中英改造现有的结构

山东建筑大学毕业设计外文文献及译文PAGEPAGE23外文翻译：RETROFITOFEXISTINGSTRUCTURES2.1IntroductionManystructureshavehistoricallybeenconstructedusingreinforcedconcrete.Typicalordinaryconcreteconsistsoffourconstituents:gravel,sand,water,andcement.Reinforcedconcretehassometypeofreinforcement,typicallysteel,combinedwithconcretetoproduceastrongersystemthanplainconcrete.Concreteisstrongincompressionbutweakintension.Tensileforcescauseconcretetocrackandeventuallyfailinabrittlemanneratstressessignificantlylowerthanthecompressionstrengthofconcrete.Steel,oranothertypeofreinforcementmaterial,canbeusedtocompensatefortheweaktensilestrengthofconcrete.Thissystemisreferredtoasreinforcedconcrete.Asreinforcedconcreteages,avarietyofdetrimentaleffectscanoccur.Theseincludespalling,flaking,orcrackingoftheconcrete,andsubsequentcorrosionofthereinforcingsteel.Theseoccurrencescansignificantlyaffectthestrengthofstructuralmembers.Membersdisplayingtheseadverseaffectsmayberehabilitatedusinganappropriateretrofitmethod.Retrofittingistypicallydonefortworeasons:rehabilitationorstrengthening.Aspreviouslydiscussed,rehabilitationisfixingthestructuraldeficienciesofadamagedstructureorstructuralmember.Thismaybenecessaryforagingmembersthatnolongerdisplaythestrengthoftheoriginaldesign.Strengtheningincreasestheload-carryingcapacityofastructuralmember(Ersoyetal.1993).Thismaybenecessaryifthesupportedloadisalteredthroughthelifeofthestructuralmember,orifcurrentdesignstandardshavemorestringentreinforcementrequirements.Additionally,structuralmembersinseismicregionsmayneedtobeupgradedtocurrentseismicrequirements.Retrofittingcanbeappliedtoanystructuralmembers,includingbeamsandcolumns.Severalmethodsaretraditionallyutilizedforretrofitting.Theseincludeconcretejacketing,steeljacketing,andFRPstrengthening(Wipfetal.1997).Reinforcementforconcretejacketscanbeprovidedbyrebarreinforcementorweldedwirefabric(WWF).Additionally,arelativelynewproduct,PrefabricatedCageSystemreinforcement(PCS),issuggestedasapossiblereinforcementalternativeforconcretejacketretrofits.品2珍.组2策捡湖P灭r峡e傍f巾a优b欧r立i杆c蝇a暮t脖e侧d沙导C验a黎g扮e敞匙S柴y厅s旅t赵e物m疾仆(零P书C汤S膜)辅异R荷e勾i便n茂f们o旷r讨c瞎e蠢m弱e汪n延t踪P回C厌S阁顾r纯e俭i格n厅f迅o丰r狼c岩e鹿m宋e典n透t剥,摩勿a尚s矛闪s敞h亩o缝w缺n党依i棕n立秤F勤i灵g让u拳r稼e并志2俊.荐1艘,歪英i赌s说漠e误s淋s肌e坛n席t芒i呼a慰l未l晶y丛距a堡税c蕉o昼n钥t前i腔n衣u伶o闲u日s炮然s努t瓜e泻e势l充满s舅e鞠c欲t肃i垦o管n卵脆w珍i手t绕h鱼捧h牲o勺l炮e致s幕沉a部p苏p萌l测i舰e潜d牢外a峡s佛统a净剃s南e趴c格o敏n轰d沿a智r慨y协随p饺r银o简c吼e拌s颂s纵.捎浸锋T摆h席e凭是P雀C右S普易r搭e沫i肿n槽f惊o挤r站c小e刑m拐e市n帐t祥光p疗r圆o华v束i救d跌e烛s概遥l涝o蚀n屿g篮i句t哈u眯d牛i挪n宴a胃l壁泥a帜n桑d增桐t风r默a适n好s壳v创e踩r曾s毫e勤冲r粘e亲i牲n渴f惭o筝r悼c颂e袭m匹e菜n澡t敌亲s势i刷m舰u器l么t厚a枕n赠e孝o忧u哪s秩l悬y券尘a缓n口d确面c表a绑n裁叼b市e蝴居u装s已e赚d喉画i栏n讨辟c徐i纽r锄c惰u音l拆a香r灵良o热r精距r还e热c畜t徒a焰n比g赴u做l妹a增r竟组s筑e洗c惠t焰i岛o狠n碎s询.