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1、外文资料TheTenthEastAsia-PacificConferenceonStructuralEnghieerhigandConstructionAugust3-5f2006,Bangkok,ThailandStructuralRehabilitationofConcreteBridgeswithCFRpcomposites-PracticalDetailsandApplicationsRiyadS.ABOUTAHA1,andNuttawatCHUTARAT2ABSTRACT:Manyoldexistingbridgesarestillactiveinthevarioushighwayt
2、ransportationnetworks,carryingheavierandfastertrucks,inallkindsofenvironments.Water,salt,andwindhavecauseddamagetotheseoldbridges,andscarcityofmaintenancefundsHasaggravatedtheirconditions.Oneattempttorestoretheoriginalcondition;andtoextendtheservicelifeofconcretebridgesisbytheuseofcarbonfiberreinfor
3、cedpolymer(CFRP)Composites.ThereappeartobeverylimitedguidesonrepairofdeterioratedconcretebridgeswithCFRPcomposites.Inthispaper,guidelinesfornondestructiveevaluation(NDE),nondestructivetesting(NDT),andrehabilitationofdeterioratedconcretebridgeswithCFRPcompositesarepresented.Theeffectofdetailingonduct
4、ilityandbehaviorofCFRPstrengthenedconcretebridgesarealsodiscussedandpresented.KEYWORDS:Concretedeterioration,corrosionofsteel,bridgerehabilitation,CFRPcomposites.!IntroductionThereareseveraldestructiveexternalenvironmentalfactorsthatlimittheservicelifeofbridges.Thesefactorsincludebutnotlimitedtochem
5、icalattacks,corrosionofreinforcingsteelbars,carbonationofconcrete,andchemicalreactionofaggregate.Ifbridgeswerenotwellmaintained,Ihesefactorsmayleadtoastructuraldeficiency,whichreducesthemarginofsafety,andmayresultinstructuralfailure.Inordertorehabilitateand/orstrengthendeterioratedexistingbridges,th
6、oroughevaluationshouldbeconducted.Thepurposeoftheevaluationistoassesstheactualconditionofanyexistingbridge,andgenerallytoexaminetheremainingstrengthandloadcarrycapacityofthebridge.7AssociateProfessor,SyracuseUniversity,U.S,A.2Lecturer,SripatumUniversity,Thailand.Oneattempttorestoretheoriginalconditi
7、on,andtoextendtheservicelifeofconcretebridgesisbytheuseofcarbonfiberreinforcedpolymer(CFRP)composites.InNorthAmerica,EuropeandJapan,CFRPhasbeenextensivelyinvestigatedandapplied.SeveraldesignguideshavebeendevelopedforstrengtheningofconcretebridgeswithCFRPcomposites.However,thereappeartobeverylimitedg
8、uidesonrepairofdeterioratedconcretebridgeswithCFRPcomposites.Thispaperpresentsguidelinesforrepairofdeterioratedconcretebridges,alongwithproperdetailing.Evaluation,nondestructivetesting,andrehabilitationofdeterioratedconcretebridgeswithCFRPcompositesarepresented.SuccessfulapplicationofCFRPcompositesr
