土木工程专业英语(第二版-段兵延)第7课.pptx

Lesson7Bridge桥梁,Newwordsandphrases:valleyn.(山)谷，流域obstaclen.障碍，妨害物aqueductn.沟渠，导水管pedestriann.步行者adj.徒步的，呆板的，通俗的bargen.驳船，游艇vt.用船运输vi.蹒跚，闯入isolatedadj.隔离的，孤立的，单独logn.航行日志，原木，园形木材,园木v.把.记入航行日志，伐木，把.锯成段vinen.葡萄树，蔓生植物，攀缘植物，藤，蔓slantv.(使)倾斜，歪向n.倾斜swiftn.鸟雨燕，(梳棉机等的)大滚筒adj.迅速的,敏捷的,立刻的adv.迅速地,敏捷地subsoiln.底土,下层土,天然地基v.掘起.的底土,Newwordsandphrases,gapn.缺口,裂口,间隙,缝隙,差距,隔阂aerialistn.高空杂技师tightropen.拉紧的绳索cablen.电缆,海底电报,缆,索v.打(海底)电报abutmentn.邻接,桥礅，桥台，拱座Anchorage锚地；碇泊处；靠山；寄托stretchv.伸展,伸长n.一段时间,一段路程,伸展girdern.梁,钢桁的支架overlapv.(与.)交迭intersectvt.横断vi.(直线)相交,交叉corbelarch突拱intermediatepier中间墩,1.valley谷，河谷，山谷；流域如：theYangtzevalley长江流域2.obstacle障碍，障碍物如：Herparentsoppositionisanobstacletohermarriage.8.vine葡萄树grape葡萄wine葡萄酒Wineismadefromgrapes.12.gap缺口，缝隙generationgap代沟14.tightrope拉紧的绳索tightrope20.overlap重叠，搭接overlaplap重叠，包围,Words,Bridgeisastructurethatspansobstacles,suchasriversandvalleys,toprovidearoadwayfortraffic.桥梁是跨越障碍（比如河流和峡谷）的结构物，为通行提供道路。Byfarthemajorityofbridgesaredesignedtocarryautomobileorrailroadtraffic,butsomeareintendedforpedestriansonly.到目前为止，大多数桥梁是被设计用来承担汽车和铁路交通，但是也有一些是只供行人通行。Anumberofaqueductbridges,mostlyerectedinEuropeinthe19thcentury,carrycanalsandtheirbargetraffic；andatleastonebridge,atNewYorkCitysKennedyAirPort,servestocarrytaxyingaircraftoverahighway.许多沟渠桥梁承担起了沟渠和驳船交通，这些桥梁大多数修建于19世纪的欧洲；其中至少有一座，在纽约的肯尼迪机场，是用来在公路上方运送滑行的飞机。,Bridge,aqueductbridges,Thefirstbridgesbuiltbymanprobablyresembledthosestillbeingconstructedbyprimitivepeoplesinisolatedregions.人类修建的第一批桥梁可能类似于那些在与世隔绝的地区原始人还在修建的桥梁。Thetoolsandbuildingskillsofearlyman,likethoseofprimitivepeoplestoday,weresoelementarythathewasundoubtedlyforcedtouseeasilytransportablematerialsthatcouldbeputinplacewithaminimumofformingandshaping.早期人类使用的工具和建桥的技术就像原始人类的一样低级，以至于无庸置疑地他得被迫使用容易运输的材料，这些材料经过少许的加工成形和修整即可实施安装。,Bridge,Inforestregions,wherestouttimbersorlogscouldbeobtained,bridgesverylikelyweremadeofoneormoreparallellogs,possiblycoveredwithcrossbranchesormattingforbetterfooting.在森林区，有粗壮的木材或圆木可利用，桥梁很可能用一根或几根平行的圆木建造而成，为了更好的行走可能会在上面铺上交叉的树枝或草席。IntropicalregionsofIndia,Africa,andSouthAmerica,fibrousvineswereusedtobuildsuspensionbridges.在印度、非洲和南美洲的热带地区，含纤维的藤条被用来修建吊桥。Thevinesweretiedtotreesorrocksoneachsideofthestreamorvalleytobecrossed.Oneormorevineswereusedtotreadon.Othervines,strungseveralfeethigher,wereusedforhandholds.藤条被系在要跨越的溪流和峡谷两边的树木或岩石上。一根或几根藤条被用来行走。其它的则排列在几英尺高的地方，作扶手用。,Bridge,Althoughvinebridgesareusuallyunstable,somebuiltbytheIncaswerestrongandstableenoughtobeusedbytheinvadingSpanishsoldiersandtheirhorses.虽然藤桥通常不稳定，但是由印加人修建的一些藤桥却足够坚固和稳定，以至于入侵的西班牙士兵和他们的马匹通行无碍。Inrockyregions,stonewasusedforbridges.在多岩石的地区，石头被用来修桥。Pilesofstonewereplacedatshortintervalsacrosstheriver,providingthebridgepiers,andthenapathfrombanktobankwasmadebylayingflatstoneslabsacrossadjacentpiers.横跨河流以很小的间距布置石堆作为桥墩，然后用平石板横过相邻的桥墩就建成连接两岸的通道。,Bridge,Afewstonebridgesofthistype,calledclapperbridges,canstillbeseeninDartmoor,England；however,theydateonlyfromtheMiddleAgesorevenlater.