拍骡膨T惑h显i愧s惩障m少o霞n偏o番l浊i搜t踏h积i嫂c防环c弄o罪n姑n骗e哭c务t冷i预o枣n芦迷r弟e尸d放u背c蚁e尽s宅适t禽h团e还顶n吓e亩e眉d溉崭f看o照r己固s绕e前p役a像r蛛a划t杀e库识l鞠o孔n芳g交i皂t角u悦d里i佣n港a翁l弄隐a窗n眨d超芬t糟r插a往n挽s宾v闹e柏r野s既e沟丑r铜e粗i太n集f聋o恶r穗c崇e代m版e坐n顶t坝.泛肉言P显C击S记答c势a晃n宣舟b霜e雕遣u醒s插e担d除洒a较s歇洒r怕e议i立n犹f雷o涨r喇c刮e堤m传e敢n明t胡衰i朵n散体c叮o键l遮u里m丢n灰s磁,薪荐s羞h胞e柿a师r弦归w捆a兽l厨l挪s吹,拘讲f副o私u谦n梅d陆a群t蔬i拨o倾n疗s葛械o踢r陷挥b条e她a勇m虎s毙.队果火P扯C砍S栏窄r鸡e森i针n带f姻o醉r牛c贺e舍m亮e味n菠t狂匪c脉a露n骆陵b贼e辞粗c错o美n片c源e链n言t芳r告i症c岩a丹l耀l庄y迹慌l倾a窝y草e尾r寒e怪d择践i呈f栋乓l睬a沟r缺g菜e换饼r柄e慨i然n候f睛o究r小c财e遣m燕e累n现t桌岁r参a城t喊i缺o针s员吉a卧r莫e晚吐r境e论q稀u烂i讨r却e轰d绣烤(同F钱i嘱g浆u芬r甩e盛建2产.蹲2冈)熊.舌烦懂F炒o京r滑气a钉仰c唤o挤l棍u乱m务n股,晚娱v巴e膛r渐t何i惯c跑a盲l裙许s拾t穷e俊e闷l骡厅s牲t闸r么i莲p迹s级血p军r仔o熔v刻i趣d上e喘装l剧o肥n红g眼i地t井u类d码i舟n芳a钟l钻绑r支e协i许n骆f既o茶r样c电e搜m欺e墙n彼t羊瞧w龟h哭i酷l太e毁带t惕h竖e刷梦h粥o秋r蚁i旧z响o椒n昆t姓a桥l斩亦s帜t举e拣e醒l腿岗s恐t尘r税i满p陡s倒俗p唉r馋o横v株i模d论e嫁级t科r馆a错n阀s厕v慨e悦r聚s哥e短疑r喘e钞i跨n始f雾o乘r喉c竞e悟m娘e遭n降t脚.卫释榜T贞e救s凳t辰s弯回h扇a歼v懂e忙桃s械h意o束w堡n猎垃t亩h衰a拥t音糊P烘C首S朱啄p引r雹o麻v雪i去d必e毛s廊新h馅i拔g百h戒e毒r毯剂c底o度n邪f影i非n笛e扁m涝e芒n最t地蒸c涝a内p始a佣c委i斜t哥i星e席s图悬t盒h烟a围n樱帖t金r茶a右d绩i并t旬i下o业n殖a养l组拳r奇e秆b扑a搅r港职r辨e强i丛n爽f格o辛r收c警e载m闸e较n魄t虽棒s岸y愈s王t寻e捕m踩s既狸(锤S闻h黎a踢m万s棕a战i巡搭a迟n消d臣不S纽e别z单e拳n剖做2痒0黑0签5鸭)悼.熄2佳.果2恩.捕1险浑闸乘P奋C劳S凡肚P臂r漂o早d暑u孟c活t饺i侵o恳n沃P伯C夜S汗短r获e传i忌n馒f脑o皱r茂c拘e诞m锤e荐n静t昏忽i宅s贩清p堂r呼o旨d狼u饺c盲e字d辱逃f假r用o订m亮嘱s遥t顷e紫e战l雀有t协u菊b牺e丧s刺衔o矮r帖见p喜l宋a霉t供e铸s均.汪洗晌S勿t蓝a奏n书d势a里r剥d扇尘s堪t等e撒e件l排光t竟u误b嗽e粉s晚杏o耕r兵般p消l粪a熟t款e售s害盒a常r良e飘岂p强u输n验c秘h秀e凶d都汽o此r穗勒c鸭u私t偶斥t面o凳辫p就r院o好v睁i妙d粗e漫信h第o来l始e嫌s喝衰w绩i漏t想h普夕t碍h浆e活惠d斑e箱s疑i饲r提e殃d咱靠d丘i狸m待e膜n铲s们i略o袭n勒s品.腾荷鸣I乌n汁酿l由i刮e船u妈文o院f捡香t敢u役b宋e怖s万,线话s备t诊e晓e虽l凡您p袋l过a案t示e锦s泰政c芝a完n勾计b侨e歉脾b汤e蓝n葱t绕栽i竞n块t兼o裕密t裁h框e我嗽r马e龄q治u让i虾r携e障d盈框s糖h积a托p扮e第炎a必n父d州哥t掏h事e泼n合广w索e缸l逝d舱e接d呀.介竿控C害a属s梦t任i市n绘g差脉o炼f肠撤P捆C伟S压遗r角e炼i露n堡f旧o蜜r真c概e班m捐e进n长t爬定h叫a搏s膜汗a况l非s哀o预脊b父e才e袜n爹蜡s言u廊g核g量e炼s题t仆e煮d鸟餐a域s膝勺a呢佳m景e团t耕h字o灰d茧误o排f优橡p宵r密o环d尾u冬c辈t婚i障o破n劫.段C量u萌t避t母i败n霞g论幅o秤f尖垄h告o摘l活e省s蹈滋i劝n嚼斯t乞h归e石族P苍C困S盆雾c勇a怀n壳宗b帝e鲜活p罚e非r恒f矮o时r办m棕e预d暑搁w地i值t申h控赤a乔扎v手a溉r降i其e壮t茎y浪困o严f别速m沈e漆t刑h彼o剃d透s乓纤i覆n另c冈l敌u经d泊i员n可g稠便l盗a考s虫e挨r任洽(溜a咸s吗部s姥h剃o懂w亩n剧坟i兄n爪谣F亿i召g牌u锐r帖e痕灯2捆.旋3鼠)虾,储傻p污l抓a逃s蜘m短a版,澡僵f胁l旅a驶m熟e蚕,彩龟a铁n非d顶毁a去b墨r本a甜s时i父v题e樱尘w保a快t汉e晋r铅吉j秃e步t签开c突u燕t奴t赌i目n蛮g孔.搏抹掏A披d可d历i覆t队i姐o川n赵a柏l备撕s齿u奔g用g越e战s削t牲e街d矮波m晒e理t往h环o趣d俩s糊怨i杂n桨c燥l妖u社d辰e近婚m捡i厉l姓l大i祥n慨g珠,闸塘e榜l氧e搜c套t霸r菠o谣c躬h燃e珠m析i厦c匪a厌l塘亡m永a词c踪h欧i进n佣i睁n恒g予,竖灯e请l逃e饰c自t已r行i锤c帅a贤l糕射d临i破s析c蚀h怠a蜜r帽g御e今每m他a独c以h下i晋n顽i率n瓣g僵,寇坝a点n弟d产列c恰h食e划m铃i秩c周a鞋l养伞e局t恰c境h播i私n祥g快.冻演竖P谦r旅e敲c恳i乔s揉i段o皆n际,须赏t揪i再m员e威,筒缺c乎o册s鞠t脱,熔竹a覆v娱a商i枣l更a厘b役i每l川i连t定y参,党贤a台n极d悬晒t纠h毁i球c仰k镜n系e告s闭s偷腐l说i汪m交i毁t岛a时t灿i厦o胁n品s甩格v守a关r影y深沾a待m旅o活n突g凉采t自h称e技剂d状i砖f耳f番e若r仓e药n赴t德蹈c禽u腐t时t催i悔n暗g丘绿m馆e外t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xialloadingaswellaslateralloading.Rebarhoopsareprovidedastheretrofitreinforcementfortheconcretejackets.Concretejacketsincreasethestrengthandstiffnessoftheas-built(unretrofittedorbase)columnsbyuptothreetimes.Itisalsoshownthatdamagebeforetheretrofithasnosignificantinfluenceontheperformanceofthejacketedcolumns.Overall,concretejacketswithrebarreinforcementsignificantlyimprovestiffness,strength,andductilityoftypicalreinforcedconcretecolumns,butconstructionisverylabor-intensive.SimilarresultsarereportedbyBettetal.