土木工程专业英语上册-翻译苏小卒同济考试手机专业版

Unit1第一单Fundamentally,engineeringisanend-product-orienteddisciplinethatisinnovative,cost-consciousandmindfulofhumanfactors.Itisconcernedwiththecreationofnewentities,devicesormethodsofsolution:anewprocess,anewmaterial,animprovedpowersource,amoreefficientarrangementoftaskstoplishadesiredgoaloranewstructure.Engineeringisalsomoreoftenthannotconcernedwithobtainingeconomicalsolutions.And,finally,humansafetyisalwaysakey从根本上，工程是一个以最终产品为导向的行业，它具有创新、成本意识，同时也注意到人为因素。它与创建新的实体、设备或解决方案有关：新工艺、新材料、一个改进的动力来源、任务的一项更有效地安排，用以完成所需的目标或创建一个新的结构。工程Engineeringisconcernedwiththeuseof scientificwaysofthinkingandofdefiningrealworldproblems.Theuseofidealizationsanddevelopmentofproceduresforestablishingboundswithinwhichbehaviorcanbeascertainedarepartoftheprocess.Manyproblems,bytheirverynature,can’tbefullydescribed—evenafterthefact,muchlessattheoutset.Yetacceptableengineeringsolutionstotheseproblemsmustbefoundwhichsatisfythedefinedneeds.Engineering,then,frequentlyconcernsthedeterminationofpossiblesolutionswithinacontextoflimiteddata.Intuitionorjudgmentisakeyfactorinestablishingpossiblealternativestrategies,processes,orsolutions.Andthis,too,isallapartofengineering.问题可接受的工程解决方案，来满足预定的需求。或判断是建立可能的替代策略、流程或解决方案的关键因素。。而这也是工程的一部分。Civilengineeringisoneofthemostdiversebranchesofengineering.Thecivilengineerplans,designs,constructs,andmaintainsalargevarietyofstructuresandfacilitiesforpublic,commercialandindustrialuse.Thesestructuresincluderesidential,office,andfactorybuildings;highways,,airports,tunnels,bridges,harbors,channels,andpipelines.Theyalsoincludemanyotherfacilitiesthatareapartofthetransportationsystemsofmostcountries,aswellassewageandwastedisposalsystemsthataddtoourconvenienceandsafeguardourhealth.土木工程是工程的最多样化的分支机构之Theterm“civilengineer”didnotcomeintouseuntilabout1750,whenJohnSmeaton,thebuilderoffamousEddystonelighthousenearPlymouth,England,issaidtohavebeguncallinghimselfa“civilengineer”todistinguishhimselffromthemilitaryengineersofhistime.However,theprofessionisasoldascivilization.InancientEgyptthesimplestmechanicalprinciplesanddeviceswereusedtoconstructmanytemplesandpyramidsthatarestillstanding,includingthegreatpyramidatGizaandthetempleofAmon-RaatKarnak.Thegreatpyramid,481feet(146.6meters)high,ismadeof2.25millionstoneblockshavinganaverageweightofmorethan1.5tons(1.4metrictons).Greatnumbersofmenwereusedintheconstructionofsuchmonuments.TheEgyptiansalsomadeobelisksbycuttinghugeblocksofstone,someweighingasmuchas1000tons(900metrictons).Cuttingtoolsofhardbronzewereused.古埃及人用最简单的机械原理和装置建造了许多至今仍矗立的庙宇和金字塔，包括吉萨大金字塔和在卡Amon-Ra个大金字塔，481（146.6）高，由个石块组成，石块的平均重量超1.5（1.4吨。建造如此的纪念性建筑使用了大量的人力。埃及人也作了一些重达1000900)的石头的大块切割的方尖塔。硬青铜的切削刀具在其中使用到了。TheEgyptiansbuiltcausewaysandroadsfortransportingstonefromthequarriestotheNile.ThelargeblocksofstonethatwereerectedbytheEgyptiansweremovedbyusinglevers,inclinedplanes,rollers,and TheEgyptianswereprimarilyinterestedintheknow-howofconstruction;Theyhadverylittleinterestinwhy-forofuse.Incontrast,theGreeksmadegreatstridesinintroducingtheoryintoengineeringproblemsduringthe6thto3rdcenturiesB.C.Theydevelopedan knowledgeoflines,angles,surfaces,andsolidsratherthanreferringtospecificobjects.ThegeometricbaseforGreekbuildingconstructionincludedfiguressuchasthesquare,rectangle,andtriangle.