土木工程专业英语LESSON.ppt

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1、Lesson7Bridge课程学习指南：课程学习指南：1.wordslearningPedestrian(行人行人)ped(pod，词根，词根)-足足pedal(足的，脚的、足的，脚的、脚踏脚踏)Subsoil(底土底土)=sub（前缀：下、次）（前缀：下、次）+soilOverlap(重叠，搭接重叠，搭接)=over(前缀：前缀：=super)+lap(接接)Intersect(交叉交叉)=inter(前缀：相互之间前缀：相互之间的的)+sect(段、部分段、部分=part)Bridge is a structure that spansobstacles,such as rivers an

2、d valleys,toprovide a roadway for traffic.By far themajority of bridgesare designedto carryautomobileorrailroadtraffic,butsomeareintendedforpedestriansonly.pedestriannounapersonwalkingalongaroadorinabuilt-uparea步行者，行人adjectivelackinginspirationorexcitement;dull缺乏想像力的，平淡无奇的，乏味的为提供交通道路，桥梁是跨越如河流、山谷为提供交

3、通道路，桥梁是跨越如河流、山谷这样障碍的一种结构形式，到目前为止，大这样障碍的一种结构形式，到目前为止，大部分桥梁都是公路桥或铁路桥，仅有少部分部分桥梁都是公路桥或铁路桥，仅有少部分是人行桥。是人行桥。A number of aqueduct bridges,mostlyerected in Europe in the 19th century,carrycanals and their barge traffic;and at least onebridge,at New York Citys Kennedy Airport,servestocarrytaxyingaircraftovera

4、highway.aqueductbridge高架水渠高架水渠verb(taxis,taxied,taxiingortaxying)(intransitive)(ofanaircraft)moveslowlyalong the ground before takeoffor afterlanding:the planetaxisuptoawaitingcar.takeataxiasameansoftransport:Iwouldtaxihomeandsleeptilleight.大大量量的的高高架架渠渠桥桥于于19世世纪纪在在欧欧洲洲建建成成，以以保保证证运运河河和和船船舶舶交交通通的的运运行行

5、。最最小小的的一一座座桥桥在在纽纽约约市市的的肯肯尼尼迪迪机机场，它主要是把滑行飞机拖到跑道上服务的。场，它主要是把滑行飞机拖到跑道上服务的。The first bridges built by man probablyresembledthosestillbeingconstructedbyprimitivepeoplesinisolatedregions.primitiveadj.原始的原始的,早期的简单的早期的简单的;粗糙的原始人粗糙的原始人,原始事物原始事物人类建成的首批桥类似于原始人在孤立地带建成的桥。人类建成的首批桥类似于原始人在孤立地带建成的桥。The tools and bui

6、lding skills of early man,likethoseofprimitivepeoplestoday,wereso elementary that he was undoubtedlyforcedtouseeasilytransportablematerialsthatcouldbeputinplacewithaminimumofformingandshaping.早早期期人人类类的的工工具具和和建建筑筑技技术术如如同同原原始始人人类类一一样样都都是是最最初初级的，只有应用经过简单加工成型的材料。级的，只有应用经过简单加工成型的材料。In forest regions,wher

7、e stouttimbers or logs could be obtained,bridgesverylikelyweremadeofonemore parallel logs,possibly coveredwith cross branches or matting forbetterfooting.stout结实的；厚实的结实的；厚实的在在森森林林里里，随随处处可可得得结结实实的的木木材材，那那时时侯侯的的桥桥极极可可能能是是由由并并排排的的几几根根圆圆木木建建成成，可可能能在在其其上上覆覆一些木枝或草垫以方便行走。一些木枝或草垫以方便行走。In tropical regions of

8、 India,Africa,and SouthAmerica,fibrousvineswereusedtobuildsuspensionbridges.Thevinesweretiedtotreesorrocks on each side of the stream or valley to becrossed.Oneormorevineswereusedtotreadon.Othervines,strungseveralfeethigher,wereusedforhandholds.streamvalley河谷河谷处处于于热热带带地地区区的的印印度度、非非洲洲、和和南南美美洲洲，纤纤维维藤藤