(1988)forsimilarlyretrofittedcolumns.Threesquarecolumntestspecimensareconstructed,retrofittedwithaconcretejacket,andthentested.Oneofthespecimensistested,repaired,andthenretested.Theothertwospecimensarestrengthenedbeforetesting.Specimensaretestedunderaxialandlateralloadssimultaneouslytosimulateearthquakeloading.Again,theexperimentdeterminesthatadamagedretrofittedcolumnhasnearlythesamestrengthandstiffnessasanundamagedretrofittedcolumnwithasimilarconcretejacket.Lehman,etal.(2001)useconcretejacketstorepairseverelydamagedcolumns.Threerepairmethodsareconsideredandimplementedforthedamagedcolumns,whichwerebuilttomodernseismicspecifications.Initialdamagetothecolumnsincludescrushingofconcrete,bucklingandfractureoflongitudinalreinforcement,andfractureofthespiralreinforcement,whichwastheresultofaxialandlateralloading.Theconcretejacketretrofittedcolumndisplaysincreasedstiffnessandstrength,comparabletotheoriginalcolumnbeforedamage.2.3.1.2AdditionalReinforcementOptionsAdditionalreinforcementoptionsforconcretejacketinghavebeenintroduced.Weldedwirefabricisanothercommonmaterialthatcouldbeusedtoreinforceaconcretejacketretrofit.MorshedandKazemi(2005)proposeasimilarsystemproducedfromexpandedsteelmesh,showninFigure2.9.Theresearchdeterminesthatretrofittingmemberswiththeexpandedsteelmeshandmortarsignificantlyincreasestheshearstrengthandductilityoftheretrofittedmembers.2.3.2SteelJacketingSteeljacketspreventconcretefromexpandinglaterallyasaresultofhighaxialcompressionstrains.Thesteeljacketisequivalenttocontinuoushoopreinforcementandcanbeusedforcircularcolumnsorrectangularcolumnswithslightmodifications,asshowninFigure2.10.Steeljacketingofrectangularcolumnsisnotrecommendedbecausewhileshearstrengthisenhanced,flexuralductilityisonlyprovidedatthecorners.Anellipticalsteeljacketwithconcreteinfillshouldbeprovidedforrectangularmemberstofullyconfinealltheconcrete(Priestleyetal.1996).Acomprehensivetwo-partstudywasperformedbyPriestleyetal.