土木工程外文翻譯-抗震鋼筋混凝土結(jié)構(gòu)設(shè)計(jì)原則

附錄SeismologyCivilEngineeringSEISMICRESISTANTREINFORCEDCONCRETESTRUCTURES-DESIGNPRINCIPLESSUMMARY:Earthquakescauseconsiderableeconomiclosses.Itispossibletominimizetheeconomiclosesbyproperseismicdesign.Inthispaperbasicprinciplesforseismicdesignaresummarized.Therearethreebasicrequirementstobesatisfied;(a)strength,(b)ductilityand(c)stiffness.Inthepaperthesearebrieflydiscussed.Inthesecondpartofthepapertheauthorsummarizeshisviewsonthedamagesobservedinthepastearthquakes.Heconcludesthatmostofthedamageshavebeendueto,(a)badconfiguration,(b)inadequatedetailingand(c)inadequatesupervision.Inthepaperthesearediscussed,pointingoutthecommonmistakesmadeanddamagesobservedasaresultofthesemistakes.Inthelastpartofthepapersomesimplerecommendationsaremadeforproducingseismicresistantreinforcedconcretestructures,emphasizingondetailingandproportioning.KeyWords:Seismicresistance,reinforcedconcrete.1.INTRODUCTIONEveryyearmorethan300000earthquakesoccurontheearth.Manyoftheseareofsmallintensityanddonotcauseanydamagetoourstructures.However,earthquakesoflargerintensityinthevicinityofpopulatedareascauseconsiderabledamageandlossoflife.Itisestimatedthatontheaverage15000peoplehavebeenkilledeachyearthroughouttheworldbecauseofearthquakes.Sinceancienttimesmankindhassoughtwaysandmeansofminimizingthedamagecausedbyearthquakes.Thegreatmastersoftheartofbuildinghavebeenabletobuildstructureswhichhavewithstoodmanysevereearthquakesforcenturies.MagnificentmosquesandbridgesintheMiddleEastbuiltbyourancestorsarestillinservice,Thesemastersdidnotknowseismicanalysis,butwereabletoevaluatepastexperiencewiththeirexcellentengineeringintuitionandjudgement.Mosques,bridgesandschools(Medrese)builtbySinaninIstanbulandEdirnearenotonlybeautiful,butarealsoengineeringmasterpieces.Todaywehavegreatadvantagesascomparedtoourancestors.Wehavemoreexperience,wehavehighlydevelopedanalyticaltoolsandconsiderableexperimentaldata.Itshouldalsobenotedthatcomputersenableustoconsidermorevariablesandseveralalternativesintheanalysis.Themainobjectiveofthispaperistolaydownsomebasicprinciplesforproducingearthquakeresistantreinforcedconcretestructures.Thesearesimpleprinciplesandeasytoapply.Theyhavebeendevelopedinthelightofanalyticalandexperimentalresearchdoneandonobservationsmadefrompastearthquakes.2.BASICPHILOSOPHYANDREQUIREMENTSDesignprinciplescannotbelaiddownunlessthereisawelldefineddesignphilosophy.Thedesignphilosophygenerallyacceptedissummarizedbelow:-Buildingsshouldsuffernostructuraldamageinminor,frequentearthquakes.Normallythereshouldbenononstructuraldamageeither.-Buildingsshouldsuffernoneofminorstructuraldamage(repairable)inoccasionalmoderateearthquakes.