《土木工程專業(yè)英語 第2版》 課件 Unit3 Introduction to Steel Structures；Unit4 Seismic Design

Unit3IntroductiontoSteelStructuresEnglishforCivilEngineering——Teacher:Prof.ZhengLu（SchoolofCivilEngineering,TONGJIUNIVERSITY）Unit3IntroductiontoSteelStructures3.1StructuralDesign（結(jié)構(gòu)設(shè)計(jì)）3.2PrinciplesofDesign（設(shè)計(jì)準(zhǔn)則）3.3HistoricalBackgroundofSteelStructures（鋼結(jié)構(gòu)背景）3.4Loads（荷載）3.4.1DeadLoad（靜荷載）3.4.2LiveLoad（活荷載）3.4.3HighwayLiveLoads（高速公路活荷載）3.4.4Impact（沖擊荷載）3.4.5SnowLoad（雪荷載）3.4.6WindLoad（風(fēng)荷載）3.4.7EarthquakeLoad（地震作用）3.5TypesofStructuralSteelMembers（鋼結(jié)構(gòu)構(gòu)件）3.5.1TensionMembers（受拉構(gòu)件）3.5.2CompressionMembers（受壓構(gòu)件）3.5.3Beams（梁）3.5.4BendingandAxialLoad（壓（拉）彎構(gòu)件）Structuraldesignmaybedefinedasamixtureofartandscience,combiningtheexperiencedengineer’sintuitivefeelingforthebehaviorofastructurewithasoundknowledgeoftheprinciplesofstatics,dynamics,mechanicsofmaterials,andstructuralanalysis,toproduceasafeeconomicalstructurethatwillserveitsintendedpurpose.結(jié)構(gòu)設(shè)計(jì)的定義intuitive直觀的；sound合理的；intended預(yù)期的3.1StructuralDesignUntilabout1850,structuraldesignwaslargelyanartrelyingonintuitiontodeterminethesizeandarrangementofthestructuralelements.Earlyman-madestructuresessentially

conformedtothosewhichcouldalsobeobservedinnature,suchasbeamsandarches.Astheprinciplesgoverningthebehaviorofstructuresandstructuralmaterialshavebecomebetterunderstood,designprocedureshavebecomemorescientific.早期的結(jié)構(gòu)設(shè)計(jì)intuition直覺；

conformedto符合；

essentially基本上；governing控制3.1StructuralDesignComputationsinvolvingscientificprinciplesshouldserveasaguidetodecisionmakingandnotbefollowedblindly.Theartorintuitiveabilityoftheexperiencedengineerisutilizedtomakethedecisions,guidedbythecomputationalresults.結(jié)構(gòu)設(shè)計(jì)的原則isutilizedto利用3.1StructuralDesignDesignisaprocessbywhichanoptimumsolutionisobtained.Inthistexttheconcerniswiththedesignofstructures—inparticular,steelstructures.Inanydesign,certaincriteriamustbeestablishedtoevaluatewhetherornotanoptimumhasbeenachieved.Forastructure,typicalcriteriamaybe(a)minimumcost;(b)minimumweight;(c)minimumconstructiontime;(d)minimumlabor;(e)minimumcostofmanufactureofowner’sproducts;and(f)maximumefficiencyofoperationtoowner.Usuallyseveralcriteriaareinvolved,eachofwhichmayrequireweighting.Observingtheabovepossiblecriteria,itmaybeapparentthatsettingclearlymeasurablecriteria(suchasweightandcost)forestablishinganoptimumfrequentlywillbedifficult,andperhapsimpossible.Inmostpracticalsituations,theevaluationmustbequalitative.設(shè)計(jì)準(zhǔn)則的要求optimum最佳的，最佳效果；criteria原則；manufacture建造；weighting加權(quán)重；qualitative定性的3.2PrinciplesofDesignIfaspecificobjectivecriterioncanbeexpressedmathematically,thenoptimization