9、equiresgooddetailingastheforcesdevelopedintheCFRPsheetsaretransferredbybondattheconcrete-CFRPinterface.TheeffectofdetailingOnductilityandbehaviorofCFRPstrengthenedconcretebridgeswillalsobediscussedandpresented.2DeterioratedConcreteBridgesDurabilityofbridgesisofmajorconcern.Increasingnumberofbridgesa
10、reexperiencingsignificantamountsofdeteriorationpriortoreachingtheirdesignservicelife.Thisprematuredeteriorationconsideredaproblemintermsofthestructuralintegrityandsafetyofthebridge.Inaddition,deteriorationofabridgehasaconsiderablemagnitudeofcostsassociatedwithit.Inmanycases,therootofadeteriorationpr
11、oblemiscausedbycorrosionofsteelreinforcementinconcreteStructures.Concretenormallyactstoprovideahighdegreeofprotectionagainstcorrosionoftheembeddedreinfbrcement.However,corrosionwillresultinthosecasesthattypicallyexperiencepoorconcretequality,inadequatedesignorconstruction,andharshenvironmentalcondit
12、ions.Ifnottreatedadurabilityproblem,e.g.corrosion,mayturnintoastrengthproblemleadingtoastructuraldeficiency,asshowninFigurel.FigurelCorrosionofthesteelbarsisleadingtoastructuraldeficiency3Non-destructiveTestingofDeterioratedConcreteBridgePiersInordertodesignasuccessfulretrofitsystem,theconditionofth
13、eexistingbridgeshouldbethoroughlyevaluated.Evaluationofexistingbridgeelementsorsystemsinvolvesreviewoftheasbuiltdrawings,aswellasaccurateestimateoftheconditionoftheexistingbridge,asshowninFigure2.Dependingonthepurposeofevaluation,non-destructivetestsmayinvolveestimationofstrength,saltcontents,corros
14、ionrates,alkalinityinconcrete,etc.Figure2VisibleconcretedistressmarkedonanelevationofaconcretebridgepierAlthoughmostofthenon-destructivetestsdonotcauseanydamagetoexistingbridges,someNDTmaycauseminorlocaldamage(e.g.drilledholes&coring)thatshouldberepairedrightaftertheNDT.Thesetestsarealsoreferredtoas
15、partialdestructivetestsbutfallundernon-destructivetesting.Inordertoselectthemostappropriatenon-destructivetestforaparticularcase,thepurposeofthetestshouldbeidentified.Ingeneral,therearethreetypesofNDTtoinvestigate:(1)strength,(2)Otherstructuralproperties,and(3)qualityanddurability.Thestrengthmethods
16、mayinclude;Compressivetest(e.g.coretest/reboundhammer/ultrasonicpulsevelocity),surfacehardnesstest(e.g.reboundhammer),penetrationtest(e.g.Windsorprobe),andpullouttest(anchortest).Otherstructuraltestmethodsmayinclude;concretecoverthickness(cover-meter),locatingrebars(rebarlocator),rebarsize(somerebar
