土木工程專業(yè)英語武漢理工大學(xué)出版社l.ppt

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8BridgeDesignandConstruction橋的設(shè)計(jì)與建造,1.Newwordsanalysisaccessory=access(increased)oryDerrick=fromDerrick,thesurnameofaLondonhangmanDebris=orignearly18thcent.:fromFrenchdbris,fromobsoletedbriser‘breakdown’,Planning.Thefirststepleadingtotheconstructionofamodernmajorbridgeisacomprehensivestudytodeterminewhetherabridgeisneeded.規(guī)劃設(shè)計(jì)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(shí)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(duì)附近高速公路網(wǎng)交通堵塞的調(diào)劑，對(duì)當(dāng)?shù)亟?jīng)濟(jì)的影響和橋的造價(jià)等因素進(jìn)行評(píng)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(fèi)，依靠過通行費(fèi)來支付的發(fā)行債券的規(guī)模都要被考慮進(jìn)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(cè)量在確定場(chǎng)地時(shí)，現(xiàn)場(chǎng)測(cè)繪工作開始進(jìn)行，做好精確的實(shí)地測(cè)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(jìn)行。,Selectionofbridgedesign.橋梁設(shè)計(jì)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(diǎn)，如跨越河流；（2）目的，如建橋?yàn)榱朔奖憬煌?；?）跨度；（4）可用材料強(qiáng)度；（5）花費(fèi)；（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(jì)和最有效。如下表所示：,,Asindicatedinthetable,thereisaconsiderableoverlapintherangeofapplicabilityofthevarioustypes．Insomecases，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(shí)例中，在不同的初步設(shè)計(jì)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(jì)者能選用大量的現(xiàn)代高強(qiáng)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)(3，515kg／sqcm)anddoesnotneedtobepaintedbecauseanoxidecoatingformsonitssurfaceandinhibitscorrosion．inhibit抑制,約束,[化][醫(yī)]抑制拿Varian-Narrows大橋來說，設(shè)計(jì)者使用了七種不同的合金鋼，其中之一的合金的屈服強(qiáng)度為50000英鎊每平方英寸（3115kg/c㎡）,而且不需要油漆保護(hù)，因?yàn)橛幸环N氧化膜覆蓋在它的表面而防止腐蝕。Thedesigneralsocanselectsteelwiresforsuspensioncablesthathavetensilestrengthsupto250，000psi(17，577kg／sqcm)．設(shè)計(jì)者還選用鋼絲繩作為懸索，它的抗拉強(qiáng)度超過250000英鎊每平方英寸（17577kg/c㎡）,,Concretewithcompressivestrengthsashighas8,000psi(562．5kg／sqCm)cannowbeproducedforuseinbridges,anditcanbegivenhighdurabilityagainstchippingandweatheringbytheadditionofspecialchemicalagentsandcontrolofthehardeningprocess.chipping碎屑；小碎片weathering侵蝕,風(fēng)化現(xiàn)在，抗壓強(qiáng)度高達(dá)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(qiáng)的預(yù)應(yīng)力混凝土，其強(qiáng)度達(dá)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(qiáng)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(qiáng)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(dá)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(chǔ)備。Thecalculationoftheprecisenatureoftheindividualstressesandstrainsinthestructure,calledanalysis,isperhapsthemosttechnicallycomplexaspectofbridgebuilding.對(duì)結(jié)構(gòu)的各種應(yīng)力和應(yīng)變的準(zhǔn)確特性進(jìn)行計(jì)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(dòng)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(dòng)荷載或靜荷載有很多，包括橋面上的機(jī)動(dòng)車，風(fēng)荷載，和積冰積雪荷載。,Althoughofthetotalweightofthevehiclesmovingoverabridgeatanytimeisgenerallyasmallfractionofthestaticanddynamicload,itpresentsspecialproblemstothebridgedesignerbecauseofthevibrationandimpactstressescreatedbymovingvehicles.雖然隨時(shí)在橋面上移動(dòng)的車輛的總重量相對(duì)于靜荷載和動(dòng)荷載來說是一個(gè)很少的部分，而對(duì)設(shè)計(jì)者來說，因?yàn)闄C(jī)動(dòng)車輛產(chǎn)生的振動(dòng)和沖擊壓力而會(huì)出現(xiàn)特殊問題。Forexample,thesevereimpactscausedbyirregularitiesofvehiclemotionorbumpsintheroadwaymaymomentarilydoubletheeffectoftheliveloadonthebridge.例如：在路面上機(jī)動(dòng)車的不規(guī)則的運(yùn)動(dòng)或碰撞對(duì)橋面產(chǎn)生瞬時(shí)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(dòng)，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(xiǎn)的存在，橋的設(shè)計(jì)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(duì)橋墩的設(shè)計(jì)要給予特殊的關(guān)注，因?yàn)闃蚨粘袚?