techniquesmaybeemployedtoobtainamaximumorminimumfortheobjectivefunction.Optimizationproceduresandtechniquescompriseanentiresubjectthatisoutsidethescopeofthistext.Thecriterionofminimumweightisemphasizedthroughout,underthegeneralassumptionthatminimummaterialrepresentsminimumcost.Othersubjectivecriteriamustbekeptinmind,eventhoughtheintegrationofbehavioralprincipleswithdesignofstructuralsteelelementsinthistextutilizesonlysimpleobjectivecriteria,suchasweightorcost.結(jié)構(gòu)設(shè)計(jì)的優(yōu)化方法criterion標(biāo)準(zhǔn)；optimization

techniques優(yōu)化方法；scope范圍；comprise

包含assumption假定；integration整合；utilize利用3.2PrinciplesofDesignThedesignproceduremaybeconsideredtobecomposedoftwoparts—functionaldesignandstructuralframeworkdesign.Functionaldesignensuresthatintendedresultsareachieved,suchas(a)adequateworkingareasandclearances;(b)properventilationand/orairconditioning;(c)adequatetransportationfacilities,suchaselevators,stairways,andcranesormaterialshandlingequipment;(d)adequatelighting;and(e)aesthetics.設(shè)計(jì)過程包含兩部分——功能設(shè)計(jì)和結(jié)構(gòu)框架設(shè)計(jì)adequate充足的；clearance空隙；ventilation通風(fēng)系統(tǒng)；crane吊車；aesthetics美觀3.2PrinciplesofDesignThestructuralframeworkdesignistheselectionofarrangementandsizesofstructuralelementssothatserviceloadsmaybesafelycarried,anddisplacementsarewithinacceptablelimits.結(jié)構(gòu)框架設(shè)計(jì)3.2PrinciplesofDesignTheiterativedesignproceduremaybeoutlinedasfollows:1.Planning.Establishmentofthefunctionsforwhichthestructuremustserve.Setcriteriaagainstwhichtomeasuretheresultingdesignforbeinganoptimum.2.Preliminarystructuralconfiguration.Arrangementoftheelementstoservethefunctionsinstep1.3.Establishmentoftheloadstobecarried.4.Preliminarymemberselection.Basedonthedecisionsofsteps1,2,and3selectionofthemembersizestosatisfyanobjectivecriterion,suchasleastweightorcost.設(shè)計(jì)過程的具體步驟1—4iterative重復(fù)的；preliminary初步的；configuration配置；satisfy達(dá)到3.2PrinciplesofDesign5.Analysis.Structuralanalysisinvolvingmodelingtheloadsandthestructuralframeworktoobtaininternalforcesandanydesireddeflections.6.Evaluation.Areallstrengthandserviceabilityrequirementssatisfiedandistheresultoptimum?Comparetheresultwithpredeterminedcriteria.7.Redesign.Repetitionofanypartofthesequence1through6foundnecessaryordesirableasaresultofevaluation.Steps1through6representaniterativeprocess.Usuallyinthistextonlysteps3through6willbesubjecttothisiterationsincethestructuralconfigurationandexternalloadingwillbeprescribed.8.Finaldecision.Thedeterminationofwhetherornotanoptimumdesignhasbeenachieved.設(shè)計(jì)過程的具體步驟5—8internalforces內(nèi)力；serviceabilityrequirements使用要求；prescribed規(guī)定3.2PrinciplesofDesignMetalasastructuralmaterialbeganwithcastiron,usedona100-ft(30-m)archspanwhichwasbuiltinEnglandin1777-1779.Anumberofcast-ironbridgeswerebuiltduringtheperiod1780-1820,mostlyarch-shapedwithmaingirdersconsistingofindividualcast-ironpiecesformingbarsortrusses.Castironwasalsousedforchainlinksonsuspensionbridgesuntilabout1840.