17、locators/rebardatascan),concretemoisture(acquametermoisturemeter),cracking(visualtest/impactecho/ultrasonicpulsevelocity),delamination(hammertest/ultrasonicpulsevelocity/impactecho),flawsandinternalcracking(ultrasonicpulsevelocity/impactecho),dynamicmodulusofelasticity(ultrasonicpulsevelocity),Possi
18、on,sratio(ultrasonicpulsevelocity),thicknessofconcreteslaborwall(ultrasonicpulsevelocity),CFRPdebonding(hammertest/infraredthermographictechnique),andstainonconcretesurface(visualinspection).Qualityanddurabilitytestmethodsmayinclude;rebarcorrosionrate-fieldtest,chlorideprofilefieldtest,rebarcorrosio
19、nanalysis,rebarresistivitytest,alkali-silicareactivityfieldtest,concretealkalinitytest(carbonationfieldtest),concretepermeability(fieldtestforpermeability).4Non-destructiveEvaluationofDeterioratedConcreteBridgePiersTheprocessofevaluatingthestructuralconditionofanexistingconcretebridgeconsistsofcolle
20、ctinginformation,e.g.drawingsandconstruction&inspectionrecords,analyzingNDTdata,andStructuralanalysisofthebridge.Theevaluationprocesscanbesummarizedasfollows:(1)Planningfortheassessment,(2)Preliminaryassessment,whichinvolvesexaminationofavailabledocuments,siteinspection,materialsassessment,andprelim
21、inaryanalysis,(3)Preliminaryevaluation,thisinvolves:examinationphase,andjudgmentalphase,andfinally(4)thecost-impactstudy.Iftheinformationisinsufficienttoconductevaluationtoaspecificrequiredlevel,thenadetailedevaluationmaybeconductedfollowingsimilarstepsfortheabove-mentionedpreliminaryassessment,buti
22、n-depthassessment.Successfulanalyticalevaluationofanexistingdeterioratedconcretebridgeshouldconsidertheactualconditionofthebridgeandlevelofdeteriorationofvariouselements.Factors,e.g.actualconcretestrength,levelofdamage/deterioration,actualsizeofcorrodedrebars,lossofbondbetweensteelandconcrete,etc.sh
23、ouldbemodeledintoadetailedanalysis.Ifsuchdetailedanalysisisdifficulttoaccomplishwithinareasonableperiodoftime,thenevaluationbyfieldloadtestingoftheactualbridgeinquestionmayberequired.SBridgeRehabilitationwithCFRPCompositesApplicationofCFRPcompositematerialsisbecomingincreasinglyattractivetoextendthe
24、serviceIifeofexistingconcretebridges.ThetechnologyofstrengtheningexistingbridgeswithexternallybondedCFRPcompositeswasdevelopedprimarilyinJapan(FRPsheets),andEurope(Iaminates),Theuseofthesematerialsforstrengtheningexistingconcretebridgesstartedinthe1980s,firstasasubstitutetobondedsteelplates,andthena