9、用用来来建建成成悬悬索索桥桥，这这些些藤藤系系在在小小河河或或山山谷谷两两边边的的树树上上或或岩岩石石上上，一一根根或或更更多多的的藤藤用用于于在在上上面面行行走走，其其它它的的在在几几英英尺尺高高的的地地方，用作扶手用。方，用作扶手用。Although vine ridges are usually unstable,somebuiltbytheIncaswerestrongandstableenoughtobe used by the invading Spanish soldiers andhorses.invade侵侵入入;侵侵略略(别别国国);侵侵犯犯(主主权权等等)拥拥入入;挤挤满

10、满Thetownwasinvadedbyacrowdoftourists.虽虽然然藤藤索索桥桥通通常常不不稳稳定定，但但印印加加人人建建成成的的藤藤索索桥桥足足够够的的坚坚固固和和稳稳定定性性，被被用用于于西西班班牙牙士士兵兵和和他他们们马马匹匹的的通行。通行。Inrockyregions,stonewasusedforbridges.Piles of stone were placed at short intervalsacrosstheriver,providingthebridgepiers,andthen a path front bank to bank was made byla

11、yingflatstoneslabsacrossadjacentpiers.Afew stone bridges of this type,called clapperbridges,canstillbeseeninDartmoor,England;however,theydateonlyfromtheMiddleAgesorevenlater.在在岩岩石石地地区区，石石头头被被用用来来建建桥桥，横横跨跨河河流流以以很很小小的的间间距距布布置置石石碓碓作作为为桥桥墩墩，然然后后用用平平坦坦的的石石头头跨跨过过相相邻邻的的桥桥墩墩就就建建成成连连接接两两岸岸的的通通道道，大大部部分分的的石石桥桥

12、就就是是这这种种类类型型，叫叫做做鼓鼓掌掌桥桥。现现在在在在Dartmoor、英英格格兰兰仍仍然然可见，不过它们都建于中世纪甚至更晚。可见，不过它们都建于中世纪甚至更晚。Thefirstinnovationbeyondtheprimitive bridge forms is believed tohave occurred in ancient China andthenspreadtoIndia.Tobridgestreamwider than a single tree length,theChineseandIndiansusedtwopilesofthreetrunks,buildin

13、gtowardthestreamcenterfromeachbank.pile桩桩，一堆，一叠，一堆，一叠原原始始桥桥梁梁的的第第一一步步变变革革被被认认为为出出现现在在中中国国古古代代，随随后后传传入入印印度度。河河床床一一般般比比树树要要宽宽，中中国国人人和和印印度度人人从从河河的的两两岸岸到到河河中中央央用用两两堆堆树树干来建造。干来建造。In each arm of the structure,the logs werepiled on top of one another with a slightupward slant,with each layer projectedsever

14、al feet beyond the one immediatelybelowit.For stability,eachpileof timberswasanchoredbyamassivepileofstoneoneach bank.Near midstream,the gapbetweentheendsofthearmswasclosedbytheadditionofasimplebeambetweenthetwoends.每每个个分分支支中中，圆圆木木一一个个接接一一个个的的布布置置并并微微微微向向上上倾倾斜斜，使使其其每每一一层层都都比比它它下下面面的的高高几几英英尺尺。为为了了增增加

15、加稳稳定定性性，每每个个木木桩桩在在两两岸岸都都用用一一堆堆大大而而重重的的石石头头锚锚固固；接接近近河河中中央央，在在河河中中间间的的两两个个分分支支的的两两端则用简支梁连接。端则用简支梁连接。In this kind of structure,a crude cantileverbridge,theachievablespanlengthismadegreaterbytheadditionofacentralsectionbetweenthefreeendsofthearms.crude天天然然的的,未未加加工工的的，简简陋陋的的,粗粗糙糙的的,未未加加修修饰饰，粗粗鲁鲁的的,粗粗俗俗的的