鑄鐵的應(yīng)用castiron鑄鐵；girder梁；bar條形；truss桁架；chainlinks鎖鏈；suspensionbridges懸索橋3.3HistoricalBackgroundofSteelStructuresThedevelopmentoftheBessemerprocess(1855),theintroductionofabasiclinerintheBessemerconverter(1870),andtheopen-hearthfurnacebroughtwidespreaduseofironoreproductsinbuildingmaterials.Since1890,steelhasreplacedwroughtironastheprincipalmetallicbuildingmaterial.Currently(1989),steelshavingyieldstressesvaryingfrom24,000to100,000poundspersquareinch,psi(165to690megapascals,MPa),andavailableforstructuraluses.金屬材料從鍛鐵向鋼鐵轉(zhuǎn)變Bessemerprocess貝塞麥（轉(zhuǎn)爐）煉鋼法；Bessemerconverter貝氏轉(zhuǎn)爐；open-hearthfurnace平爐；ironore鐵礦石；wroughtiron鍛鐵（熟鐵）3.3HistoricalBackgroundofSteelStructuresTheaccuratedeterminationoftheloadstowhichastructureorstructuralelementwillbesubjectedisnotalwayspredictable.Eveniftheloadsarewellknownatonelocationinastructure,thedistributionofloadfromelementtoelementthroughoutthestructureusuallyrequiresassumptionsandapproximations.Someofthemostcommonkindsofloadsarediscussedinthefollowingsections.荷載概述distribution分布；approximations近似3.4LoadsDeadloadisafixed-positiongravityserviceload,socalledbecauseitactscontinuouslytowardtheearthwhenthestructureisinservice.Theweightofthestructureisconsidereddeadload,aswellasattachmentstothestructuresuchaspipes,electricalconduit,air-conditioningandheatingducts,lightingfixtures,floorcovering,roofcovering,andsuspendedceilings;thatis,allitemsthatremainthroughoutthelifeofthestructure.靜荷載定義attachments附屬物3.4.1DeadLoadDeadloadsareusuallyknownaccuratelybutnotuntilthedesignhasbeencompleted.Understeps3through6ofthedesignprocedure,theweightofthestructureorstructuralelementmustbeestimated,preliminarysectionselected,weightrecomputed,andmemberselectionrevisedifnecessary.Thedeadloadofattachmentsisusuallyknownwithreasonableaccuracypriortothedesign.靜荷載的確定過程revise修改；priorto在……之前3.4.1DeadLoadGravityloadsactingwhenthestructureisinservice,butvaryinginmagnitudeandlocation,aretermedliveloads.Examplesofliveloadsarehumanoccupants,furniture,movable

equipment,vehicles,andstoredgoods.Someliveloadsmaybepracticallypermanent,othersmaybehighlytransient.Becauseoftheunknownnatureofthemagnitude,location,anddensityofliveloaditems,realisticmagnitudesandthepositionsofsuchloadsareverydifficulttodetermine.活荷載的定義magnitude大小；termed被稱為；occupants居住者；movableequipment移動(dòng)設(shè)備；permanent永久的；transient短暫的3.4.2LiveLoadBecauseofthepublicconcernforadequatesafety,liveloadstobetakenasserviceloadsindesignareusuallyprescribedbystateandlocalbuildingcodes.Theseloadsaregenerallyempiricalandconservative,basedonexperienceandacceptedpracticeratherthanaccuratelycomputedvalues.Whereverlocalcodesdonotapply,ordonotexist,theprovisionsfromoneofseveralregionalandnationalbuildingcodesmaybeused.OnesuchwidelyrecognizedcodeistheAmericannationalStandardMinimumDesignLoadsforBuildingsandOtherStructuresANSIA58.1oftheAmericanNationalStandardsInstitute(ANSI),fromwhichsometypicalliveloadsarepresented.ThecodewillhenceforthbereferredtoastheANSIStandard.Thisstandardisupdatedfromtimetotime,mostrecentlyin1982.