Structural Health MonitoringStructural Health MonitoringStructural Health MonitoringStructural Health Monitoring

OutlineOutlineOutlineOutline

IntroductionIntroduction IntroductionIntroduction Components of structural health in civil Components of structural health in civil

i i (SHCE)i i (SHCE)engineering (SHCE)engineering (SHCE) SHCE and multiSHCE and multi--disciplinary aspectsdisciplinary aspects NDE/NDT vs. SHCENDE/NDT vs. SHCE ExamplesExamplesExamplesExamples Trends affecting SHCETrends affecting SHCE

Cl i kCl i k Closing remarksClosing remarks

IntroductionIntroductionIntroductionIntroduction

Structural Health in Civil EngineeringStructural Health in Civil Engineering Structural Health in Civil Engineering Structural Health in Civil Engineering (SHCE) is monitoring structural behavior on (SHCE) is monitoring structural behavior on both time and space basis with minimalboth time and space basis with minimalboth time and space basis, with minimal both time and space basis, with minimal human involvement, for effective decisionhuman involvement, for effective decision--making to meet infrastructure managementmaking to meet infrastructure managementmaking to meet infrastructure management making to meet infrastructure management objectives. objectives.

Increase safetyIncrease safety Increase safetyIncrease safety Optimal costs (shortOptimal costs (short--term, lifeterm, life--cycle, project, cycle, project,

and network levels)and network levels)and network levels)and network levels)

Source: Ettouney and Alampalli, Infrastructure Health in Civil Engineering, CRC Press, 2011

SHM ApplicationsSHM ApplicationsSHM ApplicationsSHM Applications Structural DemandStructural Demand

Type of hazards (natural and manType of hazards (natural and man--made)made) Hazard magnitude and frequencyHazard magnitude and frequency ConsequencesConsequences ConsequencesConsequences Can be used in planning, design, and developing Can be used in planning, design, and developing

inspection and maintenance guidelinesinspection and maintenance guidelinesp gp g

Structural CapacityStructural Capacity SafetySafetySafetySafety InIn--Service condition and extent => CapacityService condition and extent => Capacity StabilityStability

SHM ApplicationsSHM ApplicationsSHM ApplicationsSHM Applications Performance Based EngineeringPerformance Based Engineering

Risk (hazards probability and consequence)Risk (hazards probability and consequence) MitigationMitigation Acceptance limitsAcceptance limits All the above vary depending on hazardAll the above vary depending on hazard Correlations between hazards should be Correlations between hazards should be

considered carefullyconsidered carefully

SHCE ComponentsSHCE ComponentsSHCE ComponentsSHCE Components

SHCE has four distinct and integratedSHCE has four distinct and integrated SHCE has four distinct and integrated SHCE has four distinct and integrated components:components:

M t d t ll tiM t d t ll ti Measurements or data collectionMeasurements or data collection Structural identificationStructural identification

D d t tiD d t ti Damage detectionDamage detection Decision makingDecision making

SHCE Components: Baseball AnalogySHCE Components: Baseball AnalogySHCE Components: Baseball AnalogySHCE Components: Baseball AnalogySecond Base

Damage Identification:Global vs. LocalTypeExtentEffect on the system

Structural Identification:Modal IdentificationParameter IdentificationNon-Physical (Neural Networks)Other?

Decision Making is the key part of the SHCE

D i i M ki M t

First BaseThird Base

Decision-Making:Do nothingMaintenance (type, timing)Repair (simple, extensive)Replace (Decommission)

Measurements:SensorsInstrumentationTechnologies

Home Plate

BASEBALL PARADIGM of SHCE (Structural Health in Civil EngineeringEngineering

MeasurementsMeasurementsMeasurementsMeasurements

SensorsSensors SensorsSensors InstrumentationInstrumentation Data collectionData collection Data analysisData analysisyy

Traditional Sensors

Strain gages

LVDTs Accelerometers

Structural IdentificationStructural IdentificationStructural IdentificationStructural Identification

Understand structural behaviorUnderstand structural behavior Understand structural behaviorUnderstand structural behavior Dynamic, static, or both (depends on loading)Dynamic, static, or both (depends on loading) Variety of methods (common sense to FEM/BEM)Variety of methods (common sense to FEM/BEM) Variety of methods (common sense to FEM/BEM)Variety of methods (common sense to FEM/BEM)

Use measurementsUse measurements Validate/calibrate structural modelValidate/calibrate structural model Validate/calibrate structural modelValidate/calibrate structural model Understand differences between actual and Understand differences between actual and

designed/modeled behaviordesigned/modeled behaviorgg

Translate measurements to meaningful Translate measurements to meaningful structural parameters/statesstructural parameters/statesstructural parameters/statesstructural parameters/states

Structural IdentificationStructural IdentificationStructural IdentificationStructural Identification Modeling aspects depend onModeling aspects depend on