埃及人主要对如何建造感；他们对为什么这么使用没有什么太多的。相反，在公元前六世纪到公元前三世纪希腊人取得了巨大的进步于工程理论的推广。他们发展了线、角度、面，和实体的抽象的知识，而不是与特定的对象产生联系。希腊建筑施工的几TheGreekarchitektonwasusuallythedesigner,aswellasthebuilder,ofarchitecturalandengineeringmasterpieces.Hewasanarchitectandengineer.Craftsmen,masons,andsculptorsworkedunderhissupervision.IntheclassicalperiodofGreeceallimportantbuildingswerebuiltoflimestoneormarble;theParthenon,forexample,wasbuiltofmarble.希腊建筑师通常是建筑工程杰作的设计师同时也是。他既是一个建筑师也是工程师。工匠、石匠和雕塑家在他的监督下工作。Unit2二单土木工程是涉及自然资源的开发、区域性和局部地区的供水、排洪设施、废物处理设施、以及人们所需要的其他结构物的规划、设计和施工的一个工程领域。具备学历、经验又有国家关于土木工程专业实践要求认证的人员被称为土木工程师土木工程师职业标准作为专业人员，土木工程师在履行他们职责的同时，应当遵循以下的的。（即在为子孙后代保护自然资源基础的同时满足当前的需要和工程目标称为每一位雇主货委托人的忠实货委托人，并且要避免利益保持学习，总是自愿地参与理念于技术信息方面的专业交流只能在能力范围内履行职责；其他范围内，工程师可以与有资格的同事、顾问，或者雇员一起合作来执行任务。因此，土木工程的工程项目应当被规划、设计和施工以满足下列标准进行评定的时机。工程费用不应当超过业主的施工预算，并且当完全投入使用后，其运营、和工程的设计和施工要满足相关法律要求，符合公认的工程标准，同时，要避免建筑工人、工程操作者以及公众的健康和安全。应当将工程设计成满足可持续发展的要求，即在为子孙后代保藏和保护周围环境质量及自然资源的基础上满足当前工程项目的需要。 这程常常。咨询工程师一个咨询工程师被定义为一个熟练运用科原理来解决工程难题的专业。作为专业人，咨询工程应该他们的顾一样对公负责。了提专业服务，询程师也经商业易。询工程一些资企，合伙司，有建议和咨询计划规用发。设计主人。Unit3TheGreeksandRomanssometimesusedironrodsorclampstostrengthentheirbuildingThecolumnsoftheParthenoninAthens（雅典的帕台农神庙）,forexample,haveholesdrilled（钻孔）inthemforironbarsthathavenowrustedaway（锈蚀殆尽）TheRomansalsousedanaturalcementcalledpozzolanamadefromvolcanicash,thatbecameashardasstoneunderwater.其他一些粘合剂粘合在一起。希腊人和罗马人有时用铁条或来加固他们的房屋。例如，雅典的帕台农神庙柱子中曾钻孔以便加入Bothsteelandcement,thetwomostimportantconstructionmaterialsofmoderntimes,wereintroduced（推广）inthenineteenthcenturySteel,basicallyanalloyofiron（铁合金）andasmallamountofcarbon,hadbeenmadeuptothattime（到那个时候）byalaborious（繁复的）processthatrestrictedittosuchspecialusesasswordblades（刀刃）.AftertheinventionoftheBessemerprocess（贝塞麦炼钢法）in1856,steelwasavailableinlargetiesatlowprices.Theenormousadvantageofsteelisitstensilestrengththatisitdoesnotloseitsstrengthwhenitisunderacalculateddegree适当的oftension,aforcewhich,aswehaveseentendsto（往往）pullapartmanymaterialsNewalloyshavefurtherincreasedthestrengthofsteelandeliminatedsomeofitsproblemssuchasfatigue,whichisatendencyforittoweakenasaresultofcontinualchangesinstress（连续的应力变化）.1856Moderncement,calledPortlandcement,wasinventedin1824.Itisamixtureoflimestone（石灰石）andclaywhichheatedandthengroundintoapowder（磨成粉末）.Itismixedatorneartheconstructionsite（施工现场）withsand,aggregatesmallstonescrushedrock,orgravelandwatertomakeconcreteDifferentproportionsoftheingredients（配料）produceconcretewithdifferentstrengthandweightConcreteisveryversatileitcanbepoured,pumpedorevensprayedinto（喷射成）allkindsofshapes.Andwhereassteelhasgreattensilestrength,concretehasgreatstrengthundercompression.Thus,thetwosubstancescomplementeachother（互补）.Theyalsocomplementeachotherinanotherway:theyhavealmostthesamerateofcontractionandexpansionTheythereforecanworktogetherinsituationswhere（在…情况下）bothcompressionandtensionarefactors（主要因素）.Steel（钢筋）areembeddedin（埋入）concretetomakereinforcedconcreteinconcretebeamsorstructureswheretensionwilldevelop（出现）.Concreteandsteelalsoformsuchastrongbondtheforcethatunites（粘合）themthatthesteelcannotslip（滑移）withtheconcrete.Still（还有）anotheradvantageisthatsteeldoesnotrustinconcrete.Acid（酸）corrodessteelwhereasconcretehasanalkalinechemicalreactiontheoppositeof它也另外互：们乎相的缩和率因，们拉压主因时共工。