-Buildingsshouldnotcollapseinrarelyoccurringmajorearthquakes.Duringsuchearthquakesstructuresarenotexpectedtoremainintheelasticrange.Yieldingofreinforcingstellweillleadtoplastichingesatcriticalsections.Thegeneraldesignphilosophywillnothavemuchpracticaluseunlessdesignrequirementsaredevelopedinparallelwiththisphilosophy.Theauthorbelievesthatthedesignrequirementscanbesummarizedinthreegroups.a.Strengthrequirementsb.Ductilityrequirementsc.Stiffnessrequirements(ordriftcontrol).Thesethreerequirementswillbebrieflydiscussedinthefollowingparagraphs.2.1.StrengthRequirementsMembersinthestructureshouldhaveadequatestrengthtocarrythedesignloadssafely.Sincethedesignersarewellacquaintedwiththisrequirement,itwillnotbediscussedindetail.However,itshouldbepointedoutthatthedesignershouldavoidbrittletypeoffailure,bymakingacapacitydesign(1).ThebasicprinciplesincapacitydesignareillustratedforabeaminFigure1.Ifthedesignsheariscomputedbyplacingtheultimatemomentcapacitiesateachendofthebeam,thedesignercanmakesurethatductileflexuralfailurewilltakeplacepriortoshearfailure.2.2.DuctilityRequirementsIngeneralitisnoteconomicaltodesignR/Cstructurestoremainelasticduringamajorearthquake.Ithasbeendemonstratedthatstructuresdesignedforhorizontalloadsrecommendedinthecodescanonlysurvivestrongearthquakesiftheycanhavetheabilitytodissipateconsiderableamountofenergy.Theenergydissipationisprovidedmainlybylargerotationsatplastichinges.Theenergydissipationbyinelasticdeformationsrequiresthemembersofthestructureandtheirconnectionstopossessadequate"ductility”.Ductilityistheabilitytodissipateasignificantamountofenergythroughinelasticactionunderlargeamplitudedeformations,withoutsubstantialreductionofstrength.Adequateductilitycanbeaccomplishedbyspecifyingminimumrequirementsandbyproperdetailing(2).2.3.StiffnessRequirementsIndesigningabuildingforgravityloads,thedesignershouldconsiderserviceabilityinadditiontoultimatestrength.Inseismicdesign,driftlimitationsimposedmightbeconsideredtobesomekindofaserviceabilityrequirement.However,thedriftlimitationinseismicdesignismoreimportantthantheserviceabilityrequirement.Thelimitingdriftisusuallyexpressedastheratiooftherelativestoreydisplacementtothestoreyheight(interstoreydrift).Excessiveinterstoreydriftleadstoconsiderabledamageinnonstructuralelements.Inmanycasesthecostofreplacingorrepairingofsuchelementsisveryhigh.Excessiveinterstoreydriftcanalsoleadtoverylargesecondordermoments(P-effect)whichcanendangerthesafetyandstabilityofthestructure.Thereforeinterstoreydriftcontrolisconsideredtobeoneofthemostimportantrequirementsinseismicdesign.TherecentMexicoandChileearthquakeshavedemonstratedtheimportanceofthisrequirement(1).InTurkishCodetheinterstoreydriftislimitedto0.0025h,wherehisthestoreyheight.3.LESSONSLEARNEDFROMPASTEARTHQUAKESOurknowledgeinseismicdesignhasdevelopedhasdevelopedasaresultofanalyticalandexperimentalresearchandexperiencegainedfrompastearthquakes.Theauthorbelievesthatlessonslearnedfrompastearthquakeshavebeenthemostimportantsourceamongallothers,becauseearthquakesperformthemostrealisticlaboratorytestsonthebuildings.Theauthorhasreevaluatedthedamagesobservedinearthquakesduringthepast30yearsinTurkey.Thisreevaluationhasrevealedthatmorethan90%ofthedamagescanbeattributedtooneofthefollowingcausesorcombinationsofthese:a.Mistakesmadeinchoosingthebuildingconfiguration(generalconfigurationorthestructuralsystemchosen).b.Inadequatedetalingandproportioningorerrorsmadeindetailing.c.Poorconstructionqualitycausedbyinadequatesupervision.Itisinterestingtonotethatcausesofdamagegroupedintotheabovethreecategoriesseemtoapplytoearthquakedamagesobservedinothercountriesalso.Thesethreecauseswillbediscussedbrieflyintheparagraphstofollow.3.1.BuildingConfigurationSeismicresistanceshouldbeinitiatedatthearchitecturaldesignstage.Ifthegeneralconfigurationchosenbythearchitectiswrong,itisverydifficultandexpensiveforthestructuralengineertomakethebuildingseismicresistant.Asageneralprinciplethefloorplanshouldbeassymmetricalaspossible.Thelengthofwings(T,L,.crossshapedbuildings)causingre-entrantcornersshouldnotbelarge.Ifthelengthofthewingsisnotshort,thentheseshouldbeseparatedfromthemainbuildingbyanexpansionJoint.Symmetryabouttheelevationalaxisisnotassignificantastheplansymmetry.However,abruptchangesinbuildingplanalongtheheightofthebuildingarenotdesirablefromtheseismicresistancepointofview.Setbacksarecommonverticalirregularitiesinbuildinggeometry.Setbackscausediscontinuitiesandabruptchangesinstrengthandstiffness.Theseriousnessofthesetbackeffectdependsontherelativeproportionsandabsolutesizeofseparatepartsofthebuilding.Ingeneralthedesignershouldtrytomakechangesinstrengthandstiffnessalongthebuildingheightassmallaspossible.Asfarasthestructuralsystemisconcerned,onecansetoutsomebasicrulesforbetterseismicresistance.Beforesettingouttheserules,itwouldbeappropriatetoremindtheengineersthatnonstructuralinfillwallswillinfluencetheframebehavioursignificantlyunlessseparatedfromtheframe.Suddenchangesinstiffnessalongtheheightofthebuildingshouldbeavoided.Ifthestiffnessofonestoreyissignificantlysmallerthantheothers(softstorey),prematurefailurecanoccurduetoexcessivelateraldisplacementatthisfloorlevel.AsshowninFigure2,changesinthestoreystiffnesscanbecausednotonlybystructuralelements,butalsobynonstructuralelementssuchasinfillwalls.Twoadjacentbuildingsshouldbeseparatedfromeachotherbyanadequatedistanceinordertoavoidthedamagecausedbypoundingorreciprocalhammeringofthebuildings.Theverticalloadcarryingelementsinafloorshouldbesoproportionedandarrangedthatthecenterofmassandcenterofresistanceshouldnearlycoincide.Ifthesetwocentersareawayfromeachother,theresultingeccentricitycancauseseverefloortorsion,increasingtheshearforcesattheboundaryelementsconsiderably.Torsionisnotonlycreatedbystructuralelements(Figure3b)butcanalsobecreatedbyinfillwallsunlessseparatedfromtheframe,Figure3a.Themaximumshearforcewhichbeactingonacolumncanbefoundbyaddingthemomentcapacities(ultimatemoments)ateachendofthecolumnanddividingbythecolumnlengthFigure4.Thissimplymeansthat,ifthelengthofthecolumnis/5,thenthecolumnwillcarryfivetimesasmuchshear.Forthisreason,shortcolumnsshouldbeavoidedwheneveritispossible,becauseoftheFigure3.dangerofshearfailure.AsillustratedinFigure4,shortcolumnsarecreatedbyeitherstructuralornonstructural(infill)elements.Structureswithflexiblefloormembers(flatplatesorjoistsystemwithshallowbeams)shouldeitherhaverigidcolumnsorshearwalls(orcross-bracing)topreventexcessivedrift.Iftheverticalloadcarryingmembersarenotrigidenough,veryhighsecondordermomentscanresultasshowninFigure5.In1967Adapazariand1985Mexicoearthquakesnumerousfailureshavebeenobservedinbuildingswithflexiblefloorsandslendercolumns.Foramoredetaildiscussiononconfiguration,thereaderisdirectedtoReference2.3.2.ProportioningandDetailingThedimensionsofstructuralmembersnotonlyinfluencethestrength,butalsotheoverallstiffnesofthestructure.Inthelightofexperiencegainedfromthepastearthquakes,theauthorbelievesthattheratioofthesumofthecross-sectionalareasofverticalloadcarryingmemberstothefloorareaisanimportantparameterinseismicresistance.Thisratiowillbecalledthe"DensityRatio".TheauthorhasstudiedthevariationofthisratiointhemonumentalhistoricalbuildingsinIstanbul,whichhavewith-stoodseveralsevereearthquakesduringthepastcenturies.Itwasfoundoutthatthisratiovariedbetween0.2and0.28.Asanexample,thefloorplanoftheSüleymaniye.MosqueisshowninFigure6.Theauthorwouldliketopointoutthesymmetryinthearrangementofloadcarryingmembers.InSüleymaniyethedensityratiowasabout0.24.AnotherinvestigationmadeonmodernreinforcedconcretebuildingsbuiltinseismicareasinTurkeyrevealthattheaveragedensityratioislessthan0.01.Theauthorfindstheratioratherlowandsuggeststhatitshouldbeabout0.015-0.0020.InthecityofVinadelMar,Chiletheaveragedensityratioinreinforcedconcretebuildings(4to23stories)isquitehigh,0.06(3).Thisseemstobeoneofthereasonswhyrelativelysmalldamageoccurredduringthe1985Chileearthquake,whichcreatedquiteaseveregroundmotion.Itshouldbepointedoutthatalthoughdensityratioisaveryimportantparameterforlateralstiffness,therelativestiffnessoffloormembershavealsoasignificantinfluenceonthestiffness.Ductilityrequiredforenergydissipationduringanearthquakeiscloselyrelatedtodetailing.AwelldesignedR/Cstructurecansufferconsiderabledamageifitisnotproperlydetailed.Detailingisanartwhichcannotberealizedunlesstheseismicbehaviourofreinforcedconcreteiswellunderstood.Thebasicprincipleindetailingistoprovidethenecessarystrengthandductilityatcriticalsectionsandjoints.Incuttingthebarsandinmakinglappedsplices,adequateanchoragelengthshouldbeprovided.Thecriticalregionswhereplastichingingisexpectedtooccurshouldbewellconfinedbycloselyspacedhoops.OurexperienceinTurkeyshowsthatinadequatedetailingplayedaveryimportantroleintheearthquakedamageobservedduringthepast30years.Mostofthedamagesattributedtodetailingwereduetoinadequateanchorageorsplicelengthandinadequateconfinement.Basicrulesfordetailingofbeams,columnsandstructuralwallsaresummarizedinFigures7,8and9.3.3.ConstructionTheearthquakewillberesistedbythestructurewhichisactuallybuiltandnotbythestructureshownonthedesigndrawings.Nomatterhowgoodthedesignmethodsusedare,itisnotpossibletoproduceaseismicresistantbuildingunlessthestructureisconstructedinaccordancewiththedesignprojectunderpropersupervision.Inmostofthedevelopingcountriesemphasisisonthedesignstage;qualitycontrolandsupervisionareusuallylookeddownuponandignoredbytheengineer.Theengineershouldrealizethattheimportantrequirementsforseismicresistance,i.e.thestrength,ductilityandstiffnessdependontheactualdimensions,materialqualitiesandreinforcementdetailsaccomplishedonthesite.Poorsupervisionresultsinpoormaterialqualityanderrorsintheplacementofthereinforcingsteel.OurexperienceinTurkeyshowsthatinadequatesupervisionhasbeenthemostimportantcauseofstructuredamageduringpastearthquakes.Inthelightofthesediscussionsonecanconcludethat,forbetterseismicresistance,thefirststepshouldbeinthedirectionofcorrectingthemistakesmadeinthepast.Ifconfiguration,detailingandconstructionsupervisioncannotbeimproved,wellwrittencodesandsophisticatedmethodsofanalyseswillnotbeabletopreventdamageandfailuresinfutureearthquakes.4RECOMMENDATIONSFORDESIGNThemainobjectiveofthissectionistospecifysomesimplerulesforthedesignofordinaryreinforcedconcretestructures.Byordinary,theauthormeansregularstructuresuptosaytenstories.4.1.SummaryofFactsBeforestatingthedesignrules,itwouldbeusefultostatesomebasicfactsabouttheseismicactionandseismicresistanceofreinforcedconcretestructures.-Thecharacteristicsofthegroundmotionexpectedcannotbefullydefined.-Thestructurecannotremainelasticwhensubjectedtoastronggroundmotion.Yieldingwilloccuratdifferentlocationsandmostoftheenergywillbedissipatedatthesesections.-Responseofthestructuredependsnotonlyonthegroundmotion,butalsoonthedynamiccharacteristicsofthestructure,suchasmass,stiffnessanddamping.Forreinforcedconcretestructuresitisverydifficulttoestimatethestiffnessanddamping,becauseofcrackingandtimedependentdeformationswhichhavetakenplacepriortotheearthquake.