活荷載的確定方法adequate足夠的；serviceloads使用荷載；empirical憑經(jīng)驗(yàn)的；conservative保守的；provision規(guī)范；regional區(qū)域的；henceforth今后3.4.2LiveLoadLiveloadwhenappliedtoastructureshouldbepositionedtogivethemaximumeffect,includingpartialloading,alternatespanloading,orfullspanloadingasmaybenecessary.Thesimplifiedassumptionoffulluniformloadingeverywhereshouldbeusedonlywhenitagreeswithrealityorisanappropriateapproximation.Theprobabilityofhavingtheprescribedloadingapplieduniformlyoveranentirefloor,oroverallfloorsofabuildingsimultaneously,isalmostnonexistent.Mostcodesrecognizethisbyallowingforsomepercentagereductionfromfullloading.Forinstance,forliveloadsof100psformoreANSIStandardallowsmembershavinganinfluenceareaof400ft2ormoretobedesignedforareducedliveloadaccordingtoEq.3-1，asfollows:確定取得最大效應(yīng)的活荷載分布partialloading局部荷載；alternatespanloading交替跨荷載；fullspanloading全跨荷載；fulluniformloading均布荷載；appropriate適當(dāng)?shù)?；simultaneously同時(shí)3.4.2LiveLoadHighwayvehicleloadingintheUnitedStateshasbeenstandardizedbytheAmericanAssociationofStateHighwayandTransportationOfficials(AASHTO)intostandardtruckloadsandlaneloadsthatapproximateaseriesoftrucks.Therearetwosystems,designatedHandHS,thatareidentifiedbythenumberofaxlespertruck.TheHsystemhastwoaxles,whereastheHSsystemhasthreeaxlespertruck.Thereareseveralclassesofloading;however,theusualonesareknownasH20andHS20,showninFig.3-1.高速公路活荷載的分類laneloads車道荷載；designated指定的；axle車軸3.4.3HighwayLiveLoadsIndesigningagivenbridge,eitheronetruckloadingisappliedtotheentirestructure,orthelaneloadingisapplied.Whenthelaneloadingisused,theuniformportionisdistributedoverasmuchofthespanorspansaswillcausethemaximumeffect.Inaddition,theoneconcentratedload(formaximumnegativemomentoncontinuousspans,asecondconcentratedloadisalsoused)ispositionedforthemostsevereloadingeffect.Theloaddistributionacrossthewidthofabridgetoitsvarioussupportingmembersistakeninaccordancewithsemiempiricalrulesthatdependonthetypeofbridgedeckandsupportingstructure.作用于橋梁上的車輛荷載如何考慮load

distribution荷載分布；inaccordancewith符合；semiempirical半經(jīng)驗(yàn)的；bridgedeck橋面板3.4.3HighwayLiveLoadsThesingletruckloadingprovidestheeffectofaheavyconcentratedloadandusuallygovernsonrelativelyshortspans.Theuniformlaneloadistosimulatealineoftraffic,andtheaddedconcentratedloadistoaccountforthepossibilityofoneextraheavyvehicleinthelineoftraffic.Theseloadshavebeenusedwithnoapparentdifficultysince1944,beforewhichtimealineoftruckswasactuallyusedfortheloading.Ontheinterstatesystemofhighways,amilitaryloadingisalsousedthatconsistsoftwo24kip(107kN)axleloadsspaced4ft(1.2m)apart.均布車道荷載模擬一列車輛荷載governs控制；simulate模擬；interstatesystemofhighways州際高速公路系統(tǒng)3.4.3HighwayLiveLoadsThetermimpactasordinarilyusedinstructuraldesignreferstothedynamiceffectofasuddenlyappliedload.Inthebuildingofastructure,thematerialsareaddedslowly;peopleenteringabuildingarealsoconsideredagradualloading.Deadloadsarestaticloads;i.e.,theyhavenoeffectotherthanweight.Liveloadsmaybeeitherstaticortheymayhaveadynamiceffect.Personsandfurniturewouldbetreatedasstaticliveload,butcranesandvarioustypesofmachineryalsohavedynamiceffects.