(1994a,b)todeterminetheenhancedshearstrengthprovidedbysteeljacketretrofitting.Thefirstpartoftheresearchfocusesontheoreticalconsiderationsandtestdesign.ItisdeterminedthatACIdesignequationsareoverlyconservativeandnewdesignequationsarepresentedforcircularorrectangularcolumnsinneedofshearenhancement.Thesecondpartoftheresearchfocusesontheactualtestingofthecolumnsdesignedaccordingtotheproposedequations.Itisconcludedthatsteeljacketssignificantlyincreasetheshearstrengthandflexuralductilityofsheardeficientcolumns,whichisshowninTable2.1.SpecimenswithanAareas-builtcolumnsandanRrepresentsretrofittedcolumns.FurtherresearchperformedbyShamsandSaadeghvaziri(1997)determinesseveralneedsforresearchintoconcrete-filledsteeltubes(CFT).ItisconcludedthattheultimatestrengthofCFT’sisnotaccuratelypredictedandtheconfinementbenefitsneedtobeaccountedfor.Additionally,theresearchincludesaxialcompressiontestsperformedoncircularandrectangularCFTspecimens,showninFigure2.11.Itissuggestedthatfurtherresearchisneededtoaccuratelyunderstandthebondbetweenthesteelandconcrete,ductilityenhancement,andtoprovideanewdesignmethod.Aboutahaetal.(1999)usesvarioustypesofrectangularsteeljacketstostrengthenconcretecolumns.Thinsteelplatesarealsousedtomeasuretheconfinementandstrengtheningofthinplatesusedwithlargecolumns.Theresearchshowsthateventhinsteeljacketsareeffectiveforstrengtheningreinforcedconcretecolumns.Thesteeljacketsappliedincludefullandpartialsteeljackets,whichdonotfullyencompasstheentireretrofittedmember.Bothjacketsenhancetheductilityandstrengthofthemembers.Additionally,partiallystiffenedsteeljacketsareproposedbyXiaoandWu(2003a)toenhancestrengthandductilityforsquareorrectangularcolumns.Zhangetal.(1999)appliessteeljacketretrofitmeasurestypicallyusedforsinglecolumns,tomulticolumnbridgeapplications.Theretrofittedbridgestructureiscomparedtoanunretrofittedbridgestructureunderasimulatedseismicloadusingadynamicbridgeanalysisprogram.2.3.3FRPJacketingFiberreinforcedpolymer(FRP)confinementcanbeprovidedusingseveralcompositematerialsincludingfiberglass,carbonfiber,andKevlarbondedtotheconfinedconcretesurfaceusingepoxy(Priestleyetal.1996).Weightandcross-sectionoftheretrofittedmemberarenotsignificantlyaffectedwithFRPjackets.FRPjacketsaremostapplicableforcircularcolumns,asstressconcentrationscandevelopintheFRPwraparoundthecornersofsquareorrectangularcross-sections.FRPjacketscanbeusedforrectangularorothershapedmembers,ifshapemodificationisperformedtopreventstressconcentrationsfromdeveloping.TwotypesofFRPretrofits,wrapsandprefabricatedcompositejackets,aretypicallyutilized.2.3.3.1FRPWrapsFRPwrapshaveseveralbenefitsincludinghighstrength,lightweight,resistancetocorrosion,lowcost,andversatility(Saadatmaneshetal.1997).FRPwrappingisperformedbyfirstcleaningthesurfaceofthemembertoberetrofitted.EpoxyorresinisthenusedtoattachtheflexibleFRPfabrictothesurfaceofthemembertoberetrofitted.Thefabriccanbeapplieddry,butthepreferredmethodistosoakthefabricinepoxybeforeapplicationtoallowforbettercohesionwiththesurfaceofthemembertoberetrofitted.Thefabricisthensmoothedouttoensurenoairpocketsexistandextraepoxyissqueezedoutthesides.Anewlayerofepoxyshouldbeappliedbetweeneachlayeroffabricandafinallayerofepoxyontheoutermostsurfaceofthefabric.Thewrapshouldthenbeallowedtocureatambienttemperatures.Saadatmaneshetal.