土木工程專業(yè)英語(yǔ)上冊(cè)-翻譯蘇小卒同濟(jì)考試手機(jī)專業(yè)版

Unit1第一單Fundamentally,engineeringisanend-product-orienteddisciplinethatisinnovative,cost-consciousandmindfulofhumanfactors.Itisconcernedwiththecreationofnewentities,devicesormethodsofsolution:anewprocess,anewmaterial,animprovedpowersource,amoreefficientarrangementoftaskstoplishadesiredgoaloranewstructure.Engineeringisalsomoreoftenthannotconcernedwithobtainingeconomicalsolutions.And,finally,humansafetyisalwaysakey從根本上，工程是一個(gè)以最終產(chǎn)品為導(dǎo)向的行業(yè)，它具有創(chuàng)新、成本意識(shí)，同時(shí)也注意到人為因素。它與創(chuàng)建新的實(shí)體、設(shè)備或解決方案有關(guān)：新工藝、新材料、一個(gè)改進(jìn)的動(dòng)力來(lái)源、任務(wù)的一項(xiàng)更有效地安排，用以完成所需的目標(biāo)或創(chuàng)建一個(gè)新的結(jié)構(gòu)。工程Engineeringisconcernedwiththeuseof scientificwaysofthinkingandofdefiningrealworldproblems.Theuseofidealizationsanddevelopmentofproceduresforestablishingboundswithinwhichbehaviorcanbeascertainedarepartoftheprocess.Manyproblems,bytheirverynature,can’tbefullydescribed—evenafterthefact,muchlessattheoutset.Yetacceptableengineeringsolutionstotheseproblemsmustbefoundwhichsatisfythedefinedneeds.Engineering,then,frequentlyconcernsthedeterminationofpossiblesolutionswithinacontextoflimiteddata.Intuitionorjudgmentisakeyfactorinestablishingpossiblealternativestrategies,processes,orsolutions.Andthis,too,isallapartofengineering.問(wèn)題可接受的工程解決方案，來(lái)滿足預(yù)定的需求?；蚺袛嗍墙⒖赡艿奶娲呗?、流程或解決方案的關(guān)鍵因素。。而這也是工程的一部分。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樣化的分支機(jī)構(gòu)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.古埃及人用最簡(jiǎn)單的機(jī)械原理和裝置建造了許多至今仍矗立的廟宇和金字塔，包括吉薩大金字塔和在卡Amon-Ra個(gè)大金字塔，481（146.6）高，由個(gè)石塊組成，石塊的平均重量超1.5（1.4噸。建造如此的紀(jì)念性建筑使用了大量的人力。埃及人也作了一些重達(dá)1000900)的石頭的大塊切割的方尖塔。硬青銅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.埃及人主要對(duì)如何建造感；他們對(duì)為什么這么使用沒(méi)有什么太多的。相反，在公元前六世紀(jì)到公元前三世紀(jì)希臘人取得了巨大的進(jìn)步于工程理論的推廣。他們發(fā)展了線、角度、面，和實(shí)體的抽象的知識(shí)，而不是與特定的對(duì)象產(chǎn)生聯(lián)系。希臘建筑施工的幾TheGreekarchitektonwasusuallythedesigner,aswellasthebuilder,ofarchitecturalandengineeringmasterpieces.Hewasanarchitectandengineer.Craftsmen,masons,andsculptorsworkedunderhissupervision.IntheclassicalperiodofGreeceallimportantbuildingswerebuiltoflimestoneormarble;theParthenon,forexample,wasbuiltofmarble.希臘建筑師通常是建筑工程杰作的設(shè)計(jì)師同時(shí)也是。他既是一個(gè)建筑師也是工程師。工匠、石匠和雕塑家在他的監(jiān)督下工作。Unit2二單土木工程是涉及自然資源的開發(fā)、區(qū)域性和局部地區(qū)的供水、排洪設(shè)施、廢物處理設(shè)施、以及人們所需要的其他結(jié)構(gòu)物的規(guī)劃、設(shè)計(jì)和施工的一個(gè)工程領(lǐng)域。具備學(xué)歷、經(jīng)驗(yàn)又有國(guó)家關(guān)于土木工程專業(yè)實(shí)踐要求認(rèn)證的人員被稱為土木工程師土木工程師職業(yè)標(biāo)準(zhǔn)作為專業(yè)人員，土木工程師在履行他們職責(zé)的同時(shí)，應(yīng)當(dāng)遵循以下的的。（即在為子孫后代保護(hù)自然資源基礎(chǔ)的同時(shí)滿足當(dāng)前的需要和工程目標(biāo)稱為每一位雇主貨委托人的忠實(shí)貨委托人，并且要避免利益保持學(xué)習(xí)，總是自愿地參與理念于技術(shù)信息方面的專業(yè)交流只能在能力范圍內(nèi)履行職責(zé)；其他范圍內(nèi)，工程師可以與有資格的同事、顧問(wèn)，或者雇員一起合作來(lái)執(zhí)行任務(wù)。因此，土木工程的工程項(xiàng)目應(yīng)當(dāng)被規(guī)劃、設(shè)計(jì)和施工以滿足下列標(biāo)準(zhǔn)進(jìn)行評(píng)定的時(shí)機(jī)。工程費(fèi)用不應(yīng)當(dāng)超過(guò)業(yè)主的施工預(yù)算，并且當(dāng)完全投入使用后，其運(yùn)營(yíng)、和工程的設(shè)計(jì)和施工要滿足相關(guān)法律要求，符合公認(rèn)的工程標(biāo)準(zhǔn)，同時(shí)，要避免建筑工人、工程操作者以及公眾的健康和安全。應(yīng)當(dāng)將工程設(shè)計(jì)成滿足可持續(xù)發(fā)展的要求，即在為子孫后代保藏和保護(hù)周圍環(huán)境質(zhì)量及自然資源的基礎(chǔ)上滿足當(dāng)前工程項(xiàng)目的需要。 這程常常。咨詢工程師一個(gè)咨詢工程師被定義為一個(gè)熟練運(yùn)用科原理來(lái)解決工程難題的專業(yè)。