NCHRP 12NCHRP 12--8282 Developing ReliabilityDeveloping ...

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NCHRP 12NCHRP 12--8282Developing ReliabilityDeveloping Reliability--Based Bridge InspectionBased Bridge Inspection

PracticesPractices

Glenn A. Washer, Ph.D., P.E.Glenn A. Washer, Ph.D., P.E.

AASHTO TECHNICAL COMMITTEE FOR BRIDGEAASHTO TECHNICAL COMMITTEE FOR BRIDGEMANAGEMENT, EVALUATION ANDMANAGEMENT, EVALUATION AND

REHABILITATION (TREHABILITATION (T--18)18)

Tuesday July 7, 2009Tuesday July 7, 2009

AgendaAgenda

•• BackgroundBackground

•• IntroductionIntroduction

•• ObjectiveObjective

•• Proposed approachProposed approach

•• Research teamResearch team

•• StatusStatus

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BackgroundBackground•• Current NBIS require routine inspections every 24Current NBIS require routine inspections every 24

monthsmonths–– extension to 48 months for bridges that meet certain criteriaextension to 48 months for bridges that meet certain criteria

and approved by the FHWAand approved by the FHWA–– Reduced frequency based on riskReduced frequency based on risk

•• Under the calendarUnder the calendar--based system, recently constructedbased system, recently constructedbridges are inspected at the same frequency as olderbridges are inspected at the same frequency as olderbridge that may be reaching the end of their service livesbridge that may be reaching the end of their service lives–– 83% of bridges are on 24 month cycles (2006 C & P)83% of bridges are on 24 month cycles (2006 C & P)–– Assessment of theAssessment of the ““fitness for servicefitness for service”” of the bridge is notof the bridge is not

included in inspection planningincluded in inspection planning–– Resources are invested in reResources are invested in re--inspection of bridges that mayinspection of bridges that may

not be justifiednot be justified•• New bridges in good conditionNew bridges in good condition•• Standard bridges with proven track records, experience and wellStandard bridges with proven track records, experience and well

understood deterioration modesunderstood deterioration modes

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BackgroundBackground•• Other countries are using much longer inspection intervals to enOther countries are using much longer inspection intervals to ensuresure

safety of bridgessafety of bridges–– 5 to 8 yr inspection cycles5 to 8 yr inspection cycles–– Based on assessment inspection needs (damage modes present orBased on assessment inspection needs (damage modes present or

expected, bridge design, age, condition etc.)expected, bridge design, age, condition etc.)–– More inMore in--depth inspection scope, conducted less frequentlydepth inspection scope, conducted less frequently–– Interim, lowInterim, low--intensity inspections by maintenance/transportation agencyintensity inspections by maintenance/transportation agency

employees (damage, routine maintenance needs etc.)employees (damage, routine maintenance needs etc.)

•• Focus on damage modes present, not effectsFocus on damage modes present, not effects–– Assessment of progression and root cause of damage toAssessment of progression and root cause of damage to

•• Identify maintenance/repair requirementsIdentify maintenance/repair requirements•• Determine inspection and surveillance needs based on existing orDetermine inspection and surveillance needs based on existing or expectedexpected

deterioration modesdeterioration modes

•• Qualifications of inspection teams considered in decision makingQualifications of inspection teams considered in decision makingprocessesprocesses–– More complex bridges requiring more advanced qualification ofMore complex bridges requiring more advanced qualification of

inspection teamsinspection teams

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IntroductionIntroduction

•• A new inspection paradigm is needed to:A new inspection paradigm is needed to:

–– Improve bridge safety and reliabilityImprove bridge safety and reliability

–– Improve the effectiveness of maintenance andImprove the effectiveness of maintenance andpreservation activitiespreservation activities

–– Focus inspection resources on the most atFocus inspection resources on the most at--riskriskbridgesbridges

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ObjectiveObjective

•• Develop a recommended bridge inspectionDevelop a recommended bridge inspectionpractice based on rational methods to ensurepractice based on rational methods to ensurebridge safety, serviceability and effectivebridge safety, serviceability and effectiveuse of resourcesuse of resources

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IntroductionIntroduction

•• A rational approach to determining bridgeA rational approach to determining bridgeinspection frequencies would consider:inspection frequencies would consider:–– Structure typeStructure type–– AgeAge–– MaterialsMaterials–– Current conditionCurrent condition–– Exposure environmentExposure environment–– LoadingLoading–– Prior maintenance and/or safety issuesPrior maintenance and/or safety issues–– Prior experience and knowledgePrior experience and knowledge

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Research ApproachResearch Approach

•• Methodology proposed utilizes a riskMethodology proposed utilizes a risk--based frameworkbased frameworkto identifyto identify–– Appropriate inspection frequencyAppropriate inspection frequency–– Inspection scope and intensityInspection scope and intensity

•• Routine, inRoutine, in –– depth, enhanced indepth, enhanced in--depthdepth•• Use of NDE and other testingUse of NDE and other testing

–– Systematic methodology that is based onSystematic methodology that is based on•• Expert opinionExpert opinion•• ExperienceExperience•• Qualitative and quantitative assessmentsQualitative and quantitative assessments

•• API 580, ASME, NASA, etc.API 580, ASME, NASA, etc.•• 48 month / reduced inspection frequency48 month / reduced inspection frequency

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Reliability/Risk AssessmentReliability/Risk Assessment

•• Proposed approach has a twoProposed approach has a two--step evaluation process:step evaluation process:•• Assessment of bridge inventory to classify bridge populationAssessment of bridge inventory to classify bridge population

–– Identify bridges with high reliability (low risk)Identify bridges with high reliability (low risk)•• Candidates for extended inspection frequencyCandidates for extended inspection frequency

–– Identify bridges for which extended inspection frequencies mayIdentify bridges for which extended inspection frequencies maynot be appropriatenot be appropriate

•• Fracture critical, low condition ratings, age, unique design chaFracture critical, low condition ratings, age, unique design characteristicsracteristics

•• Failure modes, effects and criticality analysis (FMECA)Failure modes, effects and criticality analysis (FMECA)–– Specific, bridgeSpecific, bridge--byby--bridge assessmentbridge assessment–– Evolutionary framework for incorporating deterioration data,Evolutionary framework for incorporating deterioration data,

expert opinion, data on inspection capabilities and effectivenesexpert opinion, data on inspection capabilities and effectiveness,s,etc.etc.

