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1、ureAssumingathresholdof%initiationissecifiedforthefirstinsection,themodelsuggeststhatitshouldbeundertakenaftereightyearsAssumingthatinsectionindicatessignificantlylesscorrosioninitiation(egonlyabout%)andattributed,throughsiteinvestigations,toconcretecoverbeinghigherthanexected,arevisedredictionoftheerformancerofilemaybegeneratedTheidgemanagementactionsmaythenbealteredaccordinglyFigureillustratesh。

2、isisaroriateforthisursoseasifitcanreadilyincororateadditionaldata,udatingtherobabilityofreachingaerformancetargetTheconcetisanalogoustoudatingtherobabilityofarrivingontimewhilstonatrain,havingjustobtainsomeextrainformationregardingtheoeratingconditionsaheadTyicalresultsroducedbytherobabilisticdeteriorationmodelforacrossbeamchlorideexosurezone,similartothedelaminatedareashowninFigure,areshowninFig。

3、ttoolforconcreteidgesReinforcedconcretestructuresaresuscetibletoavarietyofdeteriorationmechanisms,includingalkalithawactionandchlorideingressSubstantialresearchhasbeenundertakeninrelationtothesemechanismsandotherroblemsThishasarticularlybeenthecaseoverthelastyearsorso,wheretheobjectivehasbeentoidentifycauses,consequencesanddeveloremediationstrategiesThishasimrovedunderstandingoflongtermbehaviouro。

4、freinforcedconcreteandresultedinthedevelomentoftechniquestoincreasedeteriorationresistanceAtresent,themostcommonaroachistoactafteraroblemhasbeenidentified,knownasreactivemaintenanceThismaynotbethemosteconomicsolutionsince,inmanycases,maintenanceismorecostlythanreventativetreatmentsHowever,ownersareoftenreluctanttoayforreventativetreatmentsbeforedeteriorationisaarentEarlyalicationoftreatmentsmayno。

5、geReliabilityanalysisinstructuralengineeringenablesquantificationofuncertaintiesassociatedwithloading,materials,deterioration,modelingandotherfactorsTheseareintegratedintoamethodthatestimatestherobabilityofreachingthesecifiederformancelevelduringtheservicelifeofastructureThemethodisincreasinglybeingusedinidgeengineering,bothforcaliationofsafetylevelsincodesandstandardsandimrovingandrefiningassess。

6、iticalReliabilityanalysishasemergedasanimortanttoolinthismultiobjectivemanagementrocess,whichmusttakeintoaccountsafety,functionalityandsustainabilitycriteriaInsimleterms,thereliabilityofastructureorasystemistherobabilityofachievingaarticularerformancelevelProbabilityorlikelihoodisthearoriatemeasure,sinceallengineeringsystemsaresuscetibletouncertainties,arisingfromrandomhenomenaandincomleteknowled。

7、ventativetreatmentsHowever,ownersareoftenreluctanttoayforreventativetreatmentsbeforedeteriorationisaarentEarlyalicationoftreatmentsmaynotbetheotimalsolutioninthelongrunIntegrateddeteriorationanderformanceredictionmodelingisessentialtoroactivelylanandrioritiseinsection,testingandmaintenanceThisbecomesincreasinglyimortantasinfrastructureagesandjustificationformaintenancefundingbecomesincreasinglycr。

8、ible,thestateofthestructureByintegratingredictivedeteriorationmodelswithassessmenttoolsanderformancecriteria(atelement,structureorgroulevel)itbecomesossibletobasethemaintenanceregimeontimedeendenterformancerofilesThisisarticularlyrelevantinthecontextofwholewifecostingroceduresSubstantialresearchhasbeenundertakeninrelationtothesemechanismsandotherroblemsThishasarticularlybeenthecaseoverthelastyear。

9、mentmethodologiesTheuroseofthisarticleistooutlineitsalicationinmanagingidgessuscetibletodeteriorationAlthoughdataformanydeteriorationvariablescanbederivedfromlaboratorystudies,thereisanabsenceofsimilardatarealstructuresAnimortantfeatureofthemodelisthefacilitytomodifyinitialredictions,basedonublished(knownas‘rior’)data,usinginformationanddataobtaineddirectlyfromtheactualstructuresReliabilityanalys。

10、owalimitstaterofileforthiszonechangeswithassumedconditionsThedeteriorationmodelhasbeenintegratedwithbondlimitstateequationsThus,assumingthatthecomonenthasatargetnominalrobabilityoffailureoferyear,rofilesuggestsalifetimeofonlytoyears,whereasProfilesuggeststoyearsBothareshortlifetimeswhencomaredwiththenormallifeexectancyofidgesHowever,initialconditionsrelatingtotheseresultsassumethatthedeckjointhas。

11、sorso,wheretheobjectivehasbeentoidentifycauses,consequencesanddeveloremediationstrategiesThishasimrovedunderstandingoflongtermbehaviourofreinforcedconcreteandresultedinthedevelomentoftechniquestoincreasedeteriorationresistanceAtresent,themostcommonaroachistoactafteraroblemhasbeenidentified,knownasreactivemaintenanceThismaynotbethemosteconomicsolutionsince,inmanycases,maintenanceismorecostlythanre 。

12、tbetheotimalsolutioninthelongrunIntegrateddeteriorationanderformanceredictionmodelingisessentialtoroactivelylanandrioritiseinsection,testingandmaintenanceThisbecomesincreasinglyimortantasinfrastructureagesandjustificationformaintenancefundingbecomesincreasinglycriticalPerformanceassessmentcanbeachievedthroughsurveys,testingandformalcalculations,ideallybasedonsitedatathatreresent,asaccuratelyasoss