作為專業(yè)人，咨詢工程應(yīng)該他們的顧一樣對(duì)公負(fù)責(zé)。了提專業(yè)服務(wù)，詢程師也經(jīng)商業(yè)易。詢工程一些資企，合伙司，有建議和咨詢計(jì)劃規(guī)用發(fā)。設(shè)計(jì)主人。Unit3TheGreeksandRomanssometimesusedironrodsorclampstostrengthentheirbuildingThecolumnsoftheParthenoninAthens（雅典的帕臺(tái)農(nóng)神廟）,forexample,haveholesdrilled（鉆孔）inthemforironbarsthathavenowrustedaway（銹蝕殆盡）TheRomansalsousedanaturalcementcalledpozzolanamadefromvolcanicash,thatbecameashardasstoneunderwater.其他一些粘合劑粘合在一起。希臘人和羅馬人有時(shí)用鐵條或來(lái)加固他們的房屋。例如，雅典的帕臺(tái)農(nóng)神廟柱子中曾鉆孔以便加入Bothsteelandcement,thetwomostimportantconstructionmaterialsofmoderntimes,wereintroduced（推廣）inthenineteenthcenturySteel,basicallyanalloyofiron（鐵合金）andasmallamountofcarbon,hadbeenmadeuptothattime（到那個(gè)時(shí)候）byalaborious（繁復(fù)的）processthatrestrictedittosuchspecialusesasswordblades（刀刃）.AftertheinventionoftheBessemerprocess（貝塞麥煉鋼法）in1856,steelwasavailableinlargetiesatlowprices.Theenormousadvantageofsteelisitstensilestrengththatisitdoesnotloseitsstrengthwhenitisunderacalculateddegree適當(dāng)?shù)膐ftension,aforcewhich,aswehaveseentendsto（往往）pullapartmanymaterialsNewalloyshavefurtherincreasedthestrengthofsteelandeliminatedsomeofitsproblemssuchasfatigue,whichisatendencyforittoweakenasaresultofcontinualchangesinstress（連續(xù)的應(yīng)力變化）.1856Moderncement,calledPortlandcement,wasinventedin1824.Itisamixtureoflimestone（石灰石）andclaywhichheatedandthengroundintoapowder（磨成粉末）.Itismixedatorneartheconstructionsite（施工現(xiàn)場(chǎng)）withsand,aggregatesmallstonescrushedrock,orgravelandwatertomakeconcreteDifferentproportionsoftheingredients（配料）produceconcretewithdifferentstrengthandweightConcreteisveryversatileitcanbepoured,pumpedorevensprayedinto（噴射成）allkindsofshapes.Andwhereassteelhasgreattensilestrength,concretehasgreatstrengthundercompression.Thus,thetwosubstancescomplementeachother（互補(bǔ)）.Theyalsocomplementeachotherinanotherway:theyhavealmostthesamerateofcontractionandexpansionTheythereforecanworktogetherinsituationswhere（在…情況下）bothcompressionandtensionarefactors（主要因素）.Steel（鋼筋）areembeddedin（埋入）concretetomakereinforcedconcreteinconcretebeamsorstructureswheretensionwilldevelop（出現(xiàn)）.Concreteandsteelalsoformsuchastrongbondtheforcethatunites（粘合）themthatthesteelcannotslip（滑移）withtheconcrete.Still（還有）anotheradvantageisthatsteeldoesnotrustinconcrete.Acid（酸）corrodessteelwhereasconcretehasanalkalinechemicalreactiontheoppositeof它也另外互：們乎相的縮和率因，們拉壓主因時(shí)共工。出拉Theadoptionofstructuralsteelandreinforcedconcretecausedmajorchangesintraditionalconstructionpractices（施工作業(yè)）Itwasnolongernecessarytousethickwallsofstoneorbrickformultistorybuildings,anditbecamemuchsimplertobuildfire-resistantfloors（防火地面）Boththesechangesservedto（有利于）reducethecostofconstruction.Italsobecamepossibletoerect（建造）buildingswithgreaterheightsandlongerspans.Sincetheweightofmodernstructuresiscarried（承受）bythesteelorconcreteframethewallsdonotsupportthebuildingTheyhaveecurtainwallswhichkeepouttheweatherandletinlightIntheearliersteelorconcreteframebuilding,thecurtainwallsweregenerallymadeofmasonry;theyhadthesolidlookofbearingwalls（承重墻）.Today,however,curtainwallsareoftenmadeoflightweightmaterialssuchasglassaluminum,orplastic,invariousAnotheradvanceinsteelconstruction（結(jié)構(gòu)）isthemethodoffasteningtogether（連在一起）thebeamsFormanyyearsthestandardmethodwasriveting.Arivetisaboltwithaheadthatlookslikeabluntscrew（圓頭螺絲釘）withoutthreads（螺紋）Itisheatedplacedinholesthroughthepiecesofsteel（鋼構(gòu)件）andasecondheadisformedattheothertogetherofpiecesofsteelbymelting（熔化）asteelmaterialbetweenthemunderhighheat.Prestressedconcreteisanimprovedformofreinforcement（加強(qiáng)方法）.Steelrodsarebentintotheshapestogivethemthenecessarydegreeoftensilestrength.Theyarethenusedtoprestress（對(duì)..