出拉Theadoptionofstructuralsteelandreinforcedconcretecausedmajorchangesintraditionalconstructionpractices（施工作业）Itwasnolongernecessarytousethickwallsofstoneorbrickformultistorybuildings,anditbecamemuchsimplertobuildfire-resistantfloors（防火地面）Boththesechangesservedto（有利于）reducethecostofconstruction.Italsobecamepossibletoerect（建造）buildingswithgreaterheightsandlongerspans.Sincetheweightofmodernstructuresiscarried（承受）bythesteelorconcreteframethewallsdonotsupportthebuildingTheyhaveecurtainwallswhichkeepouttheweatherandletinlightIntheearliersteelorconcreteframebuilding,thecurtainwallsweregenerallymadeofmasonry;theyhadthesolidlookofbearingwalls（承重墙）.Today,however,curtainwallsareoftenmadeoflightweightmaterialssuchasglassaluminum,orplastic,invariousAnotheradvanceinsteelconstruction（结构）isthemethodoffasteningtogether（连在一起）thebeamsFormanyyearsthestandardmethodwasriveting.Arivetisaboltwithaheadthatlookslikeabluntscrew（圆头螺丝钉）withoutthreads（螺纹）Itisheatedplacedinholesthroughthepiecesofsteel（钢构件）andasecondheadisformedattheothertogetherofpiecesofsteelbymelting（熔化）asteelmaterialbetweenthemunderhighheat.Prestressedconcreteisanimprovedformofreinforcement（加强方法）.Steelrodsarebentintotheshapestogivethemthenecessarydegreeoftensilestrength.Theyarethenusedtoprestress（对..预加应力）concreteusuallybyoneoftwodifferentmethodsThefirstistoleavechannelsinaconcretebeamthatcorrespondto（相应于）theshapesofthesteelrodsWhentherodsarerunthroughthechannels,theyarethenbondedtotheconcretebyfillingthechannelswithgroutathinmortarorbindingagentIntheother(andmorecommonmethodtheprestressedsteelrodsareplacedinthelowerpartofaform（模板）thatcorrespondstotheshapeofthefinishedstructure（成品结构）,andtheconcretedesirable（非常理想）material.预应力混凝土是加强法的改进形式。将钢筋弯成一定的形状以使它们具有必要的抗拉强度，然后用该钢筋对混凝土施加预应力，通可采用两种不同方法中的任何一种。第法是在混凝土梁中按钢筋的形状留下孔道，当钢筋穿过孔道后，通过在孔道内灌注薄砂arenas,withlargespaceunbrokenbyanyobstructingsupports（阻碍的支撑物）.Theusesforthisrelativelynewstructuralmethodareconstantlybeingdeveloped（不断地扩大）.Thecurrenttendencyistodevelop（采用）lightermaterialsaluminum,forexample,weighsmuchlessthansteelbuthasmanyofthesameproperties.Aluminumbeamshavealreadybeenusedforbridgeconstructionandfortheframeworkofafewbuildings.Lightweightconcretes,anotherexample,arenowrapidlydevelo（发展）throughouttheworld.Theyareusedfortheirthermalinsulation(绝热性Thethreetypesareillustratedbelow（举例说明如下）:a)Concretesmadewithlightweightcasting;(c)No-finesconcretes.ab（S；(cAllthreetypesareusedfortheirinsulatingproperties（绝热性）,mainlyinhousing,wheretheygivehigh（非常）comfortincoldclimatesandalowcostofcooling（降温成本）inhotclimates.Inhousing,therelativeweaknessoflightweightconcretewallsisunimportant,butitmatters（有重大关系）inroofslabs,floorslabsandbeams.Insomelocations,somelightweightaggregatescostlittlemorethan（几乎等于）thebestdense（致密）aggregatesandalargenumberof（大量）floorslabshavethereforebeenbuiltoflightweightaggregateconcretepurelyforitsweightsaving,withnothoughtof（没考虑）itsinsulationvalue.Thelightweightaggregatereducesthefloordeadload（恒载）byabout20percentresultingin（导致）considerablesavingsinthefloor（楼盖结构）steelineveryfloorandtheroofaswellasinthecolumnsteelandlessinthefoundations.OneLondoncontractor（承包商）preferstouselightweightaggregatebecauseitgiveshimthesameweightreductioninvalueofthelightweightaggregateisonlyimportantintheroofinsulation,whichisgreatlyimproved（改进）.2（的Unit4四单（施加力）.InMechanicsofEngineeringMaterialsthemembershaveshapesthateitherexistinactualstructuresorarebeingconsideredfortheirsuitability（根据其需要）aspartsofproposed（拟建的）engineeringstructuresThematerialsinthemembershavepropertiesthatarecharacteristicofcommonlyused（常用的）engineeringmaterialssuchassteel,aluminum,concrete,andwood.Asyoucanseealreadyfromthevarietyofmaterials,forcesandshapesmentioned,MechanicsofEngineeringMaterialsisofinterestto（对..有价值）allfieldsofengineering.TheengineerusestheprinciplesofMechanicsofMaterialstodetermineifthematerialpropertiesandthedimensionsofamemberareadequateto（足以）ensurethatitcancarryitsloadssafelyandwithoutexcessivedistortion.Ingeneral（通常）,thenweareinterestedinboththesafeloadthatamembercancarryandtheassociated（相关的）deformation.Engineeringdesignwouldbeasimpleprocessifthedesignercouldtakeintoconsideration（考虑）theloadsandthemechanicalpropertiesofthematerials,manipulate（利用）anequation,andarriveat（得到）suitabledimensions.Designisseldomthatsimple.Usually（通常）onthebasisof（根据）experience,thedesignerselectsatrial（试算）memberandthendoesanysistoseeifthatmembermeetsthespecifiedrequirements.Frequently（常常）,itdoesnotsolutionisobtainedThenumberofcycles（循环次数）requiredtofindanacceptabledesigndiminishesasthedesignergainsexperience.DesignofAxiallyLoadedMembers向力构件的设Togiveyousomeinsightinto（使..有一些了解）thedesigncycleanextremelysimplememberwillbedealtwithfirst.ThatmemberisaprismaticbarwithaforceP,actingalongitslongitudinalaxisinthedirection（纵轴向）suchthatittendstoelongatethebarSuchaforceisreferredtoas（称为）anaxialtensileload（轴向拉力）andwecanreadilyimagineittryingto（努力..）pullthefibersapartandtocausefailureonatransverseplane（横向平arebeingpulledapartwiththesameloadintensity（荷载强度）WiththisassumptiontheloadintensityorstressisuniformonatransverseplaneandisgivenbywhenPisin（以..为单位）bydefinition（根据定义）Pascals(Pa).的Foragivenaxialloadandgivendimensions,thestresscanbecalculatedfrom4-1)andcomparedwith（与..相比）theAsafetyfactor（安全系数）,frequentlyimposedbyalegallyestablishedcode（）,isappliedtothestrength,asdeterminedbytests,togivetheallowablestress.Th（-是通对材料试验确定的该（验）材照与所考（验）的杆相同规范制。根据规通常对验所确定的强度考虑安全系数后得到许用应力。许用应力为这里，为材料失效（失效在下文有定义）时的应力nBeforeapproving（核准）trialdimensionsthedesignermakescertain（确信）thatthedesignissafebydeterminingthattheinequality（不等式）issatisfied.TheinequalityisusuallymoreconvenientintheItmightatfirst（起先）seemthatthedesignerwouldalwaysdimension（选定..的尺寸）thecrosssection（横截面）sothatsizessoitisusuallymoreeconomicaltowastesomematerialbyselectingthenext（接近的）largerstandardsizeabovethatrequiredbytheallowablestress.Departurefrom（背离）standardsizesisjustified（合理的）incaseswherethepenalty（不利）forexcessweightisverysevere,asinaircraft（航天器）orspace-ship（宇宙飞船）design.诸航器宇飞的计证是理，为重产的利很重。DesignofBeams的设Uptothispoint（至此）wehavelookedat（考虑）thebeamproblemasaprobleminysisthatis（即）,foragivensetofloads,spanandcrosssectionwehavebeencalculatingthestressThemorecommonlyencounteredproblemistoselectastandardsection,ordesignamemberforagivenspanandloadswithoutexceedingacertainallowablestress.Undersomeconditionstheallowablestressmaybedependentuponthedimensionsandshapeofthecrosssectioninwhichcasetheselectionofthememberesmoredifficult.Forthepresent（暂时）wewilltaketheallowablestressas（似乎）itdependsonlyonthestrengthofthematerialandthesafety（）（）能依赖横截面尺寸形状这种情下的件选会变比较。