专业英语翻译三

专业英语翻译BridgeconstructionBridgeconstructioncanpresentextraordinarydifficulties.Usuallythefoundationsforthepiersmustrestonthebedrock,andoftenunderwater.Onetechniqueforworkingintheseconditionsisbymeansofacofferdam.Pilesusuallymadeofinterlockingsteelplatesaredrivenintothewaterbed.Thewateristhenpumpedoutfromwithintheareathathasbeenenclosed.Anothertechniqueistheuseofthepneumaticcaisson.Thecaissonishugecylinderwithabottomedgethatcancutintothewaterbed..Whencompressedairispumpedintoit,thewaterisforcedout.Caissonsmustbeusedwithextremecare.Foronething,workerscanonlystayinthecompressionchamberforshortperiodsoftime.Foranother,iftheycomeuptonormalatmosphericpressuretoorapidly,theyaresubjecttothebends,orcaissondiseaseasitisalsocalled,whichisacripplingorevenfatalconditioncausedbyexcessunderconstructionbetween1867and1874,atatimewhenthedangerofworkingincompressedairwasnotfullyunderstood,fourteendeathswerecausedbythebends.Whenextrastrengthisnecessaryinthepiers,theyaresometimeskeyedintothebedrock-thatis,theyareextendeddownintothebedrock.Thismethodwasusedtostrongtidesandhighwinds,andislocatedinanearthquakezone.Thedrillingwascarriedoutunderwaterbydeep-seadivers.Wherebedrockcannotbereached,pilesaredrivenintothewaterbed.Today,thepilesinconstructionareusuallymadeofpre-stressedconcretebeams.Oneingenioustechnique,usedfortheTappanZeeBridgeacrosstheHudsonRiverinNewYork,istorestahollowconcreteboxontopofalayerofpiles.Whentheboxispumpeddry,itbecomesbuoyantenoughtosupportalargeproportionoftheweightofthebridge(seeFig.22.3)Eachtypeofbridge,indeedeachindividualbridge,presentsspecialconstructionproblems.Withsometrussbridges,thespanisfloatedintopositionafterthepiershavebeenerectedandthenraisedintoplacebymeansofjacksorcranes.Archbridgescanbeconstructedoverafalsework,ortemporaryscaffolding.Thismethodisusuallyemployedwithreinforcedconcretearchbridges.Withsteelarches,however,atechniquehasbeendevelopedwherebythefinishedsectionsareheldinplacebywiresthatsupplyacantileversupport.Cranesmovealongthetopofthearchtplacenewsectionsofsteelwhilethetensioninthecablesincreases.Withsuspensionbridges,thefoundationsandthetowersarebuiltfirst.Thenacableisrunfromtheanchorage-aconcreteblockinwhichthecableisfastened-uptothetowerandacrosstotheoppositetowerandanchorage.Awheelthatunwindswirefromareelrunsalongthiscable.Whenthereelreachestheotherside,anotherwireisplacedonit,andthewheelreturnstoitsoriginalpositiontheotherside,anotherwireisplacedonit,andthechinemovesalongthecabletocompactandtobindthem.Constructionbeginsonthedeckwhenthecablesareinplace,withworkprogressingtowardthemiddlefromeachendofthestructure.Inallmethodsofconstruction,itisnecessarytodeterminethestressesanddeformationateverystageofconstruction.ConstructionTechniquesThedecisionofhowabridgeshouldbedependsmainlyonlocalconditions.Theseincludecostofmaterial,availableequipment,allowableconstructiontimeandenvironmentalrestriction.Sinceallthesevarywithlocationandtime,thebestconstructiontechniqueforagivenstructuremayalsovary.IncrementalLaunchingorPush-outMethodInthisformofconstructionthedeskispushedacrossthespanwithhydraulicramsorwinches(fig.22.1).Decksofpre-stressedpost-tensionedpre-castsegments,steelorboxgirdershavebeenerected.Usuallyspansarelimitedto50-60mtoavoidexcessivedeflectionandcantileverstresses,althoughgreaterdistanceshavebeenbridgedbyinstallingtemporarysupporttowers.Typicallythemethodismostappropriateforlong,Multiplanbridgesintherange300-600m,but,muchshorterandlongerbridgeshavebeenconstructed.Unfortunately,thisveryeconomicalmodeofconstructioncanonlybeappliedwhenboththehorizontalandverticalalignmentsofthedeckareperfectlystraight,oralternativelyofconstantradius.Wherepushinginvolvesasmalldownwardgrade(4-5%)thenabrakingsystemshouldbeinstalledtopreventthedeckslippingawayandheavybracingisthisneededattherestrainingpiers.Bridgelaunchingdemandsverycarefulsurveyingandsettingoutwithcontinuousandprecisechecksmadeofdeckdeflections.Alightaluminumorsteellaunchingnoseformstheheadofthedecktoprovideguidanceoverthepier.SpecialTeflonorchrome-nickelsteelplatebearingsareusedtoreduceslidingfrictiontoabout5%oftheweight,thusslenderpierswouldnormallybesupplementedwithbracedcolumnstoavoidcreakingandotherdamage.Thesecolumnswouldgenerallyalsosupportthetemporaryfrictionbearingsandhelpsteerthenose.Inthecaseofpre-castconstruction,ideallysegmentshouldbecastonbedsneartheabutmentsandtransferredbyrailtothepost-tensioningbed,theactualtransportdistanceobviouslybeingkepttotheminimum.Usuallyasegmentiscastagainstthefaceofthepreviouslyconcretedunittoensureagoodfitwhenfinallygluedinplacewithanepoxyresin.Ifthisprocedureisnotadopted,gapsofapproximately500mmshouldbeleftbetweensegmentswiththereinforcementrunningthroughandsubsequentlyfilledwithconcretebeforepost-tensioningbegins.Generallyallthesegmentsarestressedtogethertoformacompleteunit,butwhenaccessorspaceontheembankmentisatapremiumitmaybenecessarytolaunchthedeckintermittentlytoallowsectionstobeaddedprogressively.Thecorrespondingpre-stressingarrangements,bothforthetemporaryandpermanentconditionswouldbemorecomplicatedandcarefulcalculationsneededatallpositions.Theprincipaladvantageofthebridge-launchingtechniqueisthesavinginfalsework,especiallyforhighdecks.Segmentscanalsobefabricatedorprecutinaprotectedenvironmentusinghighlyproductiveequipment.Forconcretesegments,typicallytwosegmentsarelayereachweekendafterpost-tensioningincrementallylaunchedatabout20mperdaydependingonthewinchingequipment.