預(yù)加應(yīng)力）concreteusuallybyoneoftwodifferentmethodsThefirstistoleavechannelsinaconcretebeamthatcorrespondto（相應(yīng)于）theshapesofthesteelrodsWhentherodsarerunthroughthechannels,theyarethenbondedtotheconcretebyfillingthechannelswithgroutathinmortarorbindingagentIntheother(andmorecommonmethodtheprestressedsteelrodsareplacedinthelowerpartofaform（模板）thatcorrespondstotheshapeofthefinishedstructure（成品結(jié)構(gòu)）,andtheconcretedesirable（非常理想）material.預(yù)應(yīng)力混凝土是加強(qiáng)法的改進(jìn)形式。將鋼筋彎成一定的形狀以使它們具有必要的抗拉強(qiáng)度，然后用該鋼筋對(duì)混凝土施加預(yù)應(yīng)力，通可采用兩種不同方法中的任何一種。第法是在混凝土梁中按鋼筋的形狀留下孔道，當(dāng)鋼筋穿過(guò)孔道后，通過(guò)在孔道內(nèi)灌注薄砂arenas,withlargespaceunbrokenbyanyobstructingsupports（阻礙的支撐物）.Theusesforthisrelativelynewstructuralmethodareconstantlybeingdeveloped（不斷地?cái)U(kuò)大）.Thecurrenttendencyistodevelop（采用）lightermaterialsaluminum,forexample,weighsmuchlessthansteelbuthasmanyofthesameproperties.Aluminumbeamshavealreadybeenusedforbridgeconstructionandfortheframeworkofafewbuildings.Lightweightconcretes,anotherexample,arenowrapidlydevelo（發(fā)展）throughouttheworld.Theyareusedfortheirthermalinsulation(絕熱性Thethreetypesareillustratedbelow（舉例說(shuō)明如下）:a)Concretesmadewithlightweightcasting;(c)No-finesconcretes.ab（S；(cAllthreetypesareusedfortheirinsulatingproperties（絕熱性）,mainlyinhousing,wheretheygivehigh（非常）comfortincoldclimatesandalowcostofcooling（降溫成本）inhotclimates.Inhousing,therelativeweaknessoflightweightconcretewallsisunimportant,butitmatters（有重大關(guān)系）inroofslabs,floorslabsandbeams.Insomelocations,somelightweightaggregatescostlittlemorethan（幾乎等于）thebestdense（致密）aggregatesandalargenumberof（大量）floorslabshavethereforebeenbuiltoflightweightaggregateconcretepurelyforitsweightsaving,withnothoughtof（沒(méi)考慮）itsinsulationvalue.Thelightweightaggregatereducesthefloordeadload（恒載）byabout20percentresultingin（導(dǎo)致）considerablesavingsinthefloor（樓蓋結(jié)構(gòu)）steelineveryfloorandtheroofaswellasinthecolumnsteelandlessinthefoundations.OneLondoncontractor（承包商）preferstouselightweightaggregatebecauseitgiveshimthesameweightreductioninvalueofthelightweightaggregateisonlyimportantintheroofinsulation,whichisgreatlyimproved（改進(jìn)）.2（的Unit4四單（施加力）.InMechanicsofEngineeringMaterialsthemembershaveshapesthateitherexistinactualstructuresorarebeingconsideredfortheirsuitability（根據(jù)其需要）aspartsofproposed（擬建的）engineeringstructuresThematerialsinthemembershavepropertiesthatarecharacteristicofcommonlyused（常用的）engineeringmaterialssuchassteel,aluminum,concrete,andwood.Asyoucanseealreadyfromthevarietyofmaterials,forcesandshapesmentioned,MechanicsofEngineeringMaterialsisofinterestto（對(duì)..