暂时用许应力法似乎只取于材的强度Atrialmemberwillbeacceptable（合格）whenthestressisequalto,orlessthantheallowablestress,thatis,ifFordesignpurposesthisinequalityismoreusefulintheformIntheusualdesignprocesstheumbendingmomentistakenfrom（取自于）thebendingmomentdiagram（弯矩图）theallowablestressisdetermined(quitefrequentlyinaccordancewith（根据）therulesofsomelegallyconstitutedcode)fromstandardstrengthtestsincombinationwith（与..结合）asafetyfactorTheright-handsideof4-6isthenknown,anditremains（仍然是）toselectordesignamemberthatwillsatisfytheinequality.WhenastandardsectionistoThistakesmoretimethanisreallynecessarysincethetablesalsoprovidethevalueofI/cforeachmemberundertheheading（标题）S,thesectionmodulus（截面模量）.在通常的计过中，大的弯从弯图上得，而用力通过标强度验并虑安全数后定（往是根一些的规则（46）I和c（-SIc的值。Thatis,thesectionmodulusisdefinedas（定义为withveryhighvaluesofSwillobviouslybeunderstressed（应力不足的）andwastefulofmaterial.Thebestdesigniftherearenootherconstraints,willbethatwhichsatisfies(4-8)withtheminimumamountofmaterial.WithtabulatedvaluesofSavailableitismuchmoreconvenienttouse(4-6)intheThesmallestacceptableSdoesnotnecessarilycoincidewith（符合）themosteconomicalmember.ToselectthelightestandmosteconomicalstandardsectionthelistedvaluesofmassshouldbeexaminedtofindthelightestmemberwithanacceptableS.Theproblemesmuchmorecomplexifbuilt-up（组合）memberisbeingdesignedbecauseitscostwilldependuponthecombinedcostsofwebplateanglesandcoverplatesaswellasfabrication（装配）costssothatthelightestmemberisnotnecessarilythemosteconomical.果没有其他的限制，最好的设计将是以最少的材料满足式（4-8）。能接受的最小S是最经济的构件。为了选择最轻和最经济的标准截面，应检查列出的质量值，以找到能接受的S值下的最轻构件。如果在设计一个组合构件时，则问题变得复杂得多，因为它DeflectionsDuetoBending弯曲挠度Themainpurposeofthischapter（本节）wastodevelop（提出）theflexure（屈曲）formulas,andtoprovidesomeexperienceinapplyingthem.Staticallyindeterminate（超静定）caseswereencounteredandsomeinsight（认识）gainedasto（就..）thedifficultyandimportanceofthiscategoryofproblem.,familiarwith（熟悉）superpositionwasmoreimportantthanfindingsolutionstotheproblems（问题的答案）becausesuperpositionhasapplicationinmanyareasofstressysisandwillbeusedfrequentlyinourfuturestudies.Moment-area（弯距图面积法）wasfoundtobeaconvenientmethodforsolvingvariousproblemsItisamethodthatesquitecomplicatedandrequiresfurtherdevelopment（展开）whenmoreadvancedstructuresareencounteredAtthepresent（长半径）curvedbeamswasintroduced（引入）toillustratethepoweroftheprinciplesunderlying（构成..的基础）themoment-areamethodandsothatyouwouldappreciate（知道）thedifferencesbetweenstraightandcurvedbeams.为决同问，现距面法一很利方但遇更进结时此得常杂需进Thischapteraffordedanopportunitytoefamiliarwithsingularityfunctions（奇异函数）,andyouhaveseenthatcertainproblemscanbegreatlysimplifiedbytheiruse.Itmustbeappreciated（）thatmerelyanintroductiontothetopichasbeengiven;thereismuchmoretolearnedbythosewhohaveaspecialinterestToillustrateaseriouslimitation（缺陷）atourpresentstage,wecanexpressdistributedloads（分布荷载）thatarevariableandareintermittent,butwecannotwritealoadfunctionforconcentratedloadsIfwehadtakenthenextstepanddealtwiththeconcentratedload,wewouldhaveencounteredthesourceoftheexpression（表达式）“singularityfunction”buthavingregardfor（考虑）thescopeofthisbookwehavestoppedshortof（达不到）thatFailureTheories失效理论intestspecimens（试件）thathadalsobeensubjectedtouniaxialloadThisisthesimplestofalldesignproblemsthemethodisquiteadequate（合适的）sincethenature（性能）oftheloadsandthestressesinthetestandinthepartbeingdesignedareidenticalHowever,wesoonencountercaseswherethememberbeingdesignedisnotsosimpleandthestressesarenotuniaxial;considerforexamplethestressesinthewebofabeamorinapressurevessel（压力容器）.ortriaxial.Foratrctrehvngbxialortrixalsrsse,hwshuldehektheaetyfhedsgn?hemostoviosaywouldbetocnucttes（进行）inhchseciensresrssd（受力tofiluenhesaemlixl多轴的）mannrasinthesrctu;teallwblemltixalsressthneetemnedbytheapliaionofnaqutesaftyfactr.Howvr,hiswuldreurearopoftetsfrevrynwetofmutaialsresesthtccredindeig.Suchetsaedfiulttoprorm,andteostofpeforingthminthereqiedubeswuldberhibiv.Consqunly,wenedatoryyhihhersltsoftestadrduixalestcanbesedopedcttefalreofaprtmadeofhesmeatrilwenhestesesaremulixal.noterors）,wenedaaluether.（试件）将要组验这的验难行而以要数行验费也是的因，们要个论根可通过Toillustratetheneedforafailuretheory,letusconsideracylindricalpressurevessel.Toavoidunnecessarycomplications,wewillconsiderthatallwelds（焊缝）are100%efficientandthatthewalls（容器壁）arethinUnderinternalpressurethemainstresses（主应力）arecircumferentialandlongitudinal,anditwasimplied（认为）inanearliercasetheadequacyofthedesign.Inthisapproachwetacitly（默认）assumedthattheumstresscouldbetreatedas（看作为）auniaxialstressandthatitalonedeterminedthesafetyofthedesignThelongitudinalstresswasnotconsideredalthoughitmay,withoutourknowledge（在我们的知识之外）havehadaninfluenceonstrength.Ithappensthatourapproachinthiscaseisacceptable,but,inabiaxialstateofstress,thesecondstressisnotalwaysinconsequential（不重要）andanunderstandingoffailuretheoryisnecessaryinordertoavoidmakingsomeseriouserrors.（）Unfortunay,aswewilldiscover,nosingletheory（单一理论）willbefoundtoapplyinallcases;forexample,theoriesthataresatisfactoryforductilematerialsarenotacceptableforbrittlematerialsWewillalsofindthatoneofthebesttheoriesistoocomplexforeverydayuseandthatmostdesignersprefer（更喜欢）asimplertheorythatintroduces（产生）asmallbutsafeside（安全的Indevelo（提出）thevariousfailuretheories,wecannotavoidthree-dimensionaleffects,butwewilltreat（讨论）onlythosecasesinwhichoneofthestressesiszerothusavoidingcomplicationsthatwouldtendtoobscure（使..模糊不清）theimportantpartofthetheories.Thisisnotaseriouslimitationsinceinengineeringpractice（工程实践）mostproblemsarereducedto（简化为）thebiaxialstressstatefordesignWhenshearstresses（剪应力）occuralong（与..一起）normalstresses（正应力）,theprincipalstresses（主应力）aredetermined.Thus,forpractical（实用的）stressiszeroForeasein（为了便于..）designating（称呼）thoseprincipalstresseswewillusenumericalsubscripts在提出同的失理论，我不能免三的影响但只讨其中某个应为零情况因而免了复性，它往往使便于称呼那些主应力，我们采用数字下标：和作为非零应力，而为零。WecannotdiscussfailuretheoryuntilwehavedefinedfailureWemighttaketheobviousdefinitionthatamaterialhasfailedwhenithasbrokeninto（分为）twoormoreparts.However,ithasalreadybeenpointedoutthatinmostapplicationsamemberwouldbeunserviceable（不再适用）duetoexcessivedistortionlongbefore（早在）itactuallyruptured（断裂）.Consequently,wewillrelatefailuretoyieldingandconsiderthatamaterialhasfailedwhenitwillnolongerreturnsaythataductilematerialhasfailedwhenthematerialbeginstoyieldThenforuniaxialstressfailureoccurswhenithertensionor在我们义了失后才对其行讨。