沖擊荷載的定義term術(shù)語；crane起重機(jī)3.4.4ImpactConsiderthespring-masssystemofFig.3-2a,wherethespringmaybethoughtofasanalogoustoanelasticbeam.Whenloadisgraduallyapplied(i.e.,staticloading)themass(weight)deflectsanamountxandtheloadonthespring(beam)isequaltotheweightW.InFig.3-2btheloadissuddenlyapplied(dynamicloading),andthemaximumdeflectionis2x;i.e.,themaximumloadonthespring(beam)is2W.Inthiscasethemassvibratesinsimpleharmonicmotionwithitsneutralpositionequaltoitsstaticdeflectedposition.Inrealstructures,theharmonic(vibratory)motionisdampedout(reducedtozero)veryrapidly.Oncethemotionhasstopped,theforceremaininginthespringistheweightW.Toaccountfortheincreasedforceduringthetimethememberisinmotion,aloadequaltotwicethestaticloadWshouldbeused—add100%ofthestaticloadtorepresentthedynamiceffect.Thisiscalleda100%impactfactor.考慮沖擊效應(yīng)的影響——沖擊因子analogous相似的；deflect偏離；vibrate振動(dòng)；simpleharmonicmotion簡(jiǎn)諧運(yùn)動(dòng)；neutralposition中性位置；dampedout衰減的；neutralposition平衡位置3.4.4ImpactAnyliveloadthatcanhaveadynamiceffectshouldbeincreasedbyanimpactfactor.Whileadynamicanalysisofastructurecouldbemade,suchaprocedureisunnecessaryinordinarydesign.Thusempirical

formulasandimpactfactorsareusuallyused.Incaseswherethedynamiceffectissmall(saywhereimpactwouldbelessthanabout20%),itisordinarilyaccountedforbyusingaconservative(higher)valueforthespecifiedliveload.Thedynamiceffectsofpersonsinbuildingsandofslow-movingvehiclesinparkinggaragesareexampleswhereordinarydesignliveloadisconservative,andusuallynoexplicitimpactfactorisadded.沖擊系數(shù)取值empiricalformulas經(jīng)驗(yàn)公式；conservative保守的；explicit明確的3.4.4ImpactInEq.3-2,L(expressedinfeet)isthelengthoftheportionofthespanthatisloadedtogivethemaximumeffectonthemember.Sincevehiclestraveldirectlyonthesuperstructure,allpartsofitaresubjectedtovibrationandmustbedesignedtoincludeimpact.Thesubstructure,includingallportionsnotrigidlyattachedtothesuperstructuresuchasabutments,retainingwalls,andpiers,areassumedtohaveadequatedampingorbesufficientlyremotefromtheapplicationpointofthedynamicloadsothatimpactmightnotbeconsidered.Again,conservativestaticloadsmayaccountforthesmallerdynamiceffects.需要考慮沖擊效應(yīng)的結(jié)構(gòu)部件portion部分；superstructure上部結(jié)構(gòu)；vibration振動(dòng)；substructure附屬結(jié)構(gòu)；abutments橋臺(tái)；retainingwalls擋土墻；pier橋墩；damping阻尼3.4.4ImpactTheliveloadingforwhichroofsaredesignediseithertotallyorprimarilyasnowload.Sincesnowhasavariablespecificgravity,evenifoneknowsthedepthofsnowforwhichdesignistobemade,theloadperunitareaofroofisatbestonlyaguess.由于雪的比重不確定，雪荷載難以直接確定3.4.5SnowLoadThebestprocedureforestablishingsnowloadfordesignistofollowtheANSIStandard.ThisCodeusesamapoftheUnitedStatesgivingisolinesofgroundsnowcorrespondingtoa50-yearmeanrecurrence

