土木工程專業(yè)英語(武漢理工大學(xué)出版社)lesson.ppt

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8BridgeDesignandConstruction橋的設(shè)計與建造,1.Newwordsanalysisaccessory=access(increased)oryDerrick=fromDerrick,thesurnameofaLondonhangmanDebris=orignearly18thcent.:fromFrenchdbris,fromobsoletedbriserbreakdown,Planning.Thefirststepleadingtotheconstructionofamodernmajorbridgeisacomprehensivestudytodeterminewhetherabridgeisneeded.規(guī)劃設(shè)計現(xiàn)代重要的橋梁建造的第一步是廣泛地研究以確定橋梁的必要性。Ifitistobeahighwaybridge,intheUnitedStatesforexample，aplanningstudyisinitiatedbyastatebridgeauthority，possiblyincooperationwithlocalgovernmentorthefederalgovernment.比如：如果是美國的高速公路橋，是由州橋管理局研究規(guī)劃并確定，同時當(dāng)?shù)氐恼蚵?lián)邦政府一起參與。,Studiesaremadetoestimatetheamountofbridgetraffic,thereliefofjammedtrafficinnearbyhighwaynetwork,theeffectsontheregionaleconomy,andthecostofthebridge.橋梁的交通流量、對附近高速公路網(wǎng)交通堵塞的調(diào)劑，對當(dāng)?shù)亟?jīng)濟的影響和橋的造價等因素進行評估研究。Themeansforfinancingtheproject,suchaspublictaxesorsaleofrevenuebondsrepaidbytollcharges,areconsidered.Bondn.結(jié)合(物),粘結(jié)(劑),聯(lián)結(jié),公債,債券,合同revenuebond收益?zhèn)@就決定了工程的投資方式，如公眾收費，依靠過通行費來支付的發(fā)行債券的規(guī)模都要被考慮進來。Ifthestudiesleadtoadecisiontogoaheadwiththeproject,thelandneededforthebridgeanditsapproachesisacquiredattheselectedsite.如果研究認(rèn)為其可行信，那么橋選址和占地問題將著手處理。,Atthispoint,fieldengineeringworkisstarted.Accuratelandsurveysaremade.landsurvey土地測量在確定場地時，現(xiàn)場測繪工作開始進行，做好精確的實地測量。Tides,floodconditions，currents,andothercharacteristicsofthewaterwayarecarefullystudied.潮汐，洪水因素，水流和排水的其它的特征都要仔細(xì)研究，Boringsamplesofsoilandrockaretakenatpossiblefoundationlocations,bothonlandandunderthewater.在陸地和水下的泥土和巖石的鉆孔取樣在基礎(chǔ)可能的位置都要盡可能地進行。,Selectionofbridgedesign.橋梁設(shè)計類型的選擇Thechieffactorsindecidingwhetherabridgewillbebuiltasagirder,cantilever,truss,arch,suspension,orsomeothertypeare：(1)location；forexample,crossariver;(2)purposes;forexample,abridgeforcarryingmotorvehicles;(3)spanlength;(4)strengthofavailablematerials;(5)cost;(6)beautyandharmonywiththelocation.決定把橋建成梁、懸臂、桁架、拱、懸索或其他類型結(jié)構(gòu)的主要因素是：（1）地點，如跨越河流；（2）目的，如建橋為了方便交通；（3）跨度；（4）可用材料強度；（5）花費；（6）美觀和和諧性。,Eachtypeofbridgeismosteffectiveandeconomicalonlywithinacertainrangeofspanlengths,asshowninthefollowingtable:.每種結(jié)構(gòu)類型的橋，只有在一定跨度范圍內(nèi)，才能是最經(jīng)濟和最有效。