-Nonstructuralelementsinfluencethebehaivour.-Inordertoanalyzeabuilding,firstasimplephysicalmodeliscreatedbymakingmanysimplifyingassumptions.Theanalysismadeisforthismodelandnotfortherealbuilding.Theassumptionsmadeincreatingthismodelintroduceerrors.-Importantdynamiccharacteristicsuchasmass,stiffnessanddampingdependontheactualdimensionsandmaterialstrengthsobtainedduringconstruction.Thesecanbequitedifferentfromtheonesassumedatthedesignstage.Inthelightofthesefacts,onecaneasilyseethattherearemanyuncertaintiesinvolvedintheseismicdesignofreinforcedconcretebuildings.Theengineershouldbewellawareofthesefactsandshouldnotrelyentirelyonthenumbershehasobtainedfromanalyses.Moresophisticatedandmorecomplicatedmethodsofanalysescaneasilycarrytheengineerawayfromtheactualbehaviourandmakehimaslaveofnumbers.Usuallysimplemethodssupportedbysoundjudgementbasedonbehaviourwillresultinassatisfactoryseismicdesign.4.2.AsimpleApproachSeismicresistancecanbeaccomplishedbyfollowingthebasicstepsgivenbelow:a.Choosingagoodconfigurationb.Makingasatisfactoryanalysis(Staticordynamic)c.Proportioninganddetailingthemembersproperly.d.Constructingthebuildinginaccordancewiththedesignproject,undergoodsupervision.Theauthorbelievesthatforordinaryresidentialorofficebuildingsuptosaytenstories,seismicresistancecanbeobtainedtoagreatextentbyfollowingsomesimplerules.TherulesgivenbelowarebeingusedbyamunicipalityinTurkeyasaguidetodesignersandforcheckingthedesignssubmittedtothismunicipality.Thefirstruleconcernsthedensityratiomentionedpreviously.Forresidentialandofficebuildingsuptotenstories,thesummationofthecross-sectionalareasofverticalloadcarryingmembers(structuralwallsandcolumns)shouldsatisfythefollowingequation.Av0.020Ap(1)Av-summationcross-sectionalareasofallverticalstructuralmembersatthefloor(m2)Ap-planareaatthatfloor(m2)Inadditiontothisrule,thecross-sectionalareaofeachindividualcolumnshouldsatisfythefollowingcondition:Ac0.0015At(n)(2)Howevertheminimumcolumndimensionscannotbelessthan25x25cm.Ac-cross-sectionalareaofthecolumn(m2)At-tributoryareaofthecolumn(m2)n-numberofstoriesaboveThesecondsetofrulesareaboutminimumrequirementsanddetailing.ThesearesummarizedinFigures7,8and9forbeams,columnsandstructuralwalls.Inadditiontothesetwosetsofrules,thedesignershouldchooseareasonableconfigurationandpropersupervisionshouldbeprovidedattheconstructionstage.Ifthesesimplerulesarefollowedandiftherequirementsaresatisfied,mostprobablyadequateseismicresistancewillbeobtainedforthebuildingclassesspecified,evenifalateralloadanalysisisnotperformed.5.CONCLUSIONSTheresponseofreinforcedconcretebuildingsunderseismicactiondependsnotonlyonthenatureofthegroundmotion,butalsoonthedynamiccharacteristicsofthestructure.Duetouncrtaintiesinvolvedinestimatingthenatureofthegroundmotionandthestructuralcharacteristics,onlyapproximateresultscanbeexpectedfromanalyses.Thenumbersobtainedfromanalysesshouldbefilteredbymakinguseofpastexperienceandjudgement.Soundjudgementcanonlybebasedonafirmknowledgeabouttheseismicbehaivourofstructures.Are-evaluationofdamageobservedduringpastearthquakeshasrevealedthatseismicresistancecansignificantlybeimprovedbyfollowingsomesimplerules.Suchsimpleruleshavebeensummarizedinthispaper.REFERENCES1.S?zenMA:"TowardaBehaviourBasedDesignofR/CFramestoResistEarhquakes",9.TechnicalConferenceofTurkishSocietyofCivilEngineers.VI.1,pp.1-44,Ankara,1978.2.ErsoyU:"BasicPrinciplesfortheDesignofSeismicResistantR/CStructures",WorkshoponSeismicDesign,RSS,Amman,Jordan,Nov.1987.3.RiddellR,WoodSL,DeLaLleraJC:"The1985ChileEarthquake",CivilEngineeringStudies,StructuralResearchSeriesNo.534,UILU-ENG.87-2005,UniversityofIllinois,Urbana,April1987.外文資料翻譯土木工程地震學(xué)抗震鋼筋混凝土結(jié)構(gòu)設(shè)計(jì)原則摘要：地震造成相當(dāng)多的經(jīng)濟(jì)損失。通過(guò)適當(dāng)?shù)目拐鹪O(shè)計(jì)將經(jīng)濟(jì)減到最少是可能的。本論文中概述了地震設(shè)計(jì)的基本原則。有三個(gè)基本要求需要滿足：(a)強(qiáng)度，(b)延性和(c)剛度。本論文對(duì)這些進(jìn)行了簡(jiǎn)短的討論。在本論文的第二部份中，作者觀察過(guò)去地震中所造成的破壞并概述了自己的看法。他總結(jié)出大部份的損害可以歸結(jié)于：(a)不規(guī)則的外形，(b)不充分的細(xì)節(jié)設(shè)計(jì)，(c)不充分的監(jiān)督。本論文都對(duì)這些進(jìn)行了討論，作者指出那種常見(jiàn)的錯(cuò)誤和觀察到的破壞就是由這些錯(cuò)誤引起的。在論文的最后一個(gè)部份中作者為鋼筋混凝土結(jié)構(gòu)的抗震設(shè)計(jì)給出一些簡(jiǎn)單的建議，并強(qiáng)調(diào)結(jié)構(gòu)的細(xì)節(jié)設(shè)計(jì)使其成比例。關(guān)鍵字：抗震，鋼筋混凝土。1介紹每年有超過(guò)300000個(gè)地震在地球上發(fā)生。多數(shù)地震強(qiáng)度小而且不會(huì)對(duì)我們的建筑物造成破害。然而，較大強(qiáng)度的地震如果發(fā)生在人口稠密的鄰近區(qū)域，將會(huì)造成大量的破害和人員傷亡。據(jù)估計(jì)全世界每年平均有15000個(gè)人在地震中喪身。自從遠(yuǎn)古時(shí)代以來(lái)，人類已經(jīng)尋找了大量方法和手段把地震引起的破壞減少到最少。建筑大師們已經(jīng)能夠建造出可以在幾個(gè)世紀(jì)中抵抗強(qiáng)烈地震的建筑物。我們的祖先在中東建造的雄偉的清真寺和橋梁至今仍然在使用中，這些大師們不知道如何地震分析，但是他們憑借優(yōu)秀的工程直覺(jué)和判斷力能夠評(píng)估過(guò)去的經(jīng)驗(yàn)。由西納在伊斯坦布爾和Edirne建造的清真寺，橋梁和學(xué)校(Medrese)不僅美麗，而且是工程的杰出作品。今天與我們的祖先相比較，我們有許多優(yōu)勢(shì)。我們有更多經(jīng)驗(yàn)，有高度發(fā)達(dá)的分析工具和相當(dāng)多的實(shí)驗(yàn)數(shù)據(jù)。同樣計(jì)算機(jī)使我們能夠考慮更多的不確定因素和并在分析中采用一些替代方法。本論文的主要目的是為鋼筋混凝土結(jié)構(gòu)的抗震提供一些基本原則。有一些簡(jiǎn)單的并且容易實(shí)施的抗震的基本原則。它們?cè)诘卣鸱治龊蛯?shí)驗(yàn)研究中，和對(duì)過(guò)去地震的觀察報(bào)告中得到不斷的發(fā)展。2基本原理及要求除非定義了很好的設(shè)計(jì)原理，否則不能夠舍棄基本的設(shè)計(jì)原則。普遍接受的設(shè)計(jì)原理可以如下概述：1、建筑物在小型和頻繁的地震中不能有結(jié)構(gòu)破壞，通常也不能有非結(jié)構(gòu)性破壞。2、建筑物在偶然的，中等的地震中不應(yīng)該有結(jié)構(gòu)性破壞（可修復(fù)）。3、建筑物在罕遇地震中不能倒塌。在這種地震中，結(jié)構(gòu)不能作為處于彈性范圍內(nèi)考慮。鋼筋的屈服使得構(gòu)件在關(guān)鍵部位產(chǎn)生塑性鉸。除非設(shè)計(jì)要求超出了設(shè)計(jì)原理，一般的設(shè)計(jì)原理才不會(huì)有實(shí)際意義。作者認(rèn)為設(shè)計(jì)要求可以概括為以下三組：1、強(qiáng)度要求2、延性要求3、剛度要求(位移控制)這三個(gè)要求將會(huì)簡(jiǎn)短地在下列段落中討論。2.1強(qiáng)度要求結(jié)構(gòu)中的構(gòu)件應(yīng)該有足夠的強(qiáng)度來(lái)安全地承受設(shè)計(jì)荷載。由于設(shè)計(jì)者已經(jīng)熟知這一需求,在此不再詳細(xì)討論。