25、sasubstituteforsteeljacketsforseismicretrofitofbridgecolumns.CFRPCompositematerialsarecomposedoffiberreinforcementbondedtogetherwitharesinmatrix.Thefibersprovidethecompositewithitsuniquestructuralproperties.Theresinmatrixsupportsthefibers,protectthem,andtransfertheappliedloadtothefibersthroughsheari
26、ngstresses.MostofthecommerciallyavailableCFRPsystemsintheconstructionmarketconsistofuniaxialfibersembeddedinaresinmatrix,typicallyepoxy.Carbonfibershavelimitedultimatestrain,whichmaylimitthedefbrmabilityofstrengthenedmembers.However,undertrafficloads,localdebondingbetweenFRPsheetsandconcretesubstrat
27、ewouldallowforacceptablelevelofglobaldefonnationsbeforefailure.CFRPcompositescouldbeusedtoincreasetheflexuralandshearstrengthofbridgegirdersincludingpiercapbeams,asshowninFigure3.InordertoincreasetheductilityofCFRPstrengthenedconcretegirders,thelongitudinalCFRPcompositesheetsusedforflexuralstrengthe
28、ningshouldbeanchoredwithtransverse/diagonalCFRPanchorstopreventprematuredelaminationofthelongitudinalsheetsduetolocalizeddebondingattheconcretesurface-CFRPsheetinterface.InordertopreventstressconcentrationandprematurefractureoftheCFRPsheetsatthecornersofconcretemembers,thecornersshouldberoundedat50m
29、m(2.0inch)radius,asshowninFigure3.Deteriorationofconcretebridgemembersduetocorrosionofsteelbarsusuallyleadsinlossofsteelsectionanddelaminationofconcretecover.Asaresult,suchdeteriorationmayleadtoStructuraldeficiencythatrequiresimmediateattention.Figure4showsrehabilitationofstructurallydeficientconcre
30、tebridgepierusingCFRPcomposites.Figure3FlexuralandshearstrengtheningofconcretebridgepierwithFRPcompositesFigure4RehabilitationofdeterioratedconcretebridgepierwithCFRPcomposites6SummaryandconclusionsEvaluation,non-destructivetestingandrehabilitationofdeterioratedconcretebridgeswerepresented.Deteriora
31、tionofconcretebridgecomponentsduetocorrosionmayleadtostructuraldeficiencies,e.g.flexuraland/orshearfailures.ApplicationofCFRPcompositematerialsisbecomingincreasinglyattractivesolutiontoextendtheservicelifeofexistingconcretebridges.CFRPcompositescouldbeutilizedforflexuralandshearstrengthening,aswella
32、sforrestorationofdeterioratedconcretebridgecomponents.TheCFRPcompositesheetsshouldbewelldetailedtopreventstressconcentrationandprematurefractureordelamination.Forsuccessfulrehabilitationofconcretebridgesincorrosiveenvironments,acorrosionprotectionsystemshouldbeusedalongwiththeCFRPsystem.第十届东亚太结构工程设计