这种类型的一些石桥，被称为clapperbridges，仍然能在英国的达特姆尔高原发现；但是，它们却只始于中世纪或更晚。ThefirstinnovationbeyondtheprimitivebridgeformsisbelievedtohaveoccurredinancientChinaandthenspreadtoIndia.超出原始桥梁形式的第一次革新被认为发生在古代中国，然后传到了印度。,Bridge,clapperbridge,clapperbridge,Tobridgestreamswiderthanasingletreelength,theChineseandIndiansusedtwopilesoftreetrunks,buildingtowardthestreamcenterfromeachbank.为了在比一根树木的长度更宽的河流上架桥，中国人和印度人用两堆树干，从河两岸向中心修建。Ineacharmofthestructure,thelogswerepiledontopofoneanotherwithaslightupwardslant,witheachlayerprojectedseveralfeetbeyondtheoneimmediatelybelowit.在结构的每一边，圆木都被稍微向上倾斜着堆在另一根的顶上，每一层都比其下面的一层伸出去几英尺。Forstability,eachpileoftimberswasanchoredbyamassivepileofstoneoneachbank.为了稳定，每堆木材都用一大堆石头锚固在每一岸边。,Bridge,Nearmidstream,thegapbetweentheendsofthearmswasclosedbytheadditionofasinglebeambetweenthetwoends.Inthiskindofstructure,acrudecantileverbridge,theachievablespanlengthismadegreaterbytheadditionofacentralsectionbetweenthefreeendsofarms.接近河中央，两个臂端之间的缺口用简支梁（单跨梁）连接。在这种结构中，在两个悬臂中间增加一个中间构件便成为跨度较大的天然悬臂桥。Asearlyas4000B.C.inMesopotamiaand3400B.C.inEgypt,overlappinghorizontallayersofstoneorsun-bakedbrickwereusedinsteadofoverlappingtimbers.早在公元前4000年的esopotamia和在公元前3000年的埃及，用水平交叉搭接的石板或太阳晒干的砖被用来取代交叉搭接的木材。,Bridge,Thisconstruction,whichlookslikeamasonryarchthatissteppedratherthansmoothontheundersideiscalledacorbeledarch.这种结构被称为突拱，它看起来象一个下面是阶梯状而非光滑的石拱。Tochangethecorbeledarchintoatruearch,itwasonlynecessarytoreorienttheinnerstonessothattheyformedasmoothcurve.为了把突拱变成真正的拱，只需要重新调整内部的石头以便于它们形成一条光滑的曲线。Thetruearch,whichwasusedasearlyas3500B.C.,ismuchstrongerthanthecorbelledarch.早在公元前3500年被使用的真正的拱比突拱牢固得多。Thetruemasonryarchwasefficient,economical,anddurable.真正的石拱是高效、经济和耐用的。,Bridge,corbeledarch,Itcouldspansmallriversbymultiplearchesrestingonpiers;moreover,itwasgenerallygraciousinappearance.它能通过放置在桥墩上的多拱跨越一些小河；而且，它通常在外观是很优美的。Thesequalitieswerehardtomatchbyanypreviousformofconstruction.以前任何一种构造形式其品质都很难与之相媲美。ThetruemasonryarchwaswidelyusedinbridgeconstructionbyboththeancientChineseandtheRomans;itremainedinwideuseuntilthe19thcentury.真正的石拱被广泛地应用于古代中国和罗马的桥梁结构中；在19世纪以前也一直被广泛应用。Basicallytherearejustfourtypesofstructuresthatcanbeusedtobridgeastreamorotherobstacle:rigidbeams,cantilevers,arches,andsuspensionsystems.主要有4种基本类型的结构能够被用来跨越河流或其它障碍：刚性梁、悬臂、拱和悬索体系。,Bridge,RigidBeam刚梁,Thesimplestwayandprobablythefirstusedistolayarigidbeamacrossthestreamsothatitstwoendsrestonoppositebanks.最简单的方式，也可能是最早被使用的方式，就是放置一根刚性梁横跨河流，这样它的两端被搁置在对面的岸上。Therigidbeaminthistypeofbridgemaybeashapedwoodenbeam,agirderofsteelorconcrete,orevenacomplextruss.这类桥梁中的刚梁可能是成型的木梁，也可能是钢梁或混凝土梁，甚至可能是复杂的桁架。Thespanofarigidbeamtypeofbridgecanbeincreasedbybuildingintermediatepiersandbridgingthegapsbetweenthepierswithseveralbeams.通过修建中间桥墩和用几根梁跨越桥墩间间隔的方法可以增加刚性梁类桥梁的跨距。,RigidBeam刚梁,Thematerialsusedforrigidbeamsmustbeabletowithstandbothcompressionandtension.用作刚梁的材料必须既能承担压力也能承担拉力。Thedoublerequirementstemsfromthefactthatwhenaloadisplacedonarigidbeam,thebeambendsinspiteofitsname.