我可能会一个显的定，即当料分两部或时失。但是在多应用中经被，一个件早它实断裂前由过分的形而再适用因此，效与服联起来并认为旦荷解除而材BrittlematerialsfailbyadifferentmechanismandwillbediscussedafterthetheoriesforductilematerialshavebeenUnit5第五单buildings,bridges,towers,,anddams.Theprocess（过程）ofcreatinganyofthesestructuresrequiresplanning（规划）,ysis,design,andconstruction（施工）.Structuralysisconsistsof（包括）avarietyofmathematicalprocedures（数学程序）fordeterminingsuchtiesasthememberforcesandvariousstructuraldisplacements（位移）isoftenapartofstructuralysis.结由系相的以撑载构组。著例括筑桥、、大等建这结中任Onlytwoassumptionsaremaderegarding（关于）thematerialsusedinthestructuresofthischapter.Firstthematerialhasalinearstress-strainrelationship（线性的应力-应变关系）Secondthereisnodifferenceinthematerialbehaviorwhenstressedintensionvis-a-vis（与..相比）compression.Theframesandtrussesstudiedareplanestructuralsystemswillfailduetoanelasticinstability（弹性失稳）.Theveryimportantconsiderationregardingsuchinstabilitywillbeleftforthespecific（具体的）designcourse.Allsrucuresreasumdtoundrgoolysmlldefratiosasteyarelade.saconequnc（）essumenochaneinhepostinordiecionofaoresareutof）trutualeflctin（.Fialy,sicelnearelasicmaerilsandmalldiplaemetreasume,hepricipeofsperosiionillaplynllcaes.Thustedispaceentsorintrnalorcsthtriseromtwoiffeentfocessytemsppledoneatati）aybeaddedlgeraiall（）todterinethestrcuresresonsewhenbothsysem()areaplidsiulaneosly.Intherealsense（真正意义上）anexactysisofastructurecanneverbecarriedoutsinceestimatesalwayshaveto（作用点）fortheloadingsmustalsobeestimated.Itisimportant,therefore,thatthestructuralengineers（形成）theabilitytomodel（模拟）oridealize（使..理想化）astructuresothatheorshecanperformapracticalforceysisofthemembers.真正意义上对一个结构准确的分析是也不可能进行的，因为总是不得不估计荷载和构成结构的材料的强度。而且，Structuralmembersarejoinedtogetherinvariouswaysdependingontheintent（意图）ofthedesignerThetwotypesofjointsmostoftenspecified（规定的）arethepinconnectionandthefixedjoint（节点）Apin-connectedjointallowssomefreedomforslight（轻微）rotation,whereasthefixedjointallowsnorelativerotationbetweentheconnectedmembers.Inreality,however,allconnectionsexhibit（显现）somestiffnesstowardjointrotations,owingtofriction（摩擦）andmaterialbehaviorWhenselectingaparticularmodelforeachsupport（支座）orjointtheengineermustbeawareforthestructuraldesign.Inreality,allstructuralsupportsactuallyexert（产生）distributedsurfaceloads（面荷载）ontheircontactingmembers.Theresultants（合力）oftheseloaddistributionsareoftenidealizedastheconcentratedforces（集中力）andmoments,byexperience.Inengineeringpractice,ifit esdoubtful（不明确）astohowtomodelastructureortransferthesothatitcanresist（抵抗）theloadingsinalltheidealizedItmayberecalled（回想）fromstaticsthatastructureoroneofitsmembersisinequilibrium（处于平衡）whenitmaintainsabalanceofforceandmomentWhenalltheforcesinastructurecanbedeterminedstrictlyfromtheseequationsthestructureisreferredtoasstaticallydeterminate（静定的）.Structureshavingmoreunknownforcesthanavailableequilibriumequations（平衡方程）arecalledstaticallyindeterminateAsageneralruleastructurecanbeidentifiedas（确定）beingeitherstaticallydeterminateorstaticallyindeterminatebydrawingfree-bodydiagrams（体图）ofallitsmembers,orselectivepartsofitsmembers,andthencomparingthetotalnumberofunknownreactiveforceandmomentcomponents（分量）withthetotalnumberofavailableequilibriumequations.