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Risk MatrixRisk Matrix

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Catastrophic High risk

Critical Medium risk

Major Low risk

Moderate

Minor

Unlikely Remote Occasional Probable Frequent

•• Proposed methodology would assess risk based onProposed methodology would assess risk based onlikelihood and severity of damagelikelihood and severity of damage

•• Qualitative and/or semiQualitative and/or semi--quantitative risk assessmentquantitative risk assessment

•• Incorporate inspection methods and capabilitiesIncorporate inspection methods and capabilities

Process Flow ChartProcess Flow Chart

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Reliability/Risk Analysis of Bridge PopulatonBridge Design CharacteristicsAge, MateriallCurrent load and component ratingScour ratingImportanceEnvironment

DATAQuantitative: Deterioration curves from NBI, Pontis, LiteratureQualitative Experience / historical performanceProgrammatic (NHS. STRAHNET, etc.) importance

Extendedinspection period

Reliability:High

Standard 24months interval

Reliability:Medium

Deck - CorrisionDamage

PS Concrete GirderPrestress loss

PS Concrete GirderCorrosion

ElastomericBearing

Inspection Scope and IntervalIntensity of inspectionInspection technologiesEstimated reliability/confidenceInspection results

Reduced 12Frequency

Reliability:Low

Failure Modes, Effects and Criticality Analysis (FMECA)

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Risk PrioritizationRisk Prioritization

•• Utilize a systematic prioritization methodology forUtilize a systematic prioritization methodology forclassifying bridges accordingclassifying bridges according–– Specific damage modesSpecific damage modes

•• SeveritySeverity•• Effect on safety and durabilityEffect on safety and durability

–– OccurrenceOccurrence•• Likelihood of damage mode, extent etc.Likelihood of damage mode, extent etc.•• Based on expert opinion (experience), age, deterioration data,Based on expert opinion (experience), age, deterioration data,

evolving data (LTBPP), probability of failure analysis, etc.evolving data (LTBPP), probability of failure analysis, etc.

–– Detectability factorsDetectability factors•• Scope of inspectionScope of inspection•• Application of NDE or physical testingApplication of NDE or physical testing•• Reliability of inspection approachReliability of inspection approach

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ChallengesChallenges

•• Develop methodology that is practically implementableDevelop methodology that is practically implementablewith existing programswith existing programs–– ResourcesResources–– Capitalizes on experience and expert knowledgeCapitalizes on experience and expert knowledge

•• Allow StateAllow State’’s to capitalize on existing data resourcess to capitalize on existing data resources

–– FlexibilityFlexibility–– Allows for qualitative and quantitative assessmentAllows for qualitative and quantitative assessment

•• EvolutionaryEvolutionary

–– Provide a framework that allows for advanced analysis toProvide a framework that allows for advanced analysis todetermine various risk factors, such asdetermine various risk factors, such as

•• Deterioration modelingDeterioration modeling•• Advanced reliability analysisAdvanced reliability analysis•• Advancements in inspection technologiesAdvancements in inspection technologies

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Research TeamResearch Team

•• G. Washer, MissouriG. Washer, Missouri

•• R. Connor, PurdueR. Connor, Purdue

•• A. Ciolko, CTL GroupA. Ciolko, CTL Group

•• P. Fish, Fish & Assoc. Inc.P. Fish, Fish & Assoc. Inc.

•• R. Kogler, Rampart LLCR. Kogler, Rampart LLC

•• D. Forsyth, Texas Research International (TRI)D. Forsyth, Texas Research International (TRI)–– Pipeline/aerospace inspection reliability expertPipeline/aerospace inspection reliability expert

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StatusStatus

•• Project is in initial stagesProject is in initial stages–– First tasks ofFirst tasks of

•• Literature searchLiterature search•• Review of existing reliability/risk based inspection processes (Review of existing reliability/risk based inspection processes (API,API,

ASME, NASA, etc.)ASME, NASA, etc.)•• Identifying data, characteristics and criteria that should be usIdentifying data, characteristics and criteria that should be used fored for

rational bridge inspection practicesrational bridge inspection practices•• Applicability of reliability theoryApplicability of reliability theory•• Identification of technical and policy issues that could restricIdentification of technical and policy issues that could restrictt

implementationimplementation

–– Developing updated work plan for developing reliability basedDeveloping updated work plan for developing reliability basedpracticespractices

•• Schedule : Interim report due Sept. 09, Final report Dec. 2010Schedule : Interim report due Sept. 09, Final report Dec. 2010–– FastFast--movermover

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Questions?Questions?

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Final Report:Final Report: NCHRP 20NCHRP 20--07(252)07(252)Guideline for Implementing Quality Control andGuideline for Implementing Quality Control andQuality Assurance for Bridge InspectionQuality Assurance for Bridge Inspection