intervalforuseindesigningmostpermanentstructures.Thegroundsnowisthenmultipliedbyacoefficientthatincludestheeffectofroofslope,windexposure,nonuniformaccumulationonpitchedorcurvedroofs,multipleseriesroofs,andmultilevelroofsandroofareasadjacenttoprojectionsonarooflevel.考慮雪荷載的方式isolines等值線；correspondingto相當(dāng)于；recurrence重現(xiàn)；interval間隔；multiply乘以；coefficient系數(shù)；exposure暴露；pitched有坡度的；curved曲面的；nonuniformaccumulation不均勻堆積3.4.5SnowLoadItisapparentthatthesteepertheroofisthelesssnowcanaccumulate.Also,partialsnowloadingmustbeconsideredinadditiontofullloading,ifitisbelievedsuchloadingcanoccurandwouldcausemaximumeffects.Windmayalsoactonastructurethatiscarryingsnowload.Itisunlikely,however,thatmaximumsnowandwindloadswouldactsimultaneously.考慮雪荷載需要考慮的因素——部分堆積雪荷載、屋面坡度、風(fēng)荷載steeper傾斜的；accumulate堆積；simultaneously同時(shí)3.4.5SnowLoadIngeneral,thebasicsnowloadusedindesignvariesfrom30to40psf(1400to1900MPa)inthenorthernandeasternstatesto20psf(960MPa)orlessinthesouthernstates.Flatroofsinnormallywarmclimatesshouldbedesignedfor20psf(960MPa)evenwhensuchaccumulationofsnowmayseemdoubtful.Thisloadingmaybethoughtofasduetopeoplegatheredonsucharoof.Furthermore,thoughwindisfrequentlyignoredasaverticalforceonaroof,neverthelessitmaycausesuchaneffect.Forthesereasons,a20psf(960MPa)minimumloading,eventhoughitmaynotalwaysbesnow,isreasonable.Localcodes,actualweatherconditions,ANSI,ortheCanadianStructuralDesignManual,shouldbeusedwhendesigningforsnow.規(guī)范中規(guī)定的雪荷載值flatroof平屋面；nevertheless然而3.4.5SnowLoadAllstructuresaresubjecttowindload,butitisusuallyonlythosemorethanthreeorfourstorieshigh,otherthanlongbridges,forwhichspecialconsiderationofwindisrequired.需要考慮風(fēng)荷載的結(jié)構(gòu)otherthan除了3.4.6WindLoadOnanytypicalbuildingofrectangularplanandelevation,windexertspressureonthewindwardsideandsuctionontheleewardside,aswellaseitherupliftordownwardpressureontheroof.Formostordinarysituations,verticalroofloadingfromwindisneglectedontheassumptionthatsnowloadingwillrequireagreaterstrengththanwindloading.Thisassumptionisnottrueforsouthernclimateswheretheverticalloadingduetowindmustbeincluded.Furthermore,thetotallateralwindload,windwardandleewardeffect,iscommonlyassumedtobeappliedtothewindwardfaceofthebuilding.如何考慮風(fēng)荷載plan平面；elevation高度；windwardside迎風(fēng)面；suction吸力；leewardside背風(fēng)面；uplift向上的；lateral側(cè)面的3.4.6WindLoadThecommonlyusedwindpressureof20psf,asspecifiedbymanybuildingcodes,correspondstoavelocityof88milesperhour(mph)fromEq.3-4.AnexposurefactorCeof1.0,agustfactorCgof2.0,andashapefactor