Loading typeLoading type MeasurementsMeasurements Damage identification methodsDamage identification methods Damage identification methodsDamage identification methods Coarseness of the resultsCoarseness of the results Use of model after the initial decisionUse of model after the initial decision--makingmakingUse of model after the initial decisionUse of model after the initial decision makingmaking

Complicated or fine models does not mean Complicated or fine models does not mean they are betterthey are betterthey are betterthey are better

Loading interactions and boundary Loading interactions and boundary conditions are very importantconditions are very importantconditions are very importantconditions are very important

Damage IdentificationDamage IdentificationDamage IdentificationDamage Identification

IdentifyIdentify IdentifyIdentify Did damage occur?Did damage occur? Where? How much?Where? How much? Where? How much?Where? How much? Implications/Consequences?Implications/Consequences?

Types of damageTypes of damage Types of damageTypes of damage FatigueFatigue CorrosionCorrosionCorrosionCorrosion Wear and TearWear and Tear Large Deformation (impact, Large Deformation (impact, delaminationdelamination, etc), etc)

Damage IdentificationDamage Identificationgg

Type of damagesType of damagesD tilD til DuctileDuctile Higher deformationsHigher deformations Better suited for SHCE applicationsBetter suited for SHCE applications Better suited for SHCE applicationsBetter suited for SHCE applications Baseline data essentialBaseline data essential

BrittleBrittle BrittleBrittle Sudden and little or no deformation until failureSudden and little or no deformation until failure Not suitable for SHCE applicationNot suitable for SHCE applicationNot suitable for SHCE applicationNot suitable for SHCE application

ProgressiveProgressive Higher deformationsHigher deformationsgg SHCE may be usefulSHCE may be useful Higher probability of system failureHigher probability of system failure

Damage IdentificationDamage IdentificationDamage IdentificationDamage Identification

DecisionDecision--MakingMakingDecisionDecision MakingMaking

Given all information from sensing, Given all information from sensing, SI and Damage ID:SI and Damage ID:

What to do?What to do? Maintain, repair , retrofit , replaceMaintain, repair , retrofit , replace Make (no) changes to future designsMake (no) changes to future designs

All phases should be based on aAll phases should be based on a All phases should be based on a All phases should be based on a benefit (Value) benefit (Value) Cost analysisCost analysis

SHCE is truly a multiSHCE is truly a multi--disciplinary effort and disciplinary effort and i l l t k h ld i l ti l l t k h ld i l tinvolves several stakeholders involvement involves several stakeholders involvement at all stages: planning before bridge is built at all stages: planning before bridge is built

t b id l ft i lift b id l ft i lifto bridge removal after service lifeto bridge removal after service life

SHCE SHCE StakeholdersStakeholders

Structural Engineer Regulators Structural Engineer Vendors Consultants Materials Hazard Specialist

Planners

Regulators Government Owners Risk Managers Users

Other Planners Other...

Engineering DecisionMakers

EnforcementsFi

Other Business

First Responders Inspection Construction Research Other...

Finance Marketing Management Economists IT

SHCE vs. NDTSHCE vs. NDTSHCE vs. NDTSHCE vs. NDT

IssueIssue NDTNDT SHCESHCE

Sensing / Sensing / Localized. Need a good idea Localized. Need a good idea Generally covers larger Generally covers larger g /g /MeasurementsMeasurements

ggas to the location of as to the location of damage (sensing damage (sensing locations). Mostly a locations). Mostly a

y gy garea. Location of damage is area. Location of damage is not known a priori. Can be not known a priori. Can be continuous monitoring or continuous monitoring or

localized event in time.localized event in time.

Sensing technology is very Sensing technology is very

periodic longperiodic long--term term monitoring.monitoring.

Sensing technology is very Sensing technology is very advancedadvanced

Mostly manualMostly manual

Sensing technology is Sensing technology is developing.developing.

Mostly manualMostly manual

SHCE vs. NDTSHCE vs. NDTSHCE vs. NDTSHCE vs. NDTIssueIssue NDTNDT SHCESHCE

Structural Structural (System) (System) IdentificationIdentification

Structural Id. Methods Structural Id. Methods use only limited subset of use only limited subset of NDT methods since NDT methods since

Structural Id. Is an Structural Id. Is an integral part of many of integral part of many of SHM projectsSHM projectsIdentificationIdentification NDT methods since NDT methods since

Structural Id. deals with Structural Id. deals with global structural global structural behavior rather than behavior rather than

SHM projects.SHM projects.