33、与施工会议2006年8月3-5号,曼谷,泰国碳纤维复合材料修复混凝土桥梁结构的详述及应用RiyadS.ABOUTAHA,tandNuttawatCHUTARAT2摘要：在各式各样的公路交通网络中，许多现有的古老桥梁，在各种恶劣的环境下，如更重的荷载和更快的车辆等条件下，依然在被使用着。冲刷、腐蚀和风化对这些古老的桥梁已经造成了破坏，而维修资金短缺更加剧了它们的损坏。一个利用碳纤维增强复合材料(CFRP)来延长混凝土桥梁的使用寿命的想法使桥梁恢复了原有的状态。然而，采用碳纤维复合材料修复受损混凝土桥梁的指导和标准还非常有限。在本文中对无损探伤、无损检测和利用碳纤维复合材料修复已遭侵蚀的桥梁的方法
34、进行了介绍。此设计对碳纤维增强混凝土桥的延性，及其应用后效果也进行了讨论和介绍。关键词:混凝土腐蚀，钢筋锈蚀，桥梁修复，碳纤维复合材料1简介在这里存在几个有害的外部环境因素影响着桥梁的耐久性。这些因素包括但又不仅限于化学物的侵蚀，受力钢筋的锈蚀，混凝土的碳化，化学物质的聚合反响。如果桥梁维护不好，这些因素可能导致结构的受损，如结构边缘不稳定或结构损毁。为了修复日渐恶化的现存桥梁，应当对其作彻底的评估。目的是通过大致检测剩余耐久度和承载力，评定出所有现存桥梁的真实情况。应用碳纤维复合材料可以恢复混凝土桥梁最初的状况并延长其使用年限。在北美、欧洲和日本，碳纤维复合材料应经得到深入的研究和广泛的应用
35、。碳纤维复合材料的几个设计指南也已经被应用于强化混凝土桥梁。然而，采用碳纤维复合材料修复损坏的混凝土桥梁的指导和标准还非常有限。本文通过适宜的例子给出了修复受损混凝土梁桥的准那么，列出了评估、无损检测、碳纤维复合材料复原受损混凝土桥梁。碳纤维复合材料的成功应用由于良好的细节设计，它主要考虑了集中力在碳纤维复合材料中依靠混凝土与碳纤维复合材料接触面间的粘合剂转移。此设计对碳纤维增强混凝土桥的延性和反响的效果也进行了讨论和介绍。2混凝土桥梁的损坏桥梁的使用年限应该给予极大地关注。越来越多的桥梁在到达设计使用年限之前出现令人侧目的破损。这些过早出现的损坏使得桥梁的结构可靠性和平安性成为1副教授,雪城
36、大学,美国2讲师,斯巴顿大学,泰国了值得考虑的问题。总的来说，桥梁的损坏与考虑它的花费多少是紧密相关的。在很多情况下，损坏问题的根源是混凝土结构中受力钢筋的腐蚀。通常由混凝土保护层预防受力筋的腐蚀。然而，这些具有代表性的问题，如混凝土质量差、不适当的设计或施工和周围恶劣的环境导致了钢筋的腐蚀。如果不及时处理像钢筋腐蚀这种耐久性问题，可能会引起受力不均问题，进而导致结构失稳，如图1所示。图1钢筋的锈蚀导致的结构失稳3损坏的混凝土梁桥墩柱的无损检测为了设计一个成功的新式系统，应该对桥梁现有的情况作彻底评估。评价现有桥梁的元素或体系需要翻看asbuilt图纸，才能准确的评估出现有桥梁的状况，如图2所
37、示。根据评估的目的，无损测试应该包括的内容：强度的检测，盐度，腐蚀率，混凝土中碱含量等等。虽然大多数的无损测试对现有桥梁不会造成任何损坏，一些无损检测可能导致的轻微局部损伤（如钻洞取芯），在无损检测完毕后应予以修复。这些测试也被叫作局检查法）；混凝土分层剥离锤击试验、超声波脉冲回波速度检查法、回音法）；缺陷和内部开裂（超声波脉冲回波速度检查法、回音法）；动态弹性模量（超声波脉冲回波速度检查法）；泊松比（超声波脉冲回波速度检查法）；混凝土板或墙的厚度（超声波脉冲回波速度检查法）；碳纤维复合材料剥离（锤击试验、红外线温度记录技术）；混凝土外表缺陷（外观鉴定）。质量和耐久性试验方法包括：钢筋锈蚀率一
38、现场试验，现场检测剖面氯化物，验定钢筋锈蚀率，测试钢筋电阻率，现场测定碱质与粒料反响活性，混凝土碱度测定（碳化测定），混凝土的渗透性（现场渗透性试验）。4损坏的混凝土梁桥墩柱的无损探伤对一个现有混凝土桥梁结构特征的评估由各种信息组成，如图纸、构筑物的检查记录，无损检测的分析数据和桥梁的结构分析。评估过程可以概括如下：（1）方案评估；（2）预备评估，主要包括现有文件检查、实地检查、材料检验和初步分析；（3）初步评估，主要有检查阶段，审查阶段和完成阶段。（4）有关本钱影响的分析。如果上述提供的信息，缺乏以用来进行高水平的评估。那么，我们做完上述的初步评估的步骤之后，可以再做一个详细的、深入的评估。
39、对于某个现存损坏的混凝土桥梁成功地分析评估应当考虑桥梁的实际情况及它的各局部的损坏程度。如果在适当的一段时间内很难完成如此详细的分析，那么就可能需要谈及的依靠现场试验得到的实际桥梁的评估。5碳纤维复合材料修复受损桥梁的应用碳纤维复合材料的应用延长了既有混凝土桥梁的使用年限而变得越来越引人注目。在桥梁的外部粘结碳纤维复合材料加强现有桥梁的技术被广泛应用在日本（纤维增强塑料板）和欧洲（多层纤维板）。在20世纪80年代，这些材料被应用于加强既有混凝土桥梁，最先是被用来替代钢板，后来被用来替代钢套作为桥墩的耐震补强。碳纤维复合材料由纤维强化复合材料与合成树脂基质粘结在一起组成。纤维以其独特的结构性能使
40、两者良好复合。树脂基质支撑并保护着纤维，将外施荷载以剪应力的方式传递给纤维。大局部在建筑市场上能买到的碳纤维复合材料加固系统都是由单向纤维嵌套在树脂基质中构成，最具代表性的是环氧树脂。碳纤维的有限的极限应变可能会限制强化涂层中的元素的形变能力。然而，在交通荷载作用下，结构在破坏之前且全局的形变在可接受的程度内，碳纤维复合材料板与混凝土基质之间局部的脱胶是被允许的。碳纤维复合材料可用于增加包括盖梁在内的桥主梁的抗弯及抗剪强度，如图3所示。为了增加碳纤维复合材料加强的混凝土主梁的延性，防止由于混凝土基质与碳纤维复合材料接触面之间产生局部脱胶而造成的纵向板过早剥离，应将用于增强抗弯强度的纵向碳纤维复合材料板、横向板及对角板互相锚固。为了防止在混凝土构件的转角处产生应力集中和碳纤维复合材料板过早断裂，这些转角应当是不小于50mm（2.0英寸）半径的圆角，如图3所示。