Cpof1.3foranairtightbuilding,alongwitha20psfequivalentstaticpressurep,willgivefromEq.3-5adynamicpressureqof7.7psf,whichcorrespondsusingEq.3-4,toawindvelocityof55mph.Forallbuildingshavingnonplanarsurfaces,planesurfacesinclinedtothewinddirection,orsurfaceshavingsignificantopenings,specialdeterminationofthewindforcesshouldbemadeusingsuchsourcesastheANSIStandard,ortheNationalBuildingCodeofCanada.Formoreextensivetreatmentofwindloads,thereaderisreferredtotheTaskCommitteeonWindForces.規(guī)范中風(fēng)荷載取值specify規(guī)定；velocity速度；exposurefactor風(fēng)壓高度變化系數(shù)；gustfactor風(fēng)振系數(shù)；shapefactor風(fēng)荷載體型系數(shù)；airtight封閉的；nonplanar非平面的；inclined傾斜的；extensivetreatment眾多的處理方法；3.4.6WindLoadAnearthquakeconsistsofhorizontalandverticalgroundmotions,withtheverticalmotionusuallyhavingmuchthesmallermagnitude.Becausethehorizontalmotionofthegroundcausesthemostsignificanteffect,itisthateffectwhichisusuallythoughtofasearthquakeload.Whenthegroundunderanobject(structure)havingacertainmasssuddenlymoves,theinertiaofthemasstendstoresistthemovement,asshowninFig.3-4.Ashearforceisdevelopedbetweenthegroundandthemass.MostbuildingcodeshavingearthquakeprovisionsrequirethedesignertoconsideralateralforceCWthatisusuallyempiricallyprescribed.Thedynamicsofearthquakeactiononstructuresisoutsidethescopeofthistext,andthereaderisreferredtoChopra,CloughandPenzien.地震作用概述inertia慣性；provision規(guī)定；lateralforce橫向力；empirically以經(jīng)驗(yàn)為主的3.4.7EarthquakeLoadInordertosimplifythedesignprocess,mostbuildingcodescontainanequivalentlateralforceprocedurefordesigningtoresistearthquakes.OneofthemostwidelyuseddesignrecommendationsisthatofStructuralEngineersAssociationofCalifornia(SEAOC),thelatestversionofwhichis1974.Sincethattime,theAppliedTechnologyCouncil(ATC)preparedasetofdesignprovisions.SomerecentrulesfortheequivalentlateralforceprocedurearethosegivenbytheANSIStandard.InANSIthelateralseismicforceV,expressedasfollows,areassumedtoactnonconcurrentlyinthedirectionofeachofthemainaxesofthestructure.等效側(cè)向力方法recommendation建議；nonconcurrently不作用于同一點(diǎn)的3.4.7EarthquakeLoadThefunctionofastructureistheprincipalfactordeterminingthestructuralconfiguration.Usingthestructuralconfigurationalongwiththedesignloads,individualcomponentsareselectedtoproperlysupportandtransmitloadsthroughoutthestructure.SteelmembersareselectedfromamongthestandardrolledshapesadoptedbytheAmericanInstituteofSteelConstruction(AISC)(alsogivenbyAmericanSocietyforTestingandMaterials[ASTM]A6Specification).Ofcourse,weldingpermitscombiningplatesand/orotherrolledshapestoobtainanyshapethedesignermayrequire.鋼構(gòu)件的種類——軋制型鋼和焊接鋼構(gòu)件principal主要的；configuration布置；rolledshapes軋制型鋼；adoptedby采用；Specification規(guī)格3.5TypesofStructuralSteelMembersTypicalrolledshapes,thedimensionsforwhicharefoundintheAISCManual,areshowninFig.3-5.Themostcommonlyusedsectionisthewide-flangeshape(Fig.3-5a)whichisformedbyhotrollinginthesteelmill.Thewide-flangeshapeisdesignatedbythenominaldepthandtheweightperfoot,suchasaW18×97whichisnominally18in.deep(actualdepth=18.59in.accordingtoAISCManual)andweighs97poundsperfoot.(InSIunitstheW18×97sectioncouldbedesignatedW460×142,meaningnominally460mmdeepandhavingamassof142kg/m.)TwosetsofdimensionsarefoundintheAISCManual,onesetstatedindecimalsforthedesignertouseincomputations,andanothersetexpressedinfractions(1/16in.asthesmallestincrement)forthedetailertouseonplansandshopdrawings.RolledWshapesarealsodesignatedbyANSI/ASTMA6inaccordancewithwebthicknessasGroupsIthroughV,withthethinnestwebsectionsinGroup1.