16、,粗野的粗野的在在这这种种结结构构中中，天天然然支支架架桥桥在在两两个个分分支支的的两两端端加加上上额外构件后可达到很宽的跨度。额外构件后可达到很宽的跨度。As early as 4000 B.C.in Mesopotamia and 3000B.C.inEgypt,overlappinghorizontallayersofstone or sun-baked brick were used instead ofoverlappingtimbers.早早在在公公元元前前4000年年的的esopotamia和和在在公公元元前前3000年年的的埃埃及及，用用石石头头或或日日光光烤烤干干的的砖砖代代

17、替替木木头头被被用用于横向覆盖层。于横向覆盖层。thisconstruction,whichlookslikeamasonryarchthat is stepped rather than smooth on theundersideiscalledacorbeledarch这种结构看起来像的砖拱，一层层铺起，被叫做突拱。这种结构看起来像的砖拱，一层层铺起，被叫做突拱。T0changethecorbeledarchintoatruearch,itwasonly necessary to reorient the inner stones sothattheyformedasmoothcurve

18、.要要使使突突拱拱变变为为真真正正的的拱拱，需需要要调调整整内内部部石石头头的的构构造造以以形形成光滑的曲面。成光滑的曲面。Thetruearch，whichwasusedasearlyas3500B.C.,ismuchstrongerthanthecorbeledarch.这种拱比突拱更坚固，且早在公元前这种拱比突拱更坚固，且早在公元前500年就被使用。年就被使用。Thetruemasonryarchwasefficient,economical,and durable.It could span small rivers bymultiple arches resting on piers

19、;moreover,itwasgenerallygraciousinappearance.这这种种石石拱拱经经济济和和经经久久耐耐用用，它它可可以以由由多多个个跨跨过过桥桥墩墩的的拱拱而跨过小的河流，而且外观非常漂亮。而跨过小的河流，而且外观非常漂亮。These qualities were hard to match by anypreviousformofconstruction.Thetruemasonryarchwaswidelyusedinbridgeconstructionbyboth the ancient Chinese and the Romans;itremainedinw

20、ideuseuntilthe19thcentury.而而它它的的质质量量比比先先前前的的任任何何结结构构都都要要好好。在在中中国国和和罗罗马马的的古古代代，这这种种整整体体石石拱拱被被广广泛泛地地用用于于桥桥梁梁结结构构。它它一一直直被广泛地使用直到被广泛地使用直到19世纪。世纪。Basicallytherearejustfourtypesofstructuresthat can be used to bridge a stream or otherobstacle:rigid beams,cantilevers,arches,andsuspensionsystems.通通常常用用作作河河流流

21、或或障障碍碍物物上上的的桥桥，有有4类类基基本本结结构构：刚性梁、悬臂、拱、和悬索体系。刚性梁、悬臂、拱、和悬索体系。RigidBeam.Thesimplestway一一andprobablythefirstused一一istolayarigidbeamacrossthestream so that its two ends rest on oppositebanks.刚刚性性梁梁.最最简简单单也也可可能能是是最最早早使使用用的的刚刚性性梁梁布布置置在在河流上，两端固定在河的两岸。河流上，两端固定在河的两岸。Therigidbeaminthistypeofbridgemaybeashaped

22、wooden beam,a girder of steel orconcrete,orevenacomplextruss.桥桥的的刚刚性性梁梁可可以以是是某某种种形形状状的的木木梁梁、钢钢筋筋混混凝凝土土梁梁或复杂的绗架。或复杂的绗架。Thespanofarigidbeamtypeofbridgecanbeincreased by building Intermediate piers andbridgingthegapsbetweenthepierswithseveralbeams.采采用用在在中中间间建建桥桥墩墩或或用用几几根根横横梁梁连连接接间间隙隙的的方方法法，可以增加桥可以增加桥刚性