有價(jià)值）allfieldsofengineering.TheengineerusestheprinciplesofMechanicsofMaterialstodetermineifthematerialpropertiesandthedimensionsofamemberareadequateto（足以）ensurethatitcancarryitsloadssafelyandwithoutexcessivedistortion.Ingeneral（通常）,thenweareinterestedinboththesafeloadthatamembercancarryandtheassociated（相關(guān)的）deformation.Engineeringdesignwouldbeasimpleprocessifthedesignercouldtakeintoconsideration（考慮）theloadsandthemechanicalpropertiesofthematerials,manipulate（利用）anequation,andarriveat（得到）suitabledimensions.Designisseldomthatsimple.Usually（通常）onthebasisof（根據(jù)）experience,thedesignerselectsatrial（試算）memberandthendoesanysistoseeifthatmembermeetsthespecifiedrequirements.Frequently（常常）,itdoesnotsolutionisobtainedThenumberofcycles（循環(huán)次數(shù)）requiredtofindanacceptabledesigndiminishesasthedesignergainsexperience.DesignofAxiallyLoadedMembers向力構(gòu)件的設(shè)Togiveyousomeinsightinto（使..有一些了解）thedesigncycleanextremelysimplememberwillbedealtwithfirst.ThatmemberisaprismaticbarwithaforceP,actingalongitslongitudinalaxisinthedirection（縱軸向）suchthatittendstoelongatethebarSuchaforceisreferredtoas（稱為）anaxialtensileload（軸向拉力）andwecanreadilyimagineittryingto（努力..）pullthefibersapartandtocausefailureonatransverseplane（橫向平arebeingpulledapartwiththesameloadintensity（荷載強(qiáng)度）WiththisassumptiontheloadintensityorstressisuniformonatransverseplaneandisgivenbywhenPisin（以..為單位）bydefinition（根據(jù)定義）Pascals(Pa).的Foragivenaxialloadandgivendimensions,thestresscanbecalculatedfrom4-1)andcomparedwith（與..相比）theAsafetyfactor（安全系數(shù)）,frequentlyimposedbyalegallyestablishedcode（）,isappliedtothestrength,asdeterminedbytests,togivetheallowablestress.Th（-是通對(duì)材料試驗(yàn)確定的該（驗(yàn)）材照與所考（驗(yàn)）的桿相同規(guī)范制。根據(jù)規(guī)通常對(duì)驗(yàn)所確定的強(qiáng)度考慮安全系數(shù)后得到許用應(yīng)力。許用應(yīng)力為這里，為材料失效（失效在下文有定義）時(shí)的應(yīng)力nBeforeapproving（核準(zhǔn)）trialdimensionsthedesignermakescertain（確信）thatthedesignissafebydeterminingthattheinequality（不等式）issatisfied.TheinequalityisusuallymoreconvenientintheItmightatfirst（起先）seemthatthedesignerwouldalwaysdimension（選定..的尺寸）thecrosssection（橫截面）sothatsizessoitisusuallymoreeconomicaltowastesomematerialbyselectingthenext（接近的）largerstandardsizeabovethatrequiredbytheallowablestress.Departurefrom（背離）standardsizesisjustified（合理的）incaseswherethepenalty（不利）forexcessweightisverysevere,asinaircraft（航天器）orspace-ship（宇宙飛船）design.諸航器宇飛的計(jì)證是理，為重產(chǎn)的利很重。DesignofBeams的設(shè)Uptothispoint（至此）wehavelookedat（考慮）thebeamproblemasaprobleminysisthatis（即）,foragivensetofloads,spanandcrosssectionwehavebeencalculatingthestressThemorecommonlyencounteredproblemistoselectastandardsection,ordesignamemberforagivenspanandloadswithoutexceedingacertainallowablestress.Undersomeconditionstheallowablestressmaybedependentuponthedimensionsandshapeofthecrosssectioninwhichcasetheselectionofthememberesmoredifficult.Forthepresent（暫時(shí)）wewilltaketheallowablestressas（似乎）itdependsonlyonthestrengthofthematerialandthesafety（）（）能依賴橫截面尺寸形狀這種情下的件選會(huì)變比較。暫時(shí)用許應(yīng)力法似乎只取于材的強(qiáng)度Atrialmemberwillbeacceptable（合格）whenthestressisequalto,orlessthantheallowablestress,thatis,ifFordesignpurposesthisinequalityismoreusefulintheformIntheusualdesignprocesstheumbendingmomentistakenfrom（取自于）thebendingmomentdiagram（彎矩圖）theallowablestressisdetermined(quitefrequentlyinaccordancewith（根據(jù)）therulesofsomelegallyconstitutedcode)fromstandardstrengthtestsincombinationwith（與..