)濟(jì)性來(lái)看，都能達(dá)到設(shè)防目標(biāo)。我國(guó)的抗震設(shè)計(jì)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(yùn)動(dòng)加速度來(lái)確定結(jié)構(gòu)的設(shè)計(jì)地震作用，并將它與其他荷載內(nèi)力進(jìn)行組合，進(jìn)行截面設(shè)計(jì)，通過(guò)鋼筋混凝土結(jié)構(gòu)在屈服后的地震反應(yīng)過(guò)程中形成較為有利的耗能機(jī)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(lái)實(shí)現(xiàn)“大震不倒”的目標(biāo)。當(dāng)然，我們還要看到一點(diǎn)，雖然這三個(gè)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(zhǔn)并沒(méi)有明顯提高是明顯不如方案（1）和（2）的。也就是說(shuō)，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(dòng)以波的形式在地下及地表傳播，由于震源特點(diǎn)、斷層機(jī)制、傳播途徑等因素的不確定性，具有很大隨機(jī)性。要想得出地震動(dòng)對(duì)于不同結(jié)構(gòu)有什么不同的反應(yīng)，就需要在地震動(dòng)特性與結(jié)構(gòu)反應(yīng)架起一座橋梁。由于地震動(dòng)反應(yīng)譜的形狀特征反應(yīng)了不同類(lèi)型結(jié)構(gòu)動(dòng)力最大反應(yīng)的特點(diǎn)，所以各工程中一般采用地震影響系數(shù)譜曲線作為計(jì)算地震作用的依據(jù)。我國(guó)的譜曲線綜合考慮了烈度、震中距、場(chǎng)地類(lèi)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(guó)地震動(dòng)參數(shù)區(qū)劃圖，給出了抗震設(shè)防烈度（中震）下的設(shè)計(jì)基本地震加速度。通過(guò)對(duì)震級(jí)、震中距、場(chǎng)地類(lèi)別等因素對(duì)結(jié)構(gòu)反應(yīng)譜的影響，抗震規(guī)范把動(dòng)力放大系數(shù)取為2.25。根據(jù)統(tǒng)計(jì)資料，多遇地震烈度比基本烈度降低約1.55度，相當(dāng)于地震作用降低0.35倍，即地震力