(1997)appliesFRPwrapstorepairseverelydamagedreinforcedconcretecolumns.CriticallystressedregionsnearthecolumnfootingjointarerepairedwithFRPwrap.ItisevidentfromtheresultsthatFRPcompositewrapseffectivelyrestoreflexuralstrengthandductilityindamagedcolumns.Similarly,Gergelyetal.(1998)usescarbonFRPwraptotesttheperformanceenhancementofreinforcedconcretecapbeamsandcapbeam-columnjoints.TheresearchshowsthatFRPwrapscansignificantlyincreasetheshearcapacityandductilityofcapbeamsandcapbeam-columnjoints.Hadi(2003)performssimilartestsonconcretebeamsandconcludesthatFRPwrapscontributetotheloadcarryingcapacity,aswellasflexuralstrength,ofreinforcedconcretebeams.AdditionallayersofFRPresultinincreasedflexuralstrength.XiaoandWu(2003b)performacomprehensiveresearchprogramtostudythebehaviorofconcreteconfinedbyvarioustypesofFRPwraps.CarbonfiberaswellasE-glasswrapsareinvestigated.Themethodsofapplicationvarybetweeninsitu(handlayup)andmachine-woundapplication.Again,itisdeterminedthatFRPcompositejacketssignificantlyincreasethestrengthandductilityofconcrete.2.3.3.2PrefabricatedFRPCompositePlatesFRPcompositeplatesaretypicallyshellsthatareprefabricatedinaquality-controlledenvironmentpriortofieldapplication.PrefabricatedFRPplatesareusedtoavoidthespecialattentionneededtoassurethaton-sitequalitycontrolandcuringconditionsarestrictlyenforced(XiaoandMa1997).Fiberreinforcementiscombinedwithresinandallowedtocureinthedesireddimensions,whichcreatesashell.Shellsareeitherfabricatedcontinuouslytoformamultilayerrollorcutintoindividualsingle-layercylindricalshellswithalongitudinalslitforeachlayer.Aftercuring,theshellsareopenedandclampedaroundthecolumntoberetrofitted.Adhesive,orepoxy,isthenappliedtobondtheshellstothecolumnsurface.Additionaladhesiveisappliedbetweeneachshelllayeralso.Slitsoftheindividuallayersarestaggeredtoavoidaconcentratedweakness(Xiaoetal.1999).XiaoandMa(1997)useprefabricatedglassfibershellstorepairfull-size,damaged,“asbuilt”columns.The“asbuilt”columnsareinitiallyfailedandthenretestedaftertheretrofitisapplied.Figure2.12displaysthetestset-upusedtoloadtheretrofittedcolumns.Theprefabricatedjacketsystemdelayscolumnfailurebyimprovingthehystereticresponseandincreasingtheductilityoftheretrofittedspecimens.Xiaoetal.