規(guī)范中軋制型鋼命名方式wide-flangeshape寬翼緣型鋼（H型鋼）；steelmill鋼鐵廠；designated命名為；decimal小數(shù)；fraction分?jǐn)?shù)；detailer放樣員；inaccordancewith按照3.5TypesofStructuralSteelMembersTheAmericanStandardbeam(Fig.3-5b),commonlycalledtheI-beam,hasrelativelynarrowandslopingflangesandathickwebcomparedtothewide-flangeshape.UseofmostI-beamshasbecomerelativelyuncommonbecauseofexcessivematerialinthewebandrelativelackoflateralstiffnessduetothenarrowflanges.I型鋼sloping傾斜的；excessive過多的3.5TypesofStructuralSteelMembersThechannel(Fig.3-5c)andangle(Fig.3-5d)arecommonlyusedeitheraloneorincombinationwithothersections.Thechannelisdesignated,forexample,asC12×20.7,anominal12in.deepchannelhavingaweightof20.7poundsperfoot.Anglesaredesignatedbytheirleglength(longlegfirst)andthickness,suchas,L6×4×3/8.槽鋼和角鋼命名方式介紹channel槽鋼；angle角鋼3.5TypesofStructuralSteelMembersThestructuraltee(Fig.3-5e)ismadebycuttingwide-flangeorI-beamsinhalfandiscommonlyusedforchordmembersintrusses.Theteeisdesignated,forexample,asWT5×44,wherethe5isthenominaldepthand44istheweightinpoundsperfoot;thisteebeingcutfromaW10×88.T型鋼structuralteeT型鋼；chordmember弦桿3.5TypesofStructuralSteelMembersThetensionmemberoccurscommonlyasachordmemberinatruss,asdiagonal

bracinginmanytypesofstructures,asdirectsupportforbalconies,ascablesinsuspendedroofsystems,andassuspensionbridgemaincablesandsuspendersthatsupporttheroadway.Typicalcross-sectionsoftensionmembersareshowninFig.3-7.受拉鋼構(gòu)件介紹diagonalbracing斜撐；balcony陽臺(tái)；cable拉索；suspensionbridge懸索橋；suspender吊桿；roadway路面；cross-section橫截面3.5.1TensionMembersSincecompressionmemberstrengthisafunctionofthecross-sectionalshape(radiusofgyration),theareaisgenerallyspreadoutasmuchasispractical.Chordmembersintrusses,andmanyinteriorcolumnsinbuildingsareexamplesofmemberssubjecttoaxialcompression.Evenunderthemostidealcondition,pureaxialcompressionisnotattainable;so,designfor“axial”loadingassumestheeffectofanysmallsimultaneousbendingmaybeneglected.Typicalcross-sectionsofcompressionmembersareshowninFig.3-8.受壓構(gòu)件radiusofgyration回轉(zhuǎn)半徑；interiorcolumns內(nèi)柱；simultaneous同時(shí)存在的3.5.2CompressionMembersBeamsarememberssubjectedtotransverseloadingandaremostefficientwhentheirareaisdistributedsoastobelocatedatthegreatestpracticaldistancefromtheneutralaxis.Themostcommonbeamsectionsarethewide-flange(W)andI-beams(S)(Fig.3-8a),aswellassmallerrolledI-shapedsectionsdesignatedas"miscellaneousshapes''(M).鋼梁用于承受橫向荷載以及常用截面形式transverseloading橫向荷載；distribute布置；miscellaneousshapes混合型鋼3.5.3BeamsWhensimultaneousactionoftensionorcompressionalongwithbendingoccurs,acombinedstressproblemarisesandthetypeofmemberusedwillbedependentonthetypeofstressthatpredominates.同時(shí)承受壓（拉）和彎矩的構(gòu)件simultaneousaction同時(shí)作用；combinedstress復(fù)合應(yīng)力；p