如下表所示：,Asindicatedinthetable,thereisaconsiderableoverlapintherangeofapplicabilityofthevarioustypesInsomecases，alternativepreliminarydesignsarepreparedforseveraltypesofbridgeinordertohaveabetterbasisformakingthefinal上表表明了不同結(jié)構(gòu)類型的適用性有很多交叉的地方。在一些實例中，在不同的初步設(shè)計中，用來比較不同類型的橋是為了在最后有最好的選擇。,Selectionofmaterials材料的選擇Thebridgedesignercanselectfromanumberofmodernhigh-strengthmaterials，includingconcrete，steel，andawidevarietyofcorrosion-resistantalloysteels橋梁設(shè)計者能選用大量的現(xiàn)代高強材料，包括混泥土、鋼筋和多種耐腐蝕的合金鋼。,FortheVerrazano-NarrowsBridge，forexample，thedesignerusedatleastsevendifferentkindsofalloysteel，oneofwhichhasayieldstrengthof5000poundspersquareinch(psi)(3，515kgsqcm)anddoesnotneedtobepaintedbecauseanoxidecoatingformsonitssurfaceandinhibitscorrosioninhibit抑制,約束,化醫(yī)抑制拿Varian-Narrows大橋來說，設(shè)計者使用了七種不同的合金鋼，其中之一的合金的屈服強度為50000英鎊每平方英寸（3115kg/c）,而且不需要油漆保護，因為有一種氧化膜覆蓋在它的表面而防止腐蝕。Thedesigneralsocanselectsteelwiresforsuspensioncablesthathavetensilestrengthsupto250，000psi(17，577kgsqcm)設(shè)計者還選用鋼絲繩作為懸索，它的抗拉強度超過250000英鎊每平方英寸（17577kg/c）,Concretewithcompressivestrengthsashighas8,000psi(5625kgsqCm)cannowbeproducedforuseinbridges,anditcanbegivenhighdurabilityagainstchippingandweatheringbytheadditionofspecialchemicalagentsandcontrolofthehardeningprocess.chipping碎屑；小碎片weathering侵蝕,風(fēng)化現(xiàn)在，抗壓強度高達8000英鎊每平方英尺（562.5kg/c）的混泥土被生產(chǎn)用于橋梁工程，而且它在增加特殊化學(xué)物質(zhì)后具有很高的抗脆裂性能和抗風(fēng)化性能，Concretethathasbeenpresressedandreinforcedwithsteelwireshasatensilestrengthof250,000psi(17,577kg/sqcm).用鋼絞線加強的預(yù)應(yīng)力混凝土，其強度達到250000英鎊每平方英寸（17577kg/c）,Otherusefulmaterialsforbridgesincludealuminumalloysandwood.橋梁使用的其它材料還有鋁合金和木材。Modernstructuralaluminumalloyhaveyieldstrengthsexceeding40,000psi(2,812kg/sqcm).現(xiàn)在的鋁合金的屈服強度超過了40000每平方英寸（2818kg/c）。Laminatedstripsofwoodgluedtogethercanbemadeintobeamswithstrengthstwicethatofnaturaltimber;glue-laminatedsouthernpine,forexample,canbearworkingstressesapproaching30,000psi(210.9kg/sqcm).laminated由薄片疊成的把片狀的木條粘在一起做成的梁是自然木材強度的二倍。例如用南部松樹而膠結(jié)的梁能承受的工作應(yīng)力達到了3000英鎊每英寸（210.9kg/c）。,Analysisofforces力的分析Abridgemustresistacomplexcombinationoftension,compression,bending,shear,andtorsionforces.一座橋要抵抗一系列的合力，如拉力，壓力，剪力和扭力。Inaddition,thestructuremustprovideasafetyfactorasinsuranceagainstfailure.另外，結(jié)構(gòu)還需要一定的安全系數(shù)作為防止破壞的安全儲備。Thecalculationoftheprecisenatureoftheindividualstressesandstrainsinthestructure,calledanalysis,isperhapsthemosttechnicallycomplexaspectofbridgebuilding.對結(jié)構(gòu)的各種應(yīng)力和應(yīng)變的準(zhǔn)確特性進行計算，這就叫應(yīng)力分析，這或許是橋梁結(jié)構(gòu)中最復(fù)雜的技術(shù)。