这种双重要求来自于这样一个事实：当一个荷载被放到刚性梁上时，梁会弯曲尽管它的名字叫刚性梁。Asaresultofbendingtheupperpartofthebeamiscompressedandthelowerhalfisstretched.弯曲的结果是梁的上部受压，下部受拉。Ifitscompressivestrengthistoolow,itwillbuckle；ifitstensilestrengthistoolow,itwillbreak.如果它的抗压强度太低，那么它将翘曲；如果它的抗拉强度太低，那么它将折断。,Cantilever悬臂,Oftenitisnotfeasibletoconstructlongspanbridgesbymeansofintermediatepiers.通常用中间桥墩的办法修建长跨距的桥梁并不可行。Indeepswift-runningriversorinsoftsubsoils,forexample,itmaybedifficulttoconstructthepiersortomakethemdeepenoughtoreachafirmfoundationrock.比如，在又深又急的河流中或软土地基中，可能很难修建桥墩或将桥墩做得足够深以到达坚硬的基岩。Insuchcasesthespanofarigid-beamstructurecanbeextendedsimplybyusingtwobeamsoneextendingfromeachbankwithoneendofeachbeamfirmlyanchoredtoitsfoundation,ratherthansimplyrestingonitasinordinaryrigid-beamconstruction.在这种情况下，刚梁结构的跨距能简单地通过使用两根梁进行延伸（每一根从每一岸延伸出来），每根梁的端部都被牢固地锚固在基础上，而不是像普通的刚梁结构简单地搁置在基础上。,Cantilever悬臂,Eachoftheanchoredbeamsinthiskindofstructureiscalledacantilever.在这种类型结构中每一根锚固的梁就被称为悬臂。Perhapsthesimplestfamiliarexampleofasinglecantileveristhefamiliardivingboard.可能一个单一悬臂的最简单又熟悉的例子是常见的跳水板。Inanordinarycantileverbridge,thegapbetweentheendsofthecantileversisclosed,providingacontinuousdeckfortheroadway,butifthebridgewerecutintwoatthepointofclosureeachcantileverwouldsupportitself.在普通的悬臂式桥梁中，悬臂梁端部之间的间隙是闭合的，为道路提供了连续的桥面，但是假如把这种桥梁在其闭合点断开，那么每一根悬臂梁都不需另外设置支撑而可保持稳定。Usuallythegapbetweenthecantileversisclosedbymeansofarigidbeam,thusextendingthespanofthecantilevers.通常悬臂之间的间隙是用一根刚梁闭合的，这样又增加了悬臂的跨距。,divingboard,cantileverbridge,SuspensionBridge,Suspension悬索,Suspensionbridgescanspanevengreaterdistanceswithoutintermediatepiersthancancantileverbridges.Thesupportingmembersofasuspensionbridgearecontinuousflexiblecables,witheachcableanchoredatbothofitsends.与悬臂桥相比，在没有中间桥墩的情况下，悬索桥能跨越更远的距离。悬索桥的支撑构件是连续的柔韧的缆索，每根缆索的两端都要锚固。Thesimplestexampleofthesuspensionbridgeisthecircusaerialiststightrope,andprimitivesuspensionbridgeswereoftennomorethanseveralsuchtightropestiedtogethertoprovidebothhandandfootholds.悬索桥最简单的例子是杂技场高空杂技演员走钢丝用的钢丝，原始的悬索桥常常是把很少的几根这样的钢丝系在一起来提供扶手和立足点的。Inmodernsuspensionbridgesalevelroadwayisprovidedbystringingthecablesoverheadonhightowersandsuspendingtheseparateroadwaybelow.在现代悬索桥梁中，平坦的路面是由挂在高塔上的一排缆索及缆索下方悬挂着的相互隔开的车道组成。,ArchBridgeZhaozhouBride,Arch拱,Thearchisinasensetheoppositeofasuspensioncable.在某种意义上说，拱正好和悬索的缆相对应。Wherethesuspensioncablehangsfreelyfromitssupportingtowers,thearchcurvesrigidlyupwardfromitsabutments.在悬索从它的支撑塔自由地悬挂起来的地方，拱就在它的桥台以上弯成刚性曲形。Becauseofthisdifferenceinshape,thesuspensioncabletendstopullitsanchoragestogether,whilethearchtendstopushitsabutmentsapart.因为形式的不同，悬索趋向于将它的锚固点拉到一起，而拱则趋向于将它的桥台向两边推开。Forthisreasonsuspensioncablesmustbeabletowithstandstretching,whilearchesmustbemadeofmaterialsthatcanwithstandcompression.因为这个原因，悬索必须能承担拉力，而拱必须用能承担压力的材料制造。,Arch拱,Becausetensilestrengthisnotnecessarilyrequiredforarchconstruction,archbridgescanbemadeofbricksorstoneblocksthatareheldtogetherbythecompressiveforcecharacteristicofthearch.因为拱结构不必要求材料具有抗拉强度，所以拱桥可以用砖或石块建造，砖或石块通过拱传递