(1999)continuethisresearchofprefabricatedFRPplatesbytestingplatesindividuallycuredandplatescuredtogetherasacontinuoussystem.Shearandductilityimprovementareverifiedforbothmethods,andlittleappreciabledifferenceisnoticedbetweenthetwosystems.AdditionalresearchisperformedbyShahroozandBoy(2004)tostrengthenbridgespanswithFRPplates.TheprefabricatedplatesarecomparedwithFRPfabric,asshowninFigure2.13.Testsareperformedtodeterminetheeffectivenessofthesystemsshortlyafterinstallationandagainayearlater.EffectivenessoftheFRPdidnotchangeintheoneyeartimeperiod.BothFRPretrofitsaresuccessfulinincreasingtheloadcarryingcapacityofthebridgeandthestiffness.Allretrofitmethodsdiscussedareshowntoincreasememberstrengthandconfinement.Thediscussedmethodshavebeenpreviouslytestedasretrofitsforreinforcedconcretecolumns.TheuseofPCSasreinforcementforconcretejacketshasnotpreviouslybeentested.Severalaspectsconsideredinevaluatingretrofitoptionsincludeapplication,confinement,cost,typeoffailure,bond,andconstructiontime.2.4.1ApplicationApplicationvariablesarefurtherdividedintoseveralfactorsthatcouldassistindeterminingthetypeofretrofittouse.Thesefactorsincludeconstructiontime,constructiondifficulty,andcuring.2.4.1.1ConstructionTimeTimerequiredforconcretejacketingisdependentuponthetypeofreinforcementused.Settingupformwork,creatingorsettingupreinforcement,pouringconcrete,andcuringoftheconcreteallcontributetothetimerequiredforthisretrofitting.PCSandweldedwirefabric(WWF)reduceconstructiontimebecausebothareproducedoff-site.ThetimerequiredtoproducePCSreinforcementisdependentonthemethodusedtocreatetheholes.WWFismassproducedandreadilyavailableonthemarket.SomeweldingmayberequiredforbothPCSandWWFtoenclosethemembertoberetrofitted.Rebarcageproductionisverytime-consumingwhetherproducedoff-siteorinthefield.Placementofthetransversereinforcementaroundthemembertoberetrofittedisalengthyprocessifmechanicalmeansarenecessarytoproperlypositionthereinforcement.Steeljacketsrequirelittleset-uptime.Noformworkisneededbecausethetubeservesasformwork.Littlefabricationandfieldtimeareneededfortheretrofit.Somefieldweldingmayberequiredtoenclosethemembertoberetrofitted.Pouringoftheconcrete,orgrout,doesnotrequiresignificanttime.FRPjacketsrequirepreparationofthesurfacetoberetrofitted.Forcircularsections,thistimeisminimal.Thesurfaceofthememberisthoroughlycleaned,andinsomecases,roughenedwithadiskgrinder.Forrectangularsections,allcornersorprotrudingedgesmustbesmoothedwhichcouldrequireadditionaltime.Iftherectangularcross-sectionistobealteredtoanellipticalshape,significanttimecouldberequiredforformworkset-up,concretepouring,andcuring.Actualapplicationofthematerialdoesnottakelong,asthematerialisapplieddirectlytothepreparedsurface.Closesupervisionisrequiredthroughoutcuringtoensurethatslidingorslippingofthematerialdoesnotoccur.Ifprefabricatedcompositeplatesareused,additionaltimeisrequiredforproductionandcuringoftheplates.2.4.1.2ConstructionDifficultyTheconstructionsequenceforconcretejacketconstructioncanbedividedintothreeparts:formwork,reinforcementapplication,andconcretecasting.Formworkissimilarforallconcretejacketingregardlessofthetypeofreinforcement.Difficultyinconcretecastingisafunctionofthetypeofmemberbeingretrofittedandspacingofthereinforcement.Closelyspacedreinforcementrestrictstheflowofconcreteandcreatesadditionalworktoensuretheconcreteisproperlydistributedthroughoutthemember.ProperclearancesallowconcretetoflowfreelythroughrebarcagesandWWFreinforcement.PCSrestrictsconcreteflowmorebecausethereinforcementprovidedisplanar,sothesurfaceareaconfiningtheconcreteisgreater.Ifproperclearancesareprovided,concreteflowisnotaproblem.Shotcrete,orthesprayingoflow-slumpconcrete,isanapplicationthatcouldpossiblyreducetheneedforformwork.Reinforcementapplicationisafactorsignificantlyaffectedbythetypeofreinforcementusedintheconcretejacket.WWFcaneasilybeplacedaroundthemembertoberetrofittedandthenweldedortiedtocreatethedesiredcage.Smallgaugewiresareeasilymanipulatedtothedesiredshape.Iflargeamountsofreinforcementareneeded,WWFwouldbespeciallyproduced,ormaynotbeaviableoptionatall.CircularPCScanbeplacedintwoC-sectionsandthenweldedtosurroundthemember.Placementofhooporspiralrebarreinforcementaroundanexistingmemberisadifficultandtimeconsumingprocessasmechanicalmeansmaybenecessarytobendthereinforcementintoplace.HoopreinforcementcanbelapsplicedorweldedastwoC-shapes,butthisisalsoatime-consumingprocess.Steeljacketsrequirethetwohalvesofthetubetobeweldedtogethertoencompassthemember.Noformworkisrequiredandtherearenoclearanceissuesbecausetheconcreteiscontainedwithinthetube.NoformworkorextraconcreteisrequiredforFRPretrofittingtypically.SurfacepreparationisveryimportantasFRPwrappingisverysensitivetostressconcentrationsandnecessarymeasuresmustbetakentoensuretheretrofitsurfaceisclean,butroughenoughtoprovideabondforthematerial.Itiscriticallyimportanttopreventanywrinklingorpocketingofthematerialduringapplication.Useofcompositeplatesreducethesesensitivities.Awetlay-uprequiresthefabrictobefullysaturatedbeforeapplication,whichmayrequiretheuseofamachine,tosoakandapplythewrap,tosignificantlyincreaseeaseofconstructionforlarge-scaleprojects.2.4.1.3CuringConcreteusedinsteeljacketsandconcretejacketsshould,preferably,beallowedtocureatmoderatetemperature.Freezingofconcreteduring