过画出所构件经选择部分件的体图然后比知的反力弯矩分量总目与用的平方程数目是等来确Inparticularifastructureisstaticallyindeterminate,theadditionalequations（附加方程）neededtosolvefor（求解）theunknownreactions（反力）areobtainedbyrelatingtheappliedloadsandreactionstothedisplacementorslope（转角）atdifferentpointsonthestructureTheseequationswhicharereferredtoascompatibilityequations（相容性方程或协调方程）,mustbeequalinnumbertothedegreeofindeterminacy（不确定次数）ofthestructureCompatibilityequationsinvolve（涉及）thegeometricandphysicalpropertiesofthestructure.Therearetwofundamentalmethodsofysisfortrusses:themethodofjointsandthemethodofsections.Bothstartwith（从..着手）afree-bodydiagramofthetrussasawhole（基本上）,fromwhichtheequilibriumequationsarewrittenandsolvedforthesupportreactions（支座反力）.ThemethodofjointsAfterthesupportreactionshavebeenfoundajointisselectedthathasnomorethan（不超过）twomembersconnectingforwhichtheaxialforcesareunknownThefree-bodydiagramofthatjointisdrawn,theforcesaresummed（合计）intwodirectionsandeachsumisequatedto（等于）zeroWhendrawingthefree-bodydiagramitisagoodideatoassumethattheunknownforcesaretensionsandtoshow（表示）themsoonthefree-bodydiagrambytheirexertingapullon（对..施加拉力）thejointWhenthisisassumedtheresultingsign（符号）oftheunknownswhenitsmemberseknowns,andadjacentjoints（相邻节点）,whichmighthavehadthreeormoreunknowns,canthenbesolvedsincesomeoftheseunknownshaveeknownsThisprocess（过程）continuesfromjointtojointeachtimeselectingajointwhosenumberofunknownmembersdoesnotexceed2.节点法：出支反力后选择个节点上连着轴向知的构件超过根。画节点的体，将在两个上进行合计，每个向（）的合等于。当画出图时，好主意是定未力是拉，并在体上通对该节加一个拉构件，相的节可能曾有三或未知，但因中的一些经成已知，此也求出。个过从一个到另一个（继续）jointbyjointtowardtheotherendIfitisnecessarytoevaluatetheforcescarriedbyamemberlocated（于）somedistancefromtheendsthemethodofjointsrequiresthecalculationoftheforcesinmanymembersbeforethedesiredoneisreachedThemethodofsectionsprovidesameans（方法）foradirectcalculationinthesecasesAfterthesupportreactionshavebeencalculatedthetrussiscutthrough（切开）(ytically分析上)sothatonepartofthetrussiscompleyseveredfromtherest.Whenthisisdone,nomorethanthreeunknownmembersshouldbecut.Ifpossible（如果可能）thecut（切口）shouldpassthroughthememberormemberswhoseinternalforcesaretobefound.Afree-bodydiagramofthepartofthetrussononesideof（在..一边）thissectionisdrawn,andtheinternalforcesarefoundthroughtheequilibriumequations.Sincethesystemofforces（力系）onthefree-bodydiagramisaplanenon-concurrent（非共点）forcesystem,threeequilibriumequationsmaybewrittenandsolvedforthethreeunknowns.计算（，该出超三构的是知。果能口穿将求内的件画在面边桁部的体Influencelines（影响线）haveimportantapplicationfor（应用）thedesignofstructuresthatresistlargelive（活荷载）.Aninfluencelinerepresents（代表）thevariationofeitherthereaction,shear,momentordeflectionataspecific（特定的）pointinamemberasconcentratedforcemovesoverthemember.Oncethislineisconstructed（作图）,onecanlataglance（一眼便知）wherealiveloadshouldbeplacedonthestructuresothatitcreates（引起）thegreatestinfluenceatthespecifiedpoint.Furthermorethemagnitude（大小）oftheassociated（相关的）reaction,shearmoment,ordeflectionatthepointcanthenbecalculatedfromtheordinates（纵坐标）oftheinfluence-linediagram.Forthesereasons（因此）influencelinesplayanimportantpartinthedesignofbridgesindustrialcranerails（吊车轨道）,conveyors,andotherstructureswhereloadsmoveacrosstheirspan（全长）.Althoughtheprocedure（步骤）forconstructinganinfluencelineisratherbasic（基本的）,oneshouldclearlybeawareofthedifferencebetweenconstructin