专业英语[土木工程专业(路桥方向)]

Lesson1CareersinCivilEngineeringManycivilengineers,amongthemthetoppeopleinthefieldworkindesign.Aswehaveseen,civilengineersworkonmanydiferentkindsofstructures,soitisnormalpracticeforanengineertospecializeinjustonekind.Indesigningbuildings,engineersoftenworkasconsultantstoarchitecturalorconstructionfirm.Dams,bridges,watersupplysystemsandotherlargeprojectordinarilyemployseveralengineerswhoseworkiscoordinatedbyasystemenginneerwhoisinchargeoftheentireproject.Inmanycasesengineersfromotherdisciplinesareinvolved.Indamproject,forexample,electricalandmechanicalengineersworkonthedesignofthepowerhouseanditsequipment.Inothercases,civilengineersareassignedtoworkonaprojectinanotherfield;inthespaceprogram,forinstance,civilengineerswerenecessaryinthedesignandconstructionofsuchstructuresaslaunchingpadsandrocketstoragefacilities.Constructionisacomplicatedprocessonalmostallengineeringprojects.Itinvolvesschedulingtheworkandutilizingtheequipmentandthematerialssothatcostsarekeptaslowaspossible.Saftyfactorsmustalsobetakenintoaccount,sinceconstructioncanbeverydangerous.Manycivilengineersthereforespecializeintheconstructionphase.11许多土木工程师在设计领域工作,他们中的许多人是这个行业的佼佼者。正如我们所见，土木工程师研究许多不同的结构,因此工程师专门研究一类结构是通常的做法（一般的惯例）。在建筑设计中,工程师经常作为建筑或结构公司的顾问。水坝、桥梁、给水系统,和其它大项目通常；聘用几位系统工程师（总工程师），他们的工作是协助负责整个项目。在许多情况下,也需要（涉及）其它学科的工程师。例如,在水坝项目中,电子和机械工程师负责发电站及其设备的设计。在其它情况下,土木工程师被分配到其它领域的项目上工作;例如,在空间项目中,需要土木工程师设计和施工诸如发射台和火箭存贮设施这样的结构。12在几乎所有土木工程项目中，施工是复杂的过程。它包括项目的进度安排和设备的使用以及材料，以便使得造价尽可能降低。必须考虑安全因素，因为施工很危险。许多土木工程师因此专门研究施工阶段。Lesson2ModernBuildingsAndStructuralMaterialsToday,however,theengineerhastheadvantagenotonlyofempiricalinformation,butalsoofscientificdatathatpermithimtomakecarefulcalculationsinadvance.Whenamodernengineerplansastructure,hetakesintoaccountthetotalweightofallitscomponentmaterials.Thisiskonwnasthedeadload,whichistheweightofthestructureitself.Hemustalsoconsidertheliveload,theweightofallthepeople,cars,furniture,machinesandsoonthatthestructurewillsupportwhenitisinuse.Instructuressuchasbridgesthatwillhandlefastautomobiletraffic,hemustconsidertheimpact,theforceatwhichtheliveloadwillbeexertedonthestructure.Hemustalsodeterminethesafetyfactor,thatis,anadditionalcapabilitytomakethestructurestrongerthanthecombinationofthethreeoftenfactors.Theprincipleconstructionmaterialsofearliertimeswerewoodandmasonrybrick,stone,ortile,andsimilarmaterials.Thecoursesorlayerswereboundtogetherwithmortarorbitumen,atarlikesubstance,orsomeotherbindingagent.TheGreeksandRomanssometimesusedironrodsorclampstostrengthentheirbuildings.ThecolumnsoftheParthenoninAthens,forexample,haveholesdrilledinthemforironbarsthathavenowrustedaway.TheRomansalsousedanaturalcementcallespozzolana,madefromvolcanicash,thatbecameashardasstoneunderwater.3但是，现在的工程师具备许多有利条件，不仅有经验资料，而且有科学数据供他预先做详细计算。一个现代工程师当他设计一座建筑物时，他要考虑这座建筑物所有组成材料的总重量，这就是所谓的静荷载，即建筑物自身的重量。他还必须考虑动荷载，即在建筑物投入使用时它要承受的人，车辆，设备、机器等等的重量。对于象桥梁这种需要承担高速汽车交通的构筑物，他必须考虑到冲力，即动荷载将借以作用于结构物的那种力。他还必须确定出安全系数，即附加的承载能力，以使建筑物的承载能力比上述三个因素结合起来还要强些。7现代最引人注目的工程事故之一——1940年塔科马海峡大桥的倒塌，就是由于没有非常仔细地考虑这些因素中的最后一个因素。在一场暴风雨中，当每小时高达65公里的强劲狂风冲击这座桥时，狂风引起了沿着桥面方向的波动；同时还产生了一种使路面塌落的横向运动。幸亏工程师们从错误中汲取了教训，所以现在的通常做法是将按比例缩小的桥梁模型放在风洞中检验它们的空气动力学抵抗力。Lesson5philosophyofstructuraldesignSpecially,thestructuraldesignofanystructurefirstinvolvestheestablishmentoftheloadingandotherdesignconditionsthatmustberesistedbythestructureandthereformustbeconsideredinitsdesign.Thencomestheanalysis(orcomputation)oftheinternalgrossforces(thrust,shears,bendingmomentsandtwistingmoments),stressintensities,strains,deflectionsandreactionsproducedbytheloads,temperature,shrinkage,creep,orotherdesignconditions.Finallycomestheproportioningandselectionofmaterialsofthemembersandconnectionssoastoresistadequatelytheeffectsproducedbythedesignconditions.Thecriteriausedtojudgewhetherparticularproportionswillresultinthedesiredbehaviorreflectaccumulatedknowledge(theory,fieldandmodeltests,andpracticalexperience),intuitionandjudgment.Formostcommoncivilengineeringstructuressuchasbridgesandbuildings,theusualpracticeinthepasthasbeentodesignonthebasisofacomparisonofallowablestressintensitieswiththoseproducedbytheserviceloadingsandotherdesignconditions.Thistraditionalbasisfordesigniscalledelasticdesignbecausetheallowingtotheyieldpointofthematerialshouldnotbeexceededatthemosthighlystressedpointsofthestructure.Ofcourse,theselectionoftheallowablestressesmayalsobemodifiedbyaconsiderationofthepossibilityoffailureduetofatigue,buckling,orbrittlefractureorbyconsiderationofthepermissibledeflectionsofthestructure.Theallowance-stressapproachhasanimprotantdisadvantageinwhichitdoesnotprovideauniformoverloadcapacityforallpartsandalltypesofstructures.Asaresult,thereistodayarapidlygrowingtendencytobasethedesignontheultimatestrengthandserviceabilityofthestructure,withtheolderallowable-stressapproachservingasanalternativebasisfordesignthenewerapproachcurrentlygoesunderthenameofstrengthdesigninreinforce-concrete-designliteratureandplasticdesigninsteel-designliterature.Whenproportioningisdoneonthestrengthbasis,theanticipatedserviceloadingisfirstmultiplied