結(jié)合）asafetyfactorTheright-handsideof4-6isthenknown,anditremains（仍然是）toselectordesignamemberthatwillsatisfytheinequality.WhenastandardsectionistoThistakesmoretimethanisreallynecessarysincethetablesalsoprovidethevalueofI/cforeachmemberundertheheading（標(biāo)題）S,thesectionmodulus（截面模量）.在通常的計(jì)過(guò)中，大的彎從彎圖上得，而用力通過(guò)標(biāo)強(qiáng)度驗(yàn)并慮安全數(shù)后定（往是根一些的規(guī)則（46）I和c（-SIc的值。Thatis,thesectionmodulusisdefinedas（定義為withveryhighvaluesofSwillobviouslybeunderstressed（應(yīng)力不足的）andwastefulofmaterial.Thebestdesigniftherearenootherconstraints,willbethatwhichsatisfies(4-8)withtheminimumamountofmaterial.WithtabulatedvaluesofSavailableitismuchmoreconvenienttouse(4-6)intheThesmallestacceptableSdoesnotnecessarilycoincidewith（符合）themosteconomicalmember.ToselectthelightestandmosteconomicalstandardsectionthelistedvaluesofmassshouldbeexaminedtofindthelightestmemberwithanacceptableS.Theproblemesmuchmorecomplexifbuilt-up（組合）memberisbeingdesignedbecauseitscostwilldependuponthecombinedcostsofwebplateanglesandcoverplatesaswellasfabrication（裝配）costssothatthelightestmemberisnotnecessarilythemosteconomical.果沒(méi)有其他的限制，最好的設(shè)計(jì)將是以最少的材料滿足式（4-8）。能接受的最小S是最經(jīng)濟(jì)的構(gòu)件。為了選擇最輕和最經(jīng)濟(jì)的標(biāo)準(zhǔn)截面，應(yīng)檢查列出的質(zhì)量值，以找到能接受的S值下的最輕構(gòu)件。如果在設(shè)計(jì)一個(gè)組合構(gòu)件時(shí)，則問(wèn)題變得復(fù)雜得多，因?yàn)樗麯eflectionsDuetoBending彎曲撓度Themainpurposeofthischapter（本節(jié)）wastodevelop（提出）theflexure（屈曲）formulas,andtoprovidesomeexperienceinapplyingthem.Staticallyindeterminate（超靜定）caseswereencounteredandsomeinsight（認(rèn)識(shí)）gainedasto（就..）thedifficultyandimportanceofthiscategoryofproblem.,familiarwith（熟悉）superpositionwasmoreimportantthanfindingsolutionstotheproblems（問(wèn)題的答案）becausesuperpositionhasapplicationinmanyareasofstressysisandwillbeusedfrequentlyinourfuturestudies.Moment-area（彎距圖面積法）wasfoundtobeaconvenientmethodforsolvingvariousproblemsItisamethodthatesquitecomplicatedandrequiresfurtherdevelopment（展開）whenmoreadvancedstructuresareencounteredAtthepresent（長(zhǎng)半徑）curvedbeamswasintroduced（引入）toillustratethepoweroftheprinciplesunderlying（構(gòu)成..的基礎(chǔ)）themoment-areamethodandsothatyouwouldappreciate（知道）thedifferencesbetweenstraightandcurvedbeams.為決同問(wèn)，現(xiàn)距面法一很利方但遇更進(jìn)結(jié)時(shí)此得常雜需進(jìn)Thischapteraffordedanopportunitytoefamiliarwithsingularityfunctions（奇異函數(shù)）,andyouhaveseenthatcertainproblemscanbegreatlysimplifiedbytheiruse.Itmustbeappreciated（）thatmerelyanintroductiontothetopichasbeengiven;thereismuchmoretolearnedbythosewhohaveaspecialinterestToillustrateaseriouslimitation（缺陷）atourpresentstage,wecanexpressdistributedloads（分布荷載）thatarevariableandareintermittent,butwecannotwritealoadfunctionforconcentratedloadsIfwehadtakenthenextstepanddealtwiththeconcentratedload,wewouldhaveencounteredthesourceoftheexpression（表達(dá)式）“singularityfunction”buthavingregardfor（考慮）thescopeofthisbookwehavestoppedshortof（達(dá)不到）thatFailureTheories失效理論intestspecimens（試件）thathadalsobeensubjectedtouniaxialloadThisisthesimplestofalldesignproblemsthemethodisquiteadequate（合適的）sincethenature（性能）oftheloadsandthestressesinthetestandinthepartbeingdesignedareidenticalHowever,wesoonencountercaseswherethememberbeingdesignedisnotsosimpleandthestressesarenotuniaxial;considerforexamplethestressesinthewebofabeamorinapressurevessel（壓力容器）.ortriaxial.Foratrctrehvngbxialortrixalsrsse,hwshuldehektheaetyfhedsgn?hemostoviosaywouldbetocnucttes（進(jìn)行）inhchseciensresrssd（受力tofiluenhesaemlixl多軸的）mannrasinthesrctu;teallwblemltixalsressthneetemnedbytheapliaionofnaqutesaftyfactr.Howvr,hiswuldreurearopoftetsfrevrynwetofmutaialsresesthtccredindeig.Suchetsaedfiulttoprorm,andteostofpeforingthminthereqiedubeswuldberhibiv.Consqunly,wenedatoryyhihhersltsoftestadrduixalestcanbesedopedcttefalreofaprtmadeofhesmeatrilwenhestesesaremulixal.noterors）,wenedaaluether.（試件）將要組驗(yàn)這的驗(yàn)難行而以要數(shù)行驗(yàn)費(fèi)也是的因，們要個(gè)論根可通過(guò)Toillustratetheneedforafailuretheory,letusconsideracylindricalpressurevessel.Toavoidunnecessarycomplications,wewillconsiderthatallwelds（焊縫）are100%efficientandthatthewalls（容器壁）arethinUnderinternalpressurethemainstresses（主應(yīng)力）arecircumferentialandlongitudinal,anditwasimplied（認(rèn)為）inanearliercasetheadequacyofthedesign.Inthisapproachwetacitly（默認(rèn)）assumedthattheumstresscouldbetreatedas（看作為）auniaxialstressandthatitalonedeterminedthesafetyofthedesignThelongitudinalstresswasnotconsideredalthoughitmay,withoutourknowledge（在我們的知識(shí)之外）havehadaninfluenceonstrength.Ithappensthatourapproachinthiscaseisacceptable,but,inabiaxialstateofstress,thesecondstressisnotalwaysinconsequential（不重要）andanunderstandingoffailuretheoryisnecessaryinordertoavoidmakingsomeseriouserrors.（）Unfortunay,aswewilldiscover,nosingletheory（單一理論）willbefoundtoapplyinallcases;forexample,theoriesthataresatisfactoryforductilematerialsarenotacceptableforbrittlematerialsWewillalsofindthatoneofthebesttheoriesistoocomplexforeverydayuseandthatmostdesignersprefer（更喜歡）asimplertheorythatintroduces（產(chǎn)生）asmallbutsafeside（安全的Indevelo（提出）thevariousfailuretheories,wecannotavoidthree-dimensionaleffects,butwewilltreat（討論）onlythosecasesinwhichoneofthestressesiszerothusavoidingcomplicationsthatwouldtendtoobscure（使..模糊不清）theimportantpartofthetheories.Thisisnotaseriouslimitationsinceinengineeringpractice（工程實(shí)踐）mostproblemsarereducedto（簡(jiǎn)化為）thebiaxialstressstatefordesignWhenshearstresses（剪應(yīng)力）occuralong（與..一起）normalstresses（正應(yīng)力）,theprincipalstresses（主應(yīng)力）aredetermined.Thus,forpractical（實(shí)用的）stressiszeroForeasein（為了便于..）designating（稱呼）thoseprincipalstresseswewillusenumericalsubscripts在提出同的失理論，我不能免三的影響但只討其中某個(gè)應(yīng)為零情況因而免了復(fù)性，它往往使便于稱呼那些主應(yīng)力，我們采用數(shù)字下標(biāo)：和作為非零應(yīng)力，而為零。WecannotdiscussfailuretheoryuntilwehavedefinedfailureWemighttaketheobviousdefinitionthatamaterialhasfailedwhenithasbrokeninto（分為）twoormoreparts.However,ithasalreadybeenpointedoutthatinmostapplicationsamemberwouldbeunserviceable（不再適用）duetoexcessivedistortionlongbefore（早在）itactuallyruptured（斷裂）.Consequently,wewillrelatefailuretoyieldingandconsiderthatamaterialhasfailedwhenitwillnolongerreturnsaythataductilematerialhasfailedwhenthematerialbeginstoyieldThenforuniaxialstressfailureoccurswhenithertensionor在我們義了失后才對(duì)其行討。我可能會(huì)一個(gè)顯的定，即當(dāng)料分兩部或時(shí)失。但是在多應(yīng)用中經(jīng)被，一個(gè)件早它實(shí)斷裂前由過(guò)分的形而再適用因此，效與服聯(lián)起來(lái)并認(rèn)為旦荷解除而材BrittlematerialsfailbyadifferentmechanismandwillbediscussedafterthetheoriesforductilematerialshavebeenUnit5第五單buildings,bridges,towers,,anddams.Theprocess（過(guò)程）ofcreatinganyofthesestructuresrequiresplanning（規(guī)劃）,ysis,design,andconstruction（施工）.Structuralysisconsistsof（包括）avarietyofmathematicalprocedures（數(shù)學(xué)程序）fordeterminingsuchtiesasthememberforcesandvariousstructuraldisplacements（位移）isoftenapartofstructuralysis.