23、梁刚性梁的跨度。的跨度。The materials used for rigid beams must beable to withstand both compression and tension.刚性梁的材料必须能够承担压力和拉力，刚性梁的材料必须能够承担压力和拉力，Thedoublerequirementstemsfromthefactthatwhenaloadisplacedonarigidbeam,thebeambends-inspiteofitsname.这种双重要求源于梁在荷载作用会产生弯曲。这种双重要求源于梁在荷载作用会产生弯曲。Asaresultofbendingtheup

24、perpartofthebeamiscompressedandthelowerhalfisstretched.弯曲的结果，使梁上部受压，下部受拉，弯曲的结果，使梁上部受压，下部受拉，If its compressive strength is too low,it willbuckle;if its tensile strength is too low,it willbreak.如如果果它它的的受受压压承承载载力力太太弱弱，它它将将会会屈屈曲曲，如如果果受受拉拉承承载力太弱，他将会拉断。载力太弱，他将会拉断。Cantilever.Often it is not feasible to con

25、structlong span bridges by means of intermediatepiers.In deep swift-running rivers or in softsubsoil,for example,it may be difficult toconstruct the piers or to make them deepenoughtoreachafirmfoundationrock.悬悬臂臂。利利用用中中间间桥桥墩墩方方式式，建建造造大大跨跨度度桥桥通通常常是是不不可可行行的的。举举个个例例子子，在在深深而而流流速速急急的的河河流流或或软软泥泥中中，很很难建造墩使

26、它有足够深度达到基岩层。难建造墩使它有足够深度达到基岩层。Insuchcasesthespanofarigid-beamstructurecanbeextendedsimplybyusingtwobeams-oneextendingfromeachbankwithoneendofeachbeam firmly anchored to its foundation,ratherthan simply resting on it as in ordinary rigid-beamconstruction.在在这这种种情情况况下下，刚刚性性梁梁结结构构用用两两根根梁梁就就可可以以延延伸伸从从每每岸岸

27、伸伸出出一一根根梁梁而而在在两两根根梁梁的的端端部部基基础础进进行行锚锚固，这一点与普通刚性梁不同。固，这一点与普通刚性梁不同。Eachoftheanchoredbeamsinthiskindofstructureiscalled a cantilever.Perhaps the simplest familiarexample of a single cantilever is the familiar divingboard.每每一一根根锚锚固固的的梁梁称称之之为为悬悬臂臂，或或许许这这种种最最简简单单而而熟熟悉悉的的悬悬臂臂例例子便是跳水板。子便是跳水板。In an ordinary c

28、antilever bridge,the gap between theends of the cantilevers is closed,providing acontinuousdeckfortheroadway,butifthebridgewerecutintwoatthepointofclosureeachcantileverwouldsupportitself.在在普普通通的的悬悬臂臂式式桥桥梁梁中中，悬悬臂臂梁梁端端部部之之间间的的间间隙隙是是闭闭合合的的，为为道道路路提提供供了了连连续续的的桥桥面面。但但是是假假如如把把这这种种桥桥梁梁在在其其闭闭合合点点断断开，那么每一根悬臂梁

29、都不需要另外设置支撑而可保持稳定。开，那么每一根悬臂梁都不需要另外设置支撑而可保持稳定。Usually the gap between the cantilevers is closed bymeansofarigidbeam,thusextendingthespanofthecantilevers.通通常常悬悬臂臂梁梁中中间间间间隙隙使使用用刚刚性性梁梁来来闭闭合合，这这样样，可可延延伸伸悬悬臂臂梁梁的跨度。的跨度。Suspension.Suspension bridges can spaneven greater distances without intermediatepierstha

30、ncancantileverbridges.悬悬索索。在在没没有有中中间间桥桥墩墩的的情情况况下下，悬悬索索桥桥比比悬悬臂臂桥桥跨跨越更大的距离。越更大的距离。The supporting members of a suspensionbridgearecontinuousflexiblecables,witheachcableanchoredatbothofitsends.悬索桥的支撑体系是两端锚固的连续可弯曲的缆绳。悬索桥的支撑体系是两端锚固的连续可弯曲的缆绳。The simplest example of the suspensionbridge is the circus aerial