Structural Id. Methods are Structural Id. Methods are ffbehavior, rather than behavior, rather than

localized structural localized structural regions.regions.

well developed for simple well developed for simple structures and special structures and special structures cases. Need structures cases. Need

l l ti l l ti Need to make better Need to make better utilization of NDT utilization of NDT methods for Structural methods for Structural

more general solutions more general solutions that can be robust for that can be robust for general situations.general situations.

methods for Structural methods for Structural

SHCE vs. NDTSHCE vs. NDTSHCE vs. NDTSHCE vs. NDT

IssueIssue NDTNDT SHCESHCE

Damage Damage Localized. If type and Localized. If type and Efficient solutions needs Efficient solutions needs ggIdentificationIdentification

ypypapproximate location of approximate location of damage is known, damage is known, would give accurate would give accurate

developingdeveloping

Damage location can be in Damage location can be in results.results.

Due to localized nature, Due to localized nature,

Damage location can be in Damage location can be in a wider area.a wider area.

R i i f ti R i i f ti Due to localized nature, Due to localized nature, global structural global structural information is not information is not needed.needed.

Requires more information Requires more information regarding structure regarding structure (geometry, properties, (geometry, properties, etc )etc )eededeeded etc.)etc.)

SHCE vs. NDTSHCE vs. NDTSHCE vs. NDTSHCE vs. NDT

IssueIssue NDTNDT SHCESHCE

DecisionDecision--MakingMaking Many tools are Many tools are More involved More involved gg yyavailable for NDE.available for NDE. decisiondecision--making making

tools and processes tools and processes are needed, due to are needed, due to the global nature the global nature (both in space and (both in space and time) of SHCE.time) of SHCE.

SHM Current UsesSHM Current UsesSHM Current UsesSHM Current Uses

Verification/validation ofVerification/validation of Verification/validation of Verification/validation of Advanced technologiesAdvanced technologies Innovative materialsInnovative materialsInnovative materialsInnovative materials Analytical methodsAnalytical methods Guidelines and design proceduresGuidelines and design procedures

Augment bridge inspections by making inspection Augment bridge inspections by making inspection more quantitativemore quantitative

Improve load ratings and remove Improve load ratings and remove postingspostings

Remote Bridge Monitoring SystemsRemote Bridge Monitoring SystemsRemote Bridge Monitoring SystemsRemote Bridge Monitoring Systems

Second generationSecond generation RBMSRBMS installed on twoinstalled on two Second generation Second generation RBMSRBMS installed on two installed on two bridges in Roscoe, NYbridges in Roscoe, NY

Installed in 1992Installed in 1992 Installed in 1992Installed in 1992 Central monitoring unitCentral monitoring unit 16 smart sensor units (16 smart sensor units (ssussu))16 smart sensor units (16 smart sensor units (ssussu))

Data communication controlData communication control Memory managementMemory management

Si lSi l t ffi di ti t lt ffi di ti t l SignalSignal--traffic direction controltraffic direction control User selectable sampling speedUser selectable sampling speed Memory to store five data record (16,384 points)Memory to store five data record (16,384 points)

Strain gages, inclinometers, and accelerometersStrain gages, inclinometers, and accelerometers

Remote Bridge Monitoring SystemsRemote Bridge Monitoring SystemsRemote Bridge Monitoring SystemsRemote Bridge Monitoring Systems

RBMSRBMS Roscoe NYRoscoe NY RBMSRBMS, Roscoe, NY, Roscoe, NY Weather proofed enclosures for sensor and system Weather proofed enclosures for sensor and system

boxesboxesboxesboxes Modem with telephone lineModem with telephone line Power connection with 48Power connection with 48--hr battery backuphr battery backup Lithium battery with 10Lithium battery with 10--yr life system yr life system configconfig. storage. storage Remote calibration capabilityRemote calibration capability Data triggersData triggers Data analysis options (Data analysis options (FFTFFT, histograms, etc.), histograms, etc.) Warning alarms based on defined criterionWarning alarms based on defined criterion Warning alarms based on defined criterionWarning alarms based on defined criterion

Remote Bridge Monitoring SystemsRemote Bridge Monitoring SystemsRemote Bridge Monitoring SystemsRemote Bridge Monitoring Systems Primary ObjectivesPrimary Objectives

Examine the reliability of stateExamine the reliability of state--ofof--the art remote the art remote bridge monitoring systems available at the inception bridge monitoring systems available at the inception of this study.of this study.yy

Examine utility of remote monitoring systems for Examine utility of remote monitoring systems for continuous bridge monitoring.continuous bridge monitoring.

Determine the viability of remote bridge monitoring Determine the viability of remote bridge monitoring system for damage detection.system for damage detection.

Secondary ObjectiveSecondary Objective Secondary ObjectiveSecondary Objective Monitor inMonitor in--service structural behavior and effects of service structural behavior and effects of

rehabilitationrehabilitationrehabilitation.rehabilitation.