結(jié)由系相的以撐載構(gòu)組。著例括筑橋、、大等建這結(jié)中任Onlytwoassumptionsaremaderegarding（關(guān)于）thematerialsusedinthestructuresofthischapter.Firstthematerialhasalinearstress-strainrelationship（線性的應(yīng)力-應(yīng)變關(guān)系）Secondthereisnodifferenceinthematerialbehaviorwhenstressedintensionvis-a-vis（與..相比）compression.Theframesandtrussesstudiedareplanestructuralsystemswillfailduetoanelasticinstability（彈性失穩(wěn)）.Theveryimportantconsiderationregardingsuchinstabilitywillbeleftforthespecific（具體的）designcourse.Allsrucuresreasumdtoundrgoolysmlldefratiosasteyarelade.saconequnc（）essumenochaneinhepostinordiecionofaoresareutof）trutualeflctin（.Fialy,sicelnearelasicmaerilsandmalldiplaemetreasume,hepricipeofsperosiionillaplynllcaes.Thustedispaceentsorintrnalorcsthtriseromtwoiffeentfocessytemsppledoneatati）aybeaddedlgeraiall（）todterinethestrcuresresonsewhenbothsysem()areaplidsiulaneosly.Intherealsense（真正意義上）anexactysisofastructurecanneverbecarriedoutsinceestimatesalwayshaveto（作用點(diǎn)）fortheloadingsmustalsobeestimated.Itisimportant,therefore,thatthestructuralengineers（形成）theabilitytomodel（模擬）oridealize（使..理想化）astructuresothatheorshecanperformapracticalforceysisofthemembers.真正意義上對(duì)一個(gè)結(jié)構(gòu)準(zhǔn)確的分析是也不可能進(jìn)行的，因?yàn)榭偸遣坏貌还烙?jì)荷載和構(gòu)成結(jié)構(gòu)的材料的強(qiáng)度。而且，Structuralmembersarejoinedtogetherinvariouswaysdependingontheintent（意圖）ofthedesignerThetwotypesofjointsmostoftenspecified（規(guī)定的）arethepinconnectionandthefixedjoint（節(jié)點(diǎn)）Apin-connectedjointallowssomefreedomforslight（輕微）rotation,whereasthefixedjointallowsnorelativerotationbetweentheconnectedmembers.Inreality,however,allconnectionsexhibit（顯現(xiàn)）somestiffnesstowardjointrotations,owingtofriction（摩擦）andmaterialbehaviorWhenselectingaparticularmodelforeachsupport（支座）orjointtheengineermustbeawareforthestructuraldesign.Inreality,allstructuralsupportsactuallyexert（產(chǎn)生）distributedsurfaceloads（面荷載）ontheircontactingmembers.Theresultants（合力）oftheseloaddistributionsareoftenidealizedastheconcentratedforces（集中力）andmoments,byexperience.Inengineeringpractice,ifit esdoubtful（不明確）astohowtomodelastructureortransferthesothatitcanresist（抵抗）theloadingsinalltheidealizedItmayberecalled（回想）fromstaticsthatastructureoroneofitsmembersisinequilibrium（處于平衡）whenitmaintainsabalanceofforceandmomentWhenalltheforcesinastructurecanbedeterminedstrictlyfromtheseequationsthestructureisreferredtoasstaticallydeterminate（靜定的）.Structureshavingmoreunknownforcesthanavailableequilibriumequations（平衡方程）arecalledstaticallyindeterminateAsageneralruleastructurecanbeidentifiedas（確定）beingeitherstaticallydeterminateorstaticallyindeterminatebydrawingfree-bodydiagrams（體圖）ofallitsmembers,orselectivepartsofitsmembers,andthencomparingthetotalnumberofunknownreactiveforceandmomentcomponents（分量）withthetotalnumberofavailableequilibriumequations.