然而，需要指出設(shè)計(jì)者應(yīng)該通過(guò)承載力設(shè)計(jì)來(lái)避免構(gòu)件的脆性失效（1）。圖1展示了梁在承載力設(shè)計(jì)時(shí)需要滿足的基本原則。如果設(shè)計(jì)剪力是通過(guò)在梁兩端布置極限彎矩計(jì)算出來(lái)的,設(shè)計(jì)者就能確定彎曲破壞會(huì)在受剪破壞之前發(fā)生。2.2延性要求一般來(lái)說(shuō)把鋼筋混凝土結(jié)構(gòu)設(shè)計(jì)成在大多數(shù)地震中是處于彈性狀態(tài)的，是不經(jīng)濟(jì)的。人們已經(jīng)證明出如果結(jié)構(gòu)有能力消耗大量的能量，并滿足由規(guī)范建議的水平線荷載的建筑物就可以在強(qiáng)烈的地震中幸存下來(lái)。能源的消耗主要是由塑料鉸的大旋轉(zhuǎn)提供。通過(guò)非線性變形的能源消耗需要結(jié)構(gòu)中的構(gòu)件和它們的連接擁有足夠的“延性”。延性是指構(gòu)件在巨大幅度的變形下通過(guò)非線性變形來(lái)消耗能量，并且沒(méi)有巨大的強(qiáng)度損失。足夠的延性可以通過(guò)指定最小量和恰當(dāng)?shù)募?xì)節(jié)設(shè)計(jì)來(lái)完成（2）。2.3剛度要求設(shè)計(jì)一幢建筑物的重力負(fù)荷時(shí)，設(shè)計(jì)者應(yīng)該考慮適用性和極限強(qiáng)度。在抗震設(shè)計(jì)中，強(qiáng)加的極限側(cè)移可以被考慮為對(duì)實(shí)用性的要求。然而，抗震設(shè)計(jì)中的側(cè)移限值比實(shí)用性要求更重要。剛度限值通常是表示為相對(duì)的層間側(cè)移與層高的比值(層間剛度)。過(guò)度的層間側(cè)移將引起非結(jié)構(gòu)構(gòu)件的損害。在多數(shù)情況更換或修理此構(gòu)件是昂貴的。過(guò)度的層間側(cè)移會(huì)引起非常大的第二彎矩重分部(P-效果)，它能危及結(jié)構(gòu)的安全和穩(wěn)定性。因此對(duì)層間位移的控制被認(rèn)為是抗震設(shè)計(jì)中最重要的要求之一。最近墨西哥和智利的地震就證明了這一要求的重要性(1)。在土耳其建筑法規(guī)中，層間位移的限值是0.0025h，這里的h是層高。3從過(guò)去地震學(xué)習(xí)到的經(jīng)驗(yàn)教訓(xùn)對(duì)過(guò)去地震的分析和實(shí)驗(yàn)研究所獲得的經(jīng)驗(yàn)使我們關(guān)于抗震設(shè)計(jì)的知識(shí)不斷得到發(fā)展。作者相信從過(guò)去地震中學(xué)習(xí)到的經(jīng)驗(yàn)教訓(xùn)是所有其它經(jīng)驗(yàn)來(lái)源之中最重要的，因?yàn)榈卣鹪诮ㄖ锷献隽俗瞵F(xiàn)實(shí)的實(shí)驗(yàn)測(cè)試。作者對(duì)土耳其過(guò)去30年期間的地震所造成的破壞進(jìn)行了重新評(píng)估。這次再評(píng)估顯示超過(guò)90%的損害是由下列因素之一或其中某幾個(gè)原因共同導(dǎo)致的：a.建筑物外形的錯(cuò)誤選擇(總體外形或結(jié)構(gòu)的體系選擇)。b.不充分的細(xì)節(jié)設(shè)計(jì)及細(xì)節(jié)設(shè)計(jì)中的比例關(guān)系和錯(cuò)誤。c.不充分的監(jiān)督引起的工程質(zhì)量的不佳。值得一提的是由以上三類造成的破壞似乎同樣適用于在其他國(guó)家觀察到的地震損害。這三種原因?qū)?huì)簡(jiǎn)短地在接下來(lái)的段落中得到討論。3.1建筑物外形建筑物的抗震設(shè)計(jì)應(yīng)該在建筑設(shè)計(jì)階段就開(kāi)始。如果建筑師選擇的總體外形是錯(cuò)誤的，它對(duì)結(jié)構(gòu)工程師來(lái)說(shuō)會(huì)使建筑物抗震變得非常困難和昂貴?？偟脑瓌t是平面設(shè)計(jì)應(yīng)盡可能的對(duì)稱。翼緣的長(zhǎng)度(T型，L型，十字型建筑物)引起的新轉(zhuǎn)角不應(yīng)該太大。如果翼緣的長(zhǎng)度不是短的，那么這些應(yīng)該通過(guò)是擴(kuò)充的連接使其與主體建筑物分開(kāi)。正立面的對(duì)稱性沒(méi)有比平面的對(duì)稱性重要。然而，在建筑設(shè)計(jì)中沿建筑高度的突變從抗震觀點(diǎn)看不可取的。建筑幾何中垂直方向的不規(guī)則是常見(jiàn)的。建筑外形的突變引起強(qiáng)度和剛度的不連續(xù)和突然變化。突變的影響程度跟建筑物的分開(kāi)部分的大小和相對(duì)比例有關(guān)系。大體上設(shè)計(jì)者應(yīng)該使建筑物沿高度方向的強(qiáng)度和剛度變化盡可能小。就結(jié)構(gòu)的體系來(lái)說(shuō)，每個(gè)人都可以展示一些更好的抗震設(shè)計(jì)的基本規(guī)則。在展示這些規(guī)則之前,需要提醒工程師的是非結(jié)構(gòu)的填充墻會(huì)極大影響框架的受力，除非它是獨(dú)立于框架的。沿建筑物高度的剛度突變應(yīng)該避免。如果某一樓層的剛度明顯比其余各層小(軟層)，會(huì)由于該層過(guò)度的側(cè)移導(dǎo)致該層過(guò)早的失效。如圖2所示，樓層的剛度變化不僅與結(jié)構(gòu)構(gòu)件有關(guān)，而且與非結(jié)構(gòu)構(gòu)件比如填充墻有關(guān)。柱子的最大剪力值可以用柱子兩端施加的彎矩容許值(極限彎矩)的和除以層高取得圖4。這就意味著，如果柱子的長(zhǎng)度是五分之一的層高，那么該柱將承受五倍大的剪力值。由于這個(gè)原因?qū)⒁鸺袅ζ茐牡奈ｋU(xiǎn)，所以短柱無(wú)論在哪都應(yīng)該避免。圖4展示了由結(jié)構(gòu)或非結(jié)構(gòu)構(gòu)件引起的短柱。有柔性地板構(gòu)