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(jì)者，起著很重要的作用。Theuseofprecisemodeltesting,particularlyforstudyingthedynamicbehaviorofbridges,alsohelpsdesigners.用一個(gè)精確的模型試驗(yàn)，尤其對(duì)橋的動(dòng)力的活動(dòng)狀態(tài)的研究也可以幫助設(shè)計(jì)者。Ascaled-downmodelofthebridgeisconstructed,andvariousgaugestomeasurestrains,accelerations,anddeformationsareplacedonthemodel.一個(gè)縮尺比例的橋模結(jié)構(gòu)中，布置很多位移計(jì)對(duì)橋模各處的應(yīng)力，加速度和變形進(jìn)行測(cè)量。,Themodelbridgeisthensubjectedtovariousscaled-downloadordynamicconditiontofindoutwhatwillhappen.橋模在同樣比例的荷載和動(dòng)力條件作用下，來分析橋的受力行為。WindtunneltestsmayalsobemadetoensurethatnothingliketheTacomaNarrowsBridgefailurecanoccur.Withmoderntechnologicalaids,thereismuchlesschanceofbridgefailurethaninthepast.風(fēng)洞試驗(yàn)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(jī)會(huì)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(fèi)幾乎大大超過上層建筑。Foundationsbuiltinwaterusuallypresentthegreatestdifficulties.Oneoftheoldermethods,whichisstillusedinshadowwaters,istoerectcofferdamssimilartotheringofcloselyspacedpilesthattheRomansused.水下基礎(chǔ)通常會(huì)遇到很大的困難，有個(gè)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(gè)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?cè)跒閾跛錆M壓縮空氣的沉箱里，越挖越深，沉箱也跟著下沉。當(dāng)達(dá)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(jī)，長重樁可以打入深水中。Thepilescanbecutoffandcappedeitherabovethewaterlevelorbelowit.樁可以在水面或水下截?cái)嗷蜃龀蓸睹?。Iftheyarecappedbelowthewaterlevel,aprefabricatedhollowpiercaseisfloatedouttothesite,sunkonthepiles,andthenfilledwithconcretetoformthepier.如在水下把它們做成樁帽，可把一個(gè)預(yù)制空心橋墩浮運(yùn)到場(chǎng)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(yùn)、懸臂、滑移、直升和懸掛法。,Infalsworkconstruction,mainlyusedinbuildingconcretearchbridges,metalorwoodsupportsarebuilttemporarilytosupporttheerection.在用腳手架施工時(shí)，主要用來建混泥土拱橋，金屬或木支撐都是臨時(shí)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(shí)，臨時(shí)橋墩和架子一般在寬而淺的河上使用。,Inthefloatationmethod,mainlyusedinbuildinglongbridges,largebridgesectionareprefabricatedonshoreandfloatedoutonbargestothebridgesite.浮運(yùn)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(jī)或卷揚(yáng)機(jī)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(shí)先建成一個(gè)橋臺(tái)，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(jī)和吊車，來回移動(dòng)完成施工材料的運(yùn)輸。,Slidingconstructionisusedonlyrarely.Inthismethod,aprefabricatedunit,suchasatruss,iserectedonshoreandslidoutoveratemporaryorpermanentsupportuntilitcomestorestonanotherSupport.滑移法在施工中很少用到。這種方法，如一個(gè)預(yù)制構(gòu)件，如桁架結(jié)構(gòu)，豎立在河岸上，然后在臨時(shí)或永久性的支撐滑動(dòng)，直到它進(jìn)入安裝的另一個(gè)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(gè)預(yù)制橋單元被垂直懸起并旋轉(zhuǎn)到橋梁支撐點(diǎn)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(diǎn)。Thedeckerectionstartsattheendsofthebridgeandprogressestowardthecenter.Atravelingderrick,movingonthecompletedpartofthedeck,isusedtohandleheavymaterial.橋面施工從橋的兩端開始，向中間進(jìn)行，在已完成的橋面上移動(dòng)，用來運(yùn)送重材。Temporarysuspensioncablesareoccasionallyusedintheconstructionofothertypeofbridgestoconveymaterialacrossthespan.懸掛鋼纜，有時(shí)在其他類型的橋梁中被用來運(yùn)輸材料。,Inallmethodsofconstruction,itisnecessarytodeterminethestressesanddeformationateverystageofconstruction.Stressesinapartlycompletedbridge-constructedbythecantilevermethod-canexceedthestressesinacompletedbridgebecauseofthetotallydifferentconditionsofsupportandloading.所有的施工方法中，都需要驗(yàn)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?yàn)橥耆煌闹魏秃奢d條件，未竣工橋梁內(nèi)的應(yīng)力可能會(huì)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(hù)欄和附屬設(shè)施完成后，橋梁就準(zhǔn)備投入使用了。,,