過(guò)畫出所構(gòu)件經(jīng)選擇部分件的體圖然后比知的反力彎矩分量總目與用的平方程數(shù)目是等來(lái)確Inparticularifastructureisstaticallyindeterminate,theadditionalequations（附加方程）neededtosolvefor（求解）theunknownreactions（反力）areobtainedbyrelatingtheappliedloadsandreactionstothedisplacementorslope（轉(zhuǎn)角）atdifferentpointsonthestructureTheseequationswhicharereferredtoascompatibilityequations（相容性方程或協(xié)調(diào)方程）,mustbeequalinnumbertothedegreeofindeterminacy（不確定次數(shù)）ofthestructureCompatibilityequationsinvolve（涉及）thegeometricandphysicalpropertiesofthestructure.Therearetwofundamentalmethodsofysisfortrusses:themethodofjointsandthemethodofsections.Bothstartwith（從..著手）afree-bodydiagramofthetrussasawhole（基本上）,fromwhichtheequilibriumequationsarewrittenandsolvedforthesupportreactions（支座反力）.ThemethodofjointsAfterthesupportreactionshavebeenfoundajointisselectedthathasnomorethan（不超過(guò)）twomembersconnectingforwhichtheaxialforcesareunknownThefree-bodydiagramofthatjointisdrawn,theforcesaresummed（合計(jì)）intwodirectionsandeachsumisequatedto（等于）zeroWhendrawingthefree-bodydiagramitisagoodideatoassumethattheunknownforcesaretensionsandtoshow（表示）themsoonthefree-bodydiagrambytheirexertingapullon（對(duì)..施加拉力）thejointWhenthisisassumedtheresultingsign（符號(hào)）oftheunknownswhenitsmemberseknowns,andadjacentjoints（相鄰節(jié)點(diǎn)）,whichmighthavehadthreeormoreunknowns,canthenbesolvedsincesomeoftheseunknownshaveeknownsThisprocess（過(guò)程）continuesfromjointtojointeachtimeselectingajointwhosenumberofunknownmembersdoesnotexceed2.節(jié)點(diǎn)法：出支反力后選擇個(gè)節(jié)點(diǎn)上連著軸向知的構(gòu)件超過(guò)根。畫節(jié)點(diǎn)的體，將在兩個(gè)上進(jìn)行合計(jì)，每個(gè)向（）的合等于。當(dāng)畫出圖時(shí)，好主意是定未力是拉，并在體上通對(duì)該節(jié)加一個(gè)拉構(gòu)件，相的節(jié)可能曾有三或未知，但因中的一些經(jīng)成已知，此也求出。個(gè)過(guò)從一個(gè)到另一個(gè)（繼續(xù)）jointbyjointtowardtheotherendIfitisnecessarytoevaluatetheforcescarriedbyamemberlocated（于）somedistancefromtheendsthemethodofjointsrequiresthecalculationoftheforcesinmanymembersbeforethedesiredoneisreachedThemethodofsectionsprovidesameans（方法）foradirectcalculationinthesecasesAfterthesupportreactionshavebeencalculatedthetrussiscutthrough（切開）(ytically分析上)sothatonepartofthetrussiscompleyseveredfromtherest.Whenthisisdone,nomorethanthreeunknownmembersshouldbecut.Ifpossible（如果可能）thecut（切口）shouldpassthroughthememberormemberswhoseinternalforcesaretobefound.Afree-bodydiagramofthepartofthetrussononesideof（在..一邊）thissectionisdrawn,andtheinternalforcesarefoundthroughtheequilibriumequations.Sincethesystemofforces（力系）onthefree-bodydiagramisaplanenon-concurrent（非共點(diǎn)）forcesystem,threeequilibriumequationsmaybewrittenandsolvedforthethreeunknowns.計(jì)算（，該出超三構(gòu)的是知。果能口穿將求內(nèi)的件畫在面邊桁部的體Influencelines（影響線）haveimportantapplicationfor（應(yīng)用）thedesignofstructuresthatresistlargelive（活荷載）.Aninfluencelinerepresents（代表）thevariationofeitherthereaction,shear,momentordeflectionataspecific（特定的）pointinamemberasconcentratedforcemovesoverthemember.Oncethislineisconstructed（作圖）,onecanlataglance（一眼便知）wherealiveloadshouldbeplacedonthestructuresothatitcreates（引起）thegreatestinfluenceatthespecifiedpoint.Furthermorethemagnitude（大?。﹐ftheassociated（相關(guān)的）reaction,shearmoment,ordeflectionatthepointcanthenbecalculatedfromtheordinates（縱坐標(biāo)）oftheinfluence-linediagram.Forthesereasons（因此）influencelinesplayanimportantpartinthedesignofbridgesindustrialcranerails（吊車軌道）,conveyors,andotherstructureswhereloadsmoveacrosstheirspan（全長(zhǎng)）.Althoughtheprocedure（步驟）forconstructinganinfluencelineisratherbasic（基本的）,oneshouldclearlybeawareofthedifferencebetweenconstructin