敲Specia远lRequ底iremen比tsin挤Advanc册edCon猜struct咳ionTe苗chniqu幅es强There曲areth不reeim悠portan厅tarea粗sthat忍thee焰nginee铸ringa疼ndcon为struct禁ionte垫amhas械toco摔nsider德:痰Stress影analy筛sisdu借ringc陈onstru杠ction:芬becau蹦sethe鸦loadi乖ngsan扇dsupp在ortco祖nditio据nsof工thebr薪idgea社redif穷ferent怒from凶thefi丹nished纠bridg趋e,str但esses精ineac宿hcons垂tructi乡onsta继gemus漫tbec雾alcula弱tedto亚ensur秃ethe猫safety格ofth婶estru帐cture.档Fort柄hispu称rpose,联reali怀sticc预onstru颂ction剧loads沿mustb糕eused垫ands第itepe屋rsonne摆lmust眨bein屑formed邀onal躬lthe举loadin捉glimi雹tation鼠s.Win掘dand窗temper超ature弹areus反ually牢signif黑icant瞒forco祥nstruc按tions据tages.使Camber扎ingor宽derto门obtai茂nabri宵dgewi余ththe补right栏eleva诉tion,剂there遥quired龙cambe挨roft腐hebri授dgeat劲each谜constr俊uction若stage声must筑becal拼culate坦d.It某isreq夺uired掌thatd控uecon省sidera信tionb山egive瓣ntoc崇reepa仍ndshr档inkage殖ofth蝴econc完rete.滚Thisk匪indof彩杂calcul璃ation,物altho竟ughcu涨mberso秧me,ha孟sbeen毛simpl积ified霞bythe喝useo语fcomp停uters.损Qualit烫ycont信rol:t隐hisis搂impor屑tantf俭orany腐metho糊dofc挑onstru号ction,飘buti兴tism锦oreso知fort兆hecom肢plicat车edcon米struct致ionte睬chniqu顷es.Cu罗ringo侨fconc糖rete,排postt监ension撑ing,j获ointp宪repara禽tions,篇etc.题arede拖trimen凭talto城asuc录cessfu宽lstru奏cture.锁Thed有ietpe询rsonne争lmust片bema崇deawa党reof释themi额nimum万concre摊testr条engths戴requi曲redfo末rpost夜-tensi增oning,匆form蜡remova诚l,fal形sewor贵kremo逢val,l虏aunchi师ngand贱other掌steps既ofop个eratio瑞ns.晚Genera跨llysp抖ea璃king管speak挖ing,t烘hesea捡dvance欣dcons错tructi工ontec厌hnique秋srequ布iremo帐reeng条ineeri沫ngwor倦kthan津thec垦onvent阔ional球false析workt倘ypeco毕nstruc供tion,办butth言esavi毫ngcou伤ldbe关signif民icant.灭三罚喊斯桥梁建设火醒桥建设歪在目前有一定剂的困难杜。挣秩通常脂桩乓的基础必须放棍在基岩上附而岩石议经常在水下凳。目桐在这些男环境峡条件里起作用乖的一种技术丹是僵通过一个围堰贫。邪越由婆钢板的直做成的围堰仓被敲进含水层狮。劲痰水从浮围堰里督被抽出。捡另一种技术是胶使用齿气压沉箱傍。缎廊沉箱谷是有需巨大刃脚的圆右筒，它能够进乐入河床执。荐稳当压缩的空气预被泵送入它时漠，水被排挤出咐。骗在应用沉箱的滑过程必须非常害小心菜。盐朴原因之一，工图人只能呆在假里面非常杂短时间朵。项幕对于另一个来句说如果他们太堡快的达到像正常的大气压感，温线他们受撇到非常大的压饿强叼，最容易得潜水病弟熔也当时堡也叫沉箱病末，梦有时甚至是致皂命的。这是由顺于血管中溶于另过多的氮引起梯的的。的在摆1867梢巩和颂187望4室之间在跳桥梁的罚建设伴中珍，秤百当在压缩的空剥气里工作的危央险没被完全了擦解时，趋有鸣14候起死亡事故是济由这种原因引倍起的勾寇。添当桥桩在外力贪作用进入岩层叙时，杨，盗它脚们有时嵌进那撒些基岩，茶它亩们向下延长进场入科那些基岩。班旧金山的金门滤大桥就是用这散种方法建造的暮。美漫它能用于大风爆大浪的区域，党且位于一个地忍震区域。深海粒潜水员在水下暖进行略操纵这种技术垫。航在基岩不能到暖达的区域桩被剂敲进栋含水层。今天师，陕桩胜结构上通常由收给预加压力的轰混凝土的梁做济成郑。着慎一种绳新颖的技术被穿用丛在纽约赫德森厨河上戴的扬桥姨上。将空心的盗混凝土箱放置季在群桩上，果势箱子啦里的水被抽干础的时候其受到冰的浮力能够承渠担起一定比例紫桥梁的重量。蠢桥的每种类型心，俩实际上日每座桥，嫩都有自己的施赞工方法好。盆保一些画桁辩架桥，吐它们的跨度在浪桥桩的位置确害定时已经确定州。找通过千斤顶或窝者起重机建造淘然后提高到位咱置之后，鼻桁架被放到相听应的革位置寇。豆顾拱桥夜可以通过搭架缓或者暂时的脚汉手架上方建造段。湿这种方法通常膛被用单钢筋昂混凝土拱桥牲。尖刮然而对于刚架夕拱桥来说伙，泄已经发展了一骄种新技术，这她种技术将已装材好的部分借助沫于起着支撑作肃用的钢索控制耗就位。（钢拱蔬在安装过程中协还没有合拢前抱，是两个悬臂赛。需要用钢索刺拉着这两个悬数臂以免倾倒）叔对于悬索桥，垂基础和塔葡是首先央建造凡的躲。灶巷然后梅悬索是从塔的粗锚固端的混凝绕土块胡被固定到暖另一个塔的锚群固端，糟。枝舱然后届线轴沿着找悬索移动，当溉线轴移动到另炭一端时羊。另一遗绳索抵被放在它上并宾且车轮返回它帅的原先的位置卵，缴当所有的绳索踏放置好时，另剥一种设备开始拨沿着悬索移动昆，竟并且捆他们趴。滋疏当书绳索固定好时宴，尝桥面建造的工升作也开始进行摩，满在所有的建设僚方法中美，穿确定恳每个阶段涉的应力暂和变形是必要需的羊。施工技术逗桥梁的建设大喇都取决于当地忘的条件，这些唤条件包括材料豪的价格，可利勤用的设备，工象期的长短，和内当地的地形条仓件，所有的这就些因素都随时权间和地点的变将化而变化对于歇同一个结构来票说，优秀的施圈工方法也不止这一种。顶推法施工题饱歉在这种方法中电，桥面结构被冻液压马达或者炕带液压装置的找绞车从桥跨的走一端推仁动到另一端。返桥面结构一般后是由预应力梁眯钢梁和箱梁组尊成的。通常跨室度都小装于见50~检60m刊为了避免产生蹲过大的挠度和病应力。虽然大获跨度的桥梁可话以通过设置临狮时支座来进行风安装，这种方仓法被广泛的应僻用。多跨桥可劝以达竹到旗300~舒600m仇，然而更短或缓者更长的桥正负在被