Remote Bridge Monitoring SystemsRemote Bridge Monitoring SystemsRemote Bridge Monitoring SystemsRemote Bridge Monitoring Systems

Scour Monitoring in Long IslandScour Monitoring in Long Island Robert Moses Causeway over Fire Island Robert Moses Causeway over Fire Island

Inlet and Wantagh Parkway over GooseInlet and Wantagh Parkway over GooseInlet and Wantagh Parkway over Goose Inlet and Wantagh Parkway over Goose CreekCreek Tidal scour has been an issueTidal scour has been an issueTidal scour has been an issueTidal scour has been an issue Scour monitors at several piersScour monitors at several piers

Record stream bed elevationRecord stream bed elevationRecord stream bed elevationRecord stream bed elevation Master control stationMaster control station A remote station at each instrumented pierA remote station at each instrumented pierpp A water temperature sensorA water temperature sensor A water stage sensorA water stage sensor An automatic alerting systemAn automatic alerting system

Scour Monitoring in Long IslandScour Monitoring in Long Island Robert Moses Causeway over Fire Island Robert Moses Causeway over Fire Island

Inlet and Wantagh Parkway over GooseInlet and Wantagh Parkway over GooseInlet and Wantagh Parkway over Goose Inlet and Wantagh Parkway over Goose CreekCreek Scour monitors at several piersScour monitors at several piersScour monitors at several piersScour monitors at several piers

Data collection interval can be variedData collection interval can be varied The data gathered round the clock during scour The data gathered round the clock during scour g gg g

eventsevents The accuracy checked with scheduled diving The accuracy checked with scheduled diving

i tii tiinspectionsinspections Cautionary or critical scour elevations to trigger Cautionary or critical scour elevations to trigger

warning messages to the engineers as needed.warning messages to the engineers as needed.g g gg g g

FRP ColumnFRP Column Repair StrategiesRepair StrategiesFRP Column FRP Column Repair StrategiesRepair Strategies Surface preparation optionsSurface preparation options

Remove unsound concrete to a depth of no less than 25 Remove unsound concrete to a depth of no less than 25 ppmm from the rear most of reinforcement to sound mm from the rear most of reinforcement to sound concreteconcrete.. Cost $750/sq mCost $750/sq m Cost $750/sq. mCost $750/sq. m

Remove the unsound concrete to rebar depthRemove the unsound concrete to rebar depth Cost $270/sq. mCost $270/sq. m

No removal of concrete. Just No removal of concrete. Just smooth smooth it.it. Minimal Minimal costcost

E ti t d t f FRP i (2002)E ti t d t f FRP i (2002) Estimated cost of FRP repair (2002)Estimated cost of FRP repair (2002) $125/sq. m for E$125/sq. m for E--GlassGlass

$175/sq m for Carbon$175/sq m for Carbon $175/sq. m for Carbon$175/sq. m for Carbon

Test StructureTest StructureTest StructureTest Structure

Rte 2 over Hudson River BridgeRte 2 over Hudson River BridgeRte 2 over Hudson River BridgeRte 2 over Hudson River Bridge Built in 1969Built in 1969 Eight span Eight span steel stringer bridgesteel stringer bridge 430430--m long and 23m long and 23--m widem wide Columns deteriorated (nonColumns deteriorated (non--structural)structural)

Leaking jointsLeaking joints Leaking jointsLeaking joints Repaired (Patched) in 1991 and 1992Repaired (Patched) in 1991 and 1992 Conventional repairs failed quickly. These were also Conventional repairs failed quickly. These were also p q yp q y

expensive and require considerable time, personnel, expensive and require considerable time, personnel, and moneyand money

Test StructureTest StructureTest StructureTest Structure

Test StructureTest StructureTest StructureTest Structure

Repaired in JulyRepaired in July--August 1999August 1999 FRP Wrapping in September 1999FRP Wrapping in September 1999 Done by maintenance personnelDone by maintenance personnel Instrumentation for monitoringInstrumentation for monitoring

Corrosion rateCorrosion rate HumidityHumidity TemperatureTemperature Three locations for column based potential dataThree locations for column based potential data

ResultsResultsResultsResults

Bennetts Creek BridgeBennetts Creek BridgeBennett s Creek BridgeBennett s Creek Bridge

Evaluation/Monitoring of thefirst FRP Slab Bridge in USon a FHWA-recognized Stateon a FHWA recognized StateHighway System

150

200

250

m

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0

50

100

S

t

r

a

i

n

(

m

-500 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Gage Numbers

10/1998 05/1999 04/2000 11/2000 09/2002 11/2005

Fatigue Evaluation of Fatigue Evaluation of PatroonPatroon Island BridgeIsland Bridge(Assists in making a decision on repair vs. replacement options(Assists in making a decision on repair vs. replacement options))

Evaluation of Cracked Hanger Plate Evaluation of Cracked Hanger Plate Welds of an Arch BridgeWelds of an Arch Bridge

Infrared ThermographyInfrared ThermographyInfrared