橋梁畢業(yè)設(shè)計外文翻譯

外文資料TheTenthEastAsia-PacificConferenceonStructuralEngineeringandConstructionAugust3-5,2006,BangkokStructuralRehabilitationofConcreteBridgeswithCFRPComposites-PracticalDetailsandApplicationsRiyadS.ABOUTAHA1,andNuttawatCHUTARAT2ABSTRACT:Manyoldexistingbridgesarestillactiveinthevarioushighwaytransportationnetworks,carryingheavierandfastertrucks,inallkindsofenvironments.Water,salt,andwindhavecauseddamagetotheseoldbridges,andscarcityofmaintenancefundshasaggravatedtheirconditions.Oneattempttorestoretheoriginalcondition;andtoextendtheservicelifeofconcretebridgesisbytheuseofcarbonfiberreinforcedpolymer(CFRP)composites.ThereappeartobeverylimitedguidesonrepairofdeterioratedconcretebridgeswithCFRPcomposites.Inthispaper,guidelinesfornondestructiveevaluation(NDE),nondestructivetesting(NDT),andrehabilitationofdeterioratedconcretebridgeswithCFRPcompositesarepresented.TheeffectofdetailingonductilityandbehaviorofCFRPstrengthenedconcretebridgesarealsodiscussedandpresented.KEYWORDS:Concretedeterioration,corrosionofsteel,bridgerehabilitation,CFRPcomposites.1IntroductionThereareseveraldestructiveexternalenvironmentalfactorsthatlimittheservicelifeofbridges.Thesefactorsincludebutnotlimitedtochemicalattacks,corrosionofreinforcingsteelbars,carbonationofconcrete,andchemicalreactionofaggregate.Ifbridgeswerenotwellmaintained,thesefactorsmayleadtoastructuraldeficiency,whichreducesthemarginofsafety,andmayresultinstructuralfailure.Inordertorehabilitateand/orstrengthendeterioratedexistingbridges,thoroughevaluationshouldbeconducted.Thepurposeoftheevaluationistoassesstheactualconditionofanyexistingbridge,andgenerallytoexaminetheremainingstrengthandloadcarrycapacityofthebridge.1AssociateProfessor,SyracuseUniversity2Lecturer,SripatumUniversity,Oneattempttorestoretheoriginalcondition,andtoextendtheservicelifeofconcretebridgesisbytheuseofcarbonfiberreinforcedpolymer(CFRP)composites.InNorthAmerica,EuropeandJapan,CFRPhasbeenextensivelyinvestigatedandapplied.SeveraldesignguideshavebeendevelopedforstrengtheningofconcretebridgeswithCFRPcomposites.However,thereappeartobeverylimitedguidesonrepairofdeterioratedconcretebridgeswithCFRPcomposites.Thispaperpresentsguidelinesforrepairofdeterioratedconcretebridges,alongwithproperdetailing.Evaluation,nondestructivetesting,andrehabilitationofdeterioratedconcretebridgeswithCFRPcompositesarepresented.SuccessfulapplicationofCFRPcompositesrequiresgooddetailingastheforcesdevelopedintheCFRPsheetsaretransferredbybondattheconcrete-CFRPinterface.TheeffectofdetailingonductilityandbehaviorofCFRPstrengthenedconcretebridgeswillalsobediscussedandpresented.2DeterioratedConcreteBridgesDurabilityofbridgesisofmajorconcern.Increasingnumberofbridgesareexperiencingsignificantamountsofdeteriorationpriortoreachingtheirdesignservicelife.Thisprematuredeteriorationconsideredaproblemintermsofthestructuralintegrityandsafetyofthebridge.Inaddition,deteriorationofabridgehasaconsiderablemagnitudeofcostsassociatedwithit.Inmanycases,therootofadeteriorationproblemiscausedbycorrosionofsteelreinforcementinconcretestructures.Concretenormallyactstoprovideahighdegreeofprotectionagainstcorrosionoftheembeddedreinforcement.However,corrosionwillresultinthosecasesthattypicallyexperiencepoorconcretequality,inadequatedesignorconstruction,andharshenvironmentalconditions.Ifnottreatedadurabilityproblem,e.g.corrosion,mayturnintoastrengthproblemleadingtoastructuraldeficiency,asshowninFigure1.Figure1Corrosionofthesteelbarsisleadingtoastructuraldeficiency3Non-destructiveTestingofDeterioratedConcreteInordertodesignasuccessfulretrofitsystem,theconditionoftheexistingbridgeshouldbethoroughlyevaluated.Evaluationofexistingbridgeelementsorsystemsinvolvesreviewoftheasbuiltdrawings,aswellasaccurateestimateoftheconditionoftheexistingbridge,asshowninFigure2.Dependingonthepurposeofevaluation,non-destructivetestsmayinvolveestimationofstrength,saltcontents,corrosionrates,alkalinityinconcrete,etc.Figure2VisibleconcretedistressmarkedonanelevationofaconcretebridgepierAlthoughmostofthenon-destructivetestsdonotcauseanydamagetoexistingbridges,someNDTmaycauseminorlocaldamage(e.g.drilledholes&coring)thatshouldberepairedrightaftertheNDT.Thesetestsarealsoreferredtoaspartialdestructivetestsbutfallundernon-destructivetesting.Inordertoselectthemostappropriatenon-destructivetestforaparticularcase,thepurposeofthetestshouldbeidentified.Ingeneral,therearethreetypesofNDTtoinvestigate:(1)strength,(2)otherstructuralproperties,and(3)qualityanddurability.Thestrengthmethodsmayinclude;compressivetest(e.g.coretest/reboundhammer/ultrasonicpulsevelocity),surfacehardnesstest(e.g.reboundhammer),penetrationtest(e.g.Windsorprobe),andpullouttest(anchortest).Otherstructuraltestmethodsmayinclude;concretecoverthickness(cover-meter),locatingrebars(rebarlocator),rebarsize(somerebarlocators/rebardatascan),concretemoisture(acquameter/moisturemeter),cracking(visualtest/impactecho/ultrasonicpulsevelocity),delamination(hammertest/ultrasonicpulsevelocity/impactecho),flawsandinternalcracking(ultrasonicpulsevelocity/impactecho),dynamicmodulusofelasticity(ultrasonicpulsevelocity),Possion’sratio(ultrasonicpulsevelocity),thicknessofconcreteslaborwall(ultrasonicpulsevelocity),CFRPdebonding(hammertest/infraredthermographictechnique),andstainonconcretesurface(visualinspection).Qualityanddurabilitytestmethodsmayinclude;rebarcorrosionrate–fieldtest,chlorideprofilefieldtest,rebarcorrosionanalysis,rebarresistivitytest,alkali-silicareactivityfieldtest,concretealkalinitytest(carbonationfieldtest),concretepermeability(fieldtestforpermeability).4Non-destructiveEvaluationofDeterioratedConcreteTheprocessofevaluatingthestructuralconditionofanexistingconcretebridgeconsistsofcollectinginformation,e.g.drawingsandconstruction&inspectionrecords,analyzingNDTdata,andstructuralanalysisofthebridge.Theevaluationprocesscanbesummarizedasfollows:(1)Planningfortheassessment,(2)Preliminaryassessment,whichinvolvesexaminationofavailabledocuments,siteinspection,materialsassessment,andpreliminaryanalysis,(3)Preliminaryevaluation,thisinvolves:examinationphase,andjudgmentalphase,andfinally(4)thecost-impactstudy.Iftheinformationisinsufficienttoconductevaluationtoaspecificrequiredlevel,thenadetailedevaluationmaybeconductedfollowingsimilarstepsfortheabove-mentionedpreliminaryassessment,butin-depthassessment.Successfulanalyticalevaluationofanexistingdeterioratedconcretebridgeshouldconsidertheactualconditionofthebridgeandlevelofdeteriorationofvariouselements.Factors,e.g.actualconcretestrength,levelofdamage/deterioration,actualsizeofcorrodedrebars,lossofbondbetweensteelandconcrete,etc.shouldbemodeledintoadetailedanalysis.Ifsuchdetailedanalysisisdifficulttoaccomplishwithinareasonableperiodoftime,thenevaluationbyfieldloadtestingoftheactualbridgeinquestionmayberequired.5BridgeRehabilitationwithCFRPCompositesApplicationofCFRPcompositematerialsisbecomingincreasinglyattractivetoextendtheservicelifeofexistingconcretebridges.ThetechnologyofstrengtheningexistingbridgeswithexternallybondedCFRPcompositeswasdevelopedprimarilyinJapan(FRPsheets),andEurope(laminates).Theuseofthesematerialsforstrengtheningexistingconcretebridgesstartedinthe1980s,firstasasubstitutetobondedsteelplates,andthenasasubstituteforsteeljacketsforseismicretrofitofbridgecolumns.CFRPCompositematerialsarecomposedoffiberreinforcementbondedtogetherwitharesinmatrix.Thefibersprovidethecompositewithitsuniquestructuralproperties.Theresinmatrixsupportsthefibers,protectthem,andtransfertheappliedloadtothefibersthroughshearingstresses.MostofthecommerciallyavailableCFRPsystemsintheconstructionmarketconsistofuniaxialfibersembeddedinaresinmatrix,typicallyepoxy.Carbonfibershavelimitedultimatestrain,whichmaylimitthedeformabilityofstrengthenedmembers.However,undertrafficloads,localdebondingbetweenFRPsheetsandconcretesubstratewouldallowforacceptablelevelofglobaldeformationsbeforefailure.CFRPcompositescouldbeusedtoincreasetheflexuralandshearstrengthofbridgegirdersincludingpiercapbeams,asshowninFigure3.InordertoincreasetheductilityofCFRPstrengthenedconcretegirders,thelongitudinalCFRPcompositesheetsusedforflexuralstrengtheningshouldbeanchoredwithtransverse/diagonalCFRPanchorstopreventprematuredelaminationofthelongitudinalsheetsduetolocalizeddebondingattheconcretesurface-CFRPsheetinterface.InordertopreventstressconcentrationandprematurefractureoftheCFRPsheetsatthecornersofconcretemembers,thecornersshouldberoundedat50mm(2.0inch)radius,asshowninFigure3.Deteriorationofconcretebridgemembersduetocorrosionofsteelbarsusuallyleadsinlossofsteelsectionanddelaminationofconcretecover.Asaresult,suchdeteriorationmayleadtostructuraldeficiencythatrequiresimmediateattention.Figure4showsrehabilitationofstructurallydeficientconcretebridgepierusingCFRPcomposites.Figure3FlexuralandshearstrengtheningofconcretebridgepierwithFRPcompositesFigure4RehabilitationofdeterioratedconcretebridgepierwithCFRPcomposites6SummaryandConclusionsEvaluation,non-destructivetestingandrehabilitationofdeterioratedconcretebridgeswerepresented.Deteriorationofconcretebridgecomponentsduetocorrosionmayleadtostructuraldeficiencies,e.g.flexuraland/orshearfailures.ApplicationofCFRPcompositematerialsisbecomingincreasinglyattractivesolutiontoextendtheservicelifeofexistingconcretebridges.CFRPcompositescouldbeutilizedforflexuralandshearstrengthening,aswellasforrestorationofdeterioratedconcretebridgecomponents.TheCFRPcompositesheetsshouldbewelldetailedtopreventstressconcentrationandprematurefractureordelamination.Forsuccessfulrehabilitationofconcretebridgesincorrosiveenvironments,acorrosionprotectionsystemshouldbeusedalongwiththeCFRPsystem.第十屆東亞太結(jié)構(gòu)工程設(shè)計與施工會議2006年8月3-5號，曼谷，泰國碳纖維復合材料修復混凝土橋梁結(jié)構(gòu)的詳述及應用RiyadS.ABOUTAHA1,andNuttawatCHUTARAT2摘要：在各式各樣的公路交通網(wǎng)絡(luò)中，許多現(xiàn)有的古老橋梁，在各種惡劣的環(huán)境下，如更重的荷載和更快的車輛等條件下，依然在被使用著。沖刷、腐蝕和風化對這些古老的橋梁已經(jīng)造成了破壞，而維修資金短缺更加劇了它們的損壞。一個利用碳纖維增強復合材料〔CFRP〕來延長混凝土橋梁的使用壽命的想法使橋梁恢復了原有的狀態(tài)。然而，采用碳纖維復合材料修復受損混凝土橋梁的指導和標準還非常有限。在本文中對無損探傷、無損檢測和利用碳纖維復合材料修復已遭侵蝕的橋梁的方法進行了介紹。此設(shè)計對碳纖維增強混凝土橋的延性，及其應用后效果也進行了討論和介紹。關(guān)鍵詞:混凝土腐蝕，鋼筋銹蝕，橋梁修復，碳纖維復合材料1簡介在這里存在幾個有害的外部環(huán)境因素影響著橋梁的耐久性。這些因素包括但又不僅限于化學物的侵蝕，受力鋼筋的銹蝕，混凝土的碳化，化學物質(zhì)的聚合反響。如果橋梁維護不好，這些因素可能導致結(jié)構(gòu)的受損，如結(jié)構(gòu)邊緣不穩(wěn)定或結(jié)構(gòu)損毀。為了修復日漸惡化的現(xiàn)存橋梁，應當對其作徹底的評估。目的是通過大致檢測剩余耐久度和承載力，評定出所有現(xiàn)存橋梁的真實情況。應用碳纖維復合材料可以恢復混凝土橋梁最初的狀況并延長其使用年限。在北美、歐洲和日本，碳纖維復合材料應經(jīng)得到深入的研究和廣泛的應用。碳纖維復合材料的幾個設(shè)計指南也已經(jīng)被應用于強化混凝土橋梁。然而，采用碳纖維復合材料修復損壞的混凝土橋梁的指導和標準還非常有限。本文通過適宜的例子給出了修復受損混凝土梁橋的準那么，列出了評估、無損檢測、碳纖維復合材料復原受損混凝土橋梁。碳纖維復合材料的成功應用由于良好的細節(jié)設(shè)計，它主要考慮了集中力在碳纖維復合材料中依靠混凝土與碳纖維復合材料接觸面間的粘合劑轉(zhuǎn)移。此設(shè)計對碳纖維增強混凝土橋的延性和反響的效果也進行了討論和介紹。2混凝土橋梁的損壞橋梁的使用年限應該給予極大地關(guān)注。越來越多的橋梁在到達設(shè)計使用年限之前出現(xiàn)令人側(cè)目的破損。這些過早出現(xiàn)的損壞使得橋梁的結(jié)構(gòu)可靠性和平安性成為1副教授，雪城大學，美國2講師，斯巴頓大學，泰國了值得考慮的問題?？偟膩碚f，橋梁的損壞與考慮它的花費多少是緊密相關(guān)的。在很多情況下，損壞問題的根源是混凝土結(jié)構(gòu)中受力鋼筋的腐蝕。通常由混凝土保護層預防受力筋的腐蝕。然而，這些具有代表性的問題，如混凝土質(zhì)量差、不適當?shù)脑O(shè)計或施工和周圍惡劣的環(huán)境導致了鋼筋的腐蝕。如果不及時處理像鋼筋腐蝕這種耐久性問題，可能會引起受力不均問題，進而導致結(jié)構(gòu)失穩(wěn)，如圖1所示。圖1鋼筋的銹蝕導致的結(jié)構(gòu)失穩(wěn)3損壞的混凝土梁橋墩柱的無損檢測為了設(shè)計一個成功的新式系統(tǒng)，應該對橋梁現(xiàn)有的情況作徹底評估。評價現(xiàn)有橋梁的元素或體系需要翻看asbuilt圖紙，才能準確的評估出現(xiàn)有橋梁的狀況，如圖2所示。根據(jù)評估的目的，無損測試應該包括的內(nèi)容：強度的檢測，鹽度，腐蝕率，混凝土中堿含量等等。雖然大多數(shù)的無損測試對現(xiàn)有橋梁不會造成任何損壞，一些無損檢測可能導致的輕微局部損傷〔如鉆洞取芯〕，在無損檢測完畢后應予以修復。這些測試也被叫作局部破壞性測試,但屬于無損檢測。裸露的鋼筋裸露的鋼筋裂縫平行于銹蝕的鋼筋剝離〔敲擊有空心聲音〕彎剪/剪切裂縫圖2混凝土橋墩可見缺陷正面圖為了針對特殊情況選擇最適宜的無損檢測，應該明確測試的目的。一般來說,有三種類型的無損檢測進行調(diào)查：〔1〕強度；〔2〕其他結(jié)構(gòu)性質(zhì)；〔3〕質(zhì)量及耐久性。強度測試的方法可能包括：抗壓測試〔如軸心抗壓、反彈測試儀、超聲波脈沖速度檢測〕；外表硬度測試〔如反彈儀測試〕；貫入度試驗〔如溫莎探針〕；拉拔試驗〔錨索抗拔試驗〕。其它結(jié)構(gòu)測試方法還包括：混凝土保護層厚度〔保護層測量〕；定位鋼筋位置〔鋼筋定位器〕；鋼筋尺寸〔某些鋼筋定位器、鋼筋數(shù)據(jù)掃描儀〕；混凝土的濕度〔含水量測試儀、水分測定儀〕；混凝土裂縫檢查〔外觀鑒定、回音法、超聲波脈沖回波速度檢查法〕；混凝土分層剝離〔錘擊試驗、超聲波脈沖回波速度檢查法、回音法〕；缺陷和內(nèi)部開裂〔超聲波脈沖回波速度檢查法、回音法〕；動態(tài)彈性模量〔超聲波脈沖回波速度檢查法〕；泊松比〔超聲波脈沖回波速度檢查法〕；混凝土板或墻的厚度〔超聲波脈沖回波速度檢查法〕；碳纖維復合材料剝離〔錘擊