Thegoalofanalysisistodeterminealloftheforcesthatmayactoneachstructuralmember.應(yīng)力分析的目的是為了確定作用在結(jié)構(gòu)上的各種力。,Theforcesthatactonbridgestructuralmembersareproducedbytwokindsofloads-staticanddynamic.作用在橋梁結(jié)構(gòu)的力都可以分為二類荷載：動荷載和靜荷載。Thestaticload-thedeadweightofthebridgestructureitself-isusuallythegreatestload.Thedynamic,orlive,loadhascomponents,includingvehiclescarriedbythebridge,windforces,andaccumulationsoficeandsnow.靜荷載即橋的自重它往往也是最大的荷載。動荷載或靜荷載有很多，包括橋面上的機動車，風(fēng)荷載，和積冰積雪荷載。,Althoughofthetotalweightofthevehiclesmovingoverabridgeatanytimeisgenerallyasmallfractionofthestaticanddynamicload,itpresentsspecialproblemstothebridgedesignerbecauseofthevibrationandimpactstressescreatedbymovingvehicles.雖然隨時在橋面上移動的車輛的總重量相對于靜荷載和動荷載來說是一個很少的部分，而對設(shè)計者來說，因為機動車輛產(chǎn)生的振動和沖擊壓力而會出現(xiàn)特殊問題。Forexample,thesevereimpactscausedbyirregularitiesofvehiclemotionorbumpsintheroadwaymaymomentarilydoubletheeffectoftheliveloadonthebridge.例如：在路面上機動車的不規(guī)則的運動或碰撞對橋面產(chǎn)生瞬時雙倍活荷載的作用力。,Windexertsforceonabridgebothdirectlybystrikingthebridgestructureandindirectlybystrikingvehiclesthatarecrossingthebridge.風(fēng)在橋上的作用的力包括：直接作用橋結(jié)構(gòu)的力和間接的通過作用在通行車輛的力。Ifthewindinducesaeroelasticvibration,asinthecaseoftheTacomaNarrowsBridge,itseffectmaybegreatlyamplified.如果出現(xiàn)空氣彈性振動，在這種情況下的TacomaNarrows大橋的風(fēng)作用被大大地增大，Becauseofthisdanger,thebridgedesignermakesprovisionsforthestrongestwindsthatmayoccuratthebridgelocation.provisionn.供應(yīng),提供,供給，準(zhǔn)備,防備；食物和飲料規(guī)定,條款,條件由于這種危險的存在，橋的設(shè)計者必須知道橋址處可能發(fā)生的最大的風(fēng)。Otherforcesthatmayactonthebridge,suchasstressescreatedbyearthquaketremors,mustalsobeprovidedfor.還有其它的力作用在橋上，如：地震產(chǎn)生的壓力也必須注意。,Specialattentionmustoftenbegiventothedesignofthebridgepiers,sinceheavyloadsmaybeimposedonthembycurrents,waves,andfloatingiceanddebris.Occasionallyapiermayevenbehitbyapassinghip.對橋墩的設(shè)計要給予特殊的關(guān)注，因為橋墩承擔(dān)水流，浮冰和漂浮物而產(chǎn)生的重荷載，橋墩通常還有被船撞擊的可能。,Electroniccomputersareplayinganeverincreasingroleinassistingbridgedesignersintheanalysisofforces.電腦在力分析上協(xié)助橋梁設(shè)計者，起著很重要的作用。Theuseofprecisemodeltesting,particularlyforstudyingthedynamicbehaviorofbridges,alsohelpsdesigners.用一個精確的模型試驗，尤其對橋的動力的活動狀態(tài)的研究也可以幫助設(shè)計者。Ascaled-downmodelofthebridgeisconstructed,andvariousgaugestomeasurestrains,accelerations,anddeformationsareplacedonthemodel.