31、ists tightrope,andprimitivesuspensionbridgeswereoftennomorethan several such tightropes tied together toprovidebothhandandfootholds.悬悬索索桥桥最最简简单单的的例例子子是是杂杂技技场场高高空空走走钢钢丝丝杂杂技技演演员员用用的的钢钢丝丝。原原始始的的悬悬索索桥桥常常常常是是一一把把很很小小的的几几根根这这样样的的钢丝系在一起来提供扶手和立足点的。钢丝系在一起来提供扶手和立足点的。Inmodernsuspensionbridgesalevelroadwayispro

32、vided by stringing the cables overhead onhigh towers and suspending the separateroadwaybelow.在现代悬索桥内，水平道路是由悬吊在高的塔架上缆在现代悬索桥内，水平道路是由悬吊在高的塔架上缆绳提供，缆绳在车行道的下面。绳提供，缆绳在车行道的下面。Arch.The arch is in a sense the opposite of asuspension cable.Where the suspension cablehangs freely from its supporting towers，thear

33、chcurvesrigidlyupwardfromitsabutments.拱拱则则是是相相反反于于悬悬索索的的作作用用，在在那那些些悬悬索索的的缆缆绳绳自自由由地地悬悬挂挂在在塔塔架架上上，拱拱却却是是从从它它的的两两端端拱拱座座处处紧紧紧紧地地向向上上弯弯曲。曲。Becauseofthisdifferenceinshape,thesuspension cable tends to pull its anchoragestogether,while the arch tends to push itsabutmentsapart.由由于于在在形形状状上上的的不不同同，悬悬索索使使锚锚固固趋趋

34、向向拉拉在在一一起起，而而拱拱的拱座则趋向于分开。的拱座则趋向于分开。Forthisreasonsuspensioncablesmustbeabletowithstandstretching,whilearchesmustbemadeofmaterialsthatcanwithstandcompression.由由于于这这些些原原因因，悬悬索索桥桥的的缆缆绳绳必必须须承承受受一一定定的的延延伸伸作作用用，而拱材料则尽可能地抵抗压缩作用。而拱材料则尽可能地抵抗压缩作用。Becausetensile strength is not necessarilyrequiredforarchconstru

35、ction,archbridgescanbemadeofbricksorstoneblocksthatareheldtogetherbythecompressiveforcecharacteristicofthearch因因为为拱拱结结构构不不一一定定要要求求材材料料具具有有抗抗拉拉强强度度，所所以以拱拱桥桥可可以以用用砖砖或或石石头头建建造造，砖砖或或石石头头通通过过拱拱传传递递压压力力的的特特性性结合在一起。结合在一起。Such materials are useless for the other basicbridgestructures.这种材料在其它的基本桥梁结构中却毫无用处。这种

36、材料在其它的基本桥梁结构中却毫无用处。In an arch bridge,the loads are transmittedverticallydownfromtheroadwayuntiltheyintersectthearchform.在在拱拱桥桥中中，荷荷载载由由公公路路上上垂垂直直传传递递下下来来，直直到到汇汇集集在在拱处。拱处。Atthearchboundarytheloadsareredirectedalongthepath of the arch,which is in a state of simplecompression.在在拱拱桥桥中中，荷荷载载由由公公路路上上垂垂直直传

37、传递递下下来来，直直到到汇汇集集在在拱拱处处。在在拱拱的的边边缘缘处处，荷荷载载便便会会改改变变力力的的传传递递路路径径，变为一种简单的受压状态。变为一种简单的受压状态。Thecompressivethrustforcesarethentransmittedtothegroundthroughtheabutmentsorpiers.Thearch,withitssimpleandelegantstructures,hasbecomeaclassicbridgeconfiguration.有压缩力的推力通过节点或墩传到地面。拱这种简单有压缩力的推力通过节点或墩传到地面。拱这种简单而优美的结构成为桥梁中的一种基本结构。而优美的结构成为桥梁中的一种基本结构。