一個縮尺比例的橋模結(jié)構(gòu)中，布置很多位移計對橋模各處的應(yīng)力，加速度和變形進行測量。,Themodelbridgeisthensubjectedtovariousscaled-downloadordynamicconditiontofindoutwhatwillhappen.橋模在同樣比例的荷載和動力條件作用下，來分析橋的受力行為。WindtunneltestsmayalsobemadetoensurethatnothingliketheTacomaNarrowsBridgefailurecanoccur.Withmoderntechnologicalaids,thereismuchlesschanceofbridgefailurethaninthepast.風(fēng)洞試驗也可以確保不再發(fā)生TacomaNarrows大橋的失敗。在現(xiàn)代技術(shù)的幫助下，橋梁事故出現(xiàn)的機會將大大少于以前。,Constructionthefoundations.基礎(chǔ)施工Constructionstartswiththefoundation，whichmaycostalmostasmuchasthesuperstructure.施工都是從基礎(chǔ)開始的，基礎(chǔ)的花費幾乎大大超過上層建筑。Foundationsbuiltinwaterusuallypresentthegreatestdifficulties.Oneoftheoldermethods,whichisstillusedinshadowwaters,istoerectcofferdamssimilartotheringofcloselyspacedpilesthattheRomansused.水下基礎(chǔ)通常會遇到很大的困難，有個古老的方法常被用于淺水中，即在小范圍內(nèi)布置垂直圍堰而建橋墩。羅馬人常用這種方法。,Forconstructingfoundationsindeepwater,caissonshavelongbeenused.在深水中建基礎(chǔ)一般用沉箱法。thecaisson,whichisahugeboxclosedonallsidesexceptthebottom,isloweredontotheriverbed.沉箱是一個底部開口其余封閉的大盒子而沉入河床上，Workersinsidethecaisson,whichisfilledwithcompressedairtokeepoutthewater,digdeeperanddeeper,andthecaissonsinksasthediggingproceeds,Whenasuitabledepthisreached，thecaissonisfilledwithconcreteandbecomespartofthefoundationitself.工人們在為擋水而充滿壓縮空氣的沉箱里，越挖越深，沉箱也跟著下沉。當(dāng)達到合適的深度后在箱內(nèi)填入混泥土而成為基礎(chǔ)的一部分。,Anotherdeep-watermethod,lesshazardousandlesscostlythanthecaissonmethod,usessteelorconcretepiles.在深水中建基礎(chǔ)的另一種方法比沉箱法更安全和更低的成本，用于鋼或混泥土橋墩。Withmodernpiledrivers,longheavypilescanbedrivenevenIndeepwater.用現(xiàn)代的打樁機，長重樁可以打入深水中。Thepilescanbecutoffandcappedeitherabovethewaterlevelorbelowit.樁可以在水面或水下截斷或做成樁帽。Iftheyarecappedbelowthewaterlevel,aprefabricatedhollowpiercaseisfloatedouttothesite,sunkonthepiles,andthenfilledwithconcretetoformthepier.如在水下把它們做成樁帽，可把一個預(yù)制空心橋墩浮運到場地內(nèi)并沉入到樁上，然后灌入混泥土形成橋墩。,Erectingthesuperstructure.建造上部結(jié)構(gòu)Afterallpiersandabutmentsareinplace,theerectionofthesuperstructurebegins當(dāng)所有的樁和支柱建好后，則上部結(jié)構(gòu)開始建造。Themethodofconstructionuseddependslargelyonthetypeofbridgebeingbuilt.Therearesixconstructionmethods:falsework,flotation,cantilevering，sliding,directlifting,andSuspension.結(jié)構(gòu)的施工方法有很多種類，共有六類施工方法：腳手架、浮運、懸臂、滑移、直升和懸掛法。,Infalsworkconstruction,mainlyusedinbuildingconcretearchbridges,metalorwoodsupportsarebuilttemporarilytosupporttheerection.在用腳手架施工時，主要用來建混泥土拱橋，金屬或木支撐都是臨時搭設(shè)為支撐上部結(jié)構(gòu)。Agreatdealofingenuityisoftenrequiredjusttoerectthefalsework,especiallyforstructuresoverswiftriversordeepcanyons.Temporarypilesandtrestlesarecommonlyusedinwideshallowrivers.Trestle腳手架,高架橋,三角凳腳手架都是根據(jù)需要而靈活搭建的，尤其結(jié)構(gòu)在激流河流或深谷上時，臨時橋墩和架子一般在寬而淺的河上使用。,Inthefloatationmethod,mainlyusedinbuildinglongbridges,largebridgesectionareprefabricatedonshoreandfloatedoutonbargestothebridgesite.浮運法主要用來施工很長的橋梁，主橋部分是在河岸預(yù)制的，然后用駁船浮移到橋梁位置。Thesectionsarethenhoistedintoplace,eitherbyfloatingderricksorbywinchesplacedonpreviouslyconstructedsectionsofthebridge.浮吊起重機或卷揚機安裝在已建成橋的部位，然后把預(yù)知的主橋部分精確吊到大橋的施工部位。,Thecantileveringtechniqueisusednotonlyforcantileverbridgesbutalsoforsteelarchbridges.懸臂技術(shù)不僅用于懸臂橋中，也用于剛拱橋上，Constructionstartsatanabutmentandextendstowardthecenterpiecebypiece.Movingderricksandcranesonthecompletedportionofthestructurehandletheheavymaterial.施工時先建成一個橋臺，然后一步步延伸到中央，在已建好的結(jié)構(gòu)部分的起重機和吊車，來回移動完成施工材料的運輸。,Slidingconstructionisusedonlyrarely.Inthismethod,aprefabricatedunit,suchasatruss,iserectedonshoreandslidoutoveratemporaryorpermanentsupportuntilitcomestorestonanotherSupport.滑移法在施工中很少用到。這種方法，如一個預(yù)制構(gòu)件，如桁架結(jié)構(gòu)，豎立在河岸上，然后在臨時或永久性的支撐滑動，直到它進入安裝的另一個支撐上。Inthedirectliftingmethod,mainlyusedforlight，short-spanhighwaybridge,aprefabricatedbridgeunitisliftedbyahoistandswungdirectlyontothebridgesupports.直升法主要用于輕質(zhì)小跨度的公路橋。每一個預(yù)制橋單元被垂直懸起并旋轉(zhuǎn)到橋梁支撐點上。,Intheconstructionofsuspensionbridges,thecablesarestrungbetweenthebridgetowersandusedasasupportforthebridgedeck.在由懸索橋的施工中，一串纜繩連接到兩側(cè)的橋塔上，被用作橋面支撐點。Thedeckerectionstartsattheendsofthebridgeandprogressestowardthecenter.Atravelingderrick,movingonthecompletedpartofthedeck,isusedtohandleheavymaterial.橋面施工從橋的兩端開始，向中間進行，在已完成的橋面上移動，用來運送重材。Temporarysuspensioncablesareoccasionallyusedintheconstructionofothertypeofbridgestoconveymaterialacrossthespan.懸掛鋼纜，有時在其他類型的橋梁中被用來運輸材料。,Inallmethodsofconstruction,itisnecessarytodeterminethestressesanddeformationateverystageofconstruction.Stressesinapartlycompletedbridge-constructedbythecantilevermethod-canexceedthestressesinacompletedbridgebecauseofthetotallydifferentconditionsofsupportandloading.所有的施工方法中，都需要驗算施工階段的應(yīng)力和變形，在用懸臂梁法施工的橋梁中，因為完全不同的支撐和荷載條件，未竣工橋梁內(nèi)的應(yīng)力可能會超過已竣工橋梁內(nèi)的應(yīng)力。Whentheroadwayissurfaced,andsigns,lighting,guardrails,andotheraccessoriesareinstalled,thebridgeisreadyforuse.當(dāng)公路的鋪裝，標(biāo)志，燈光，護欄和附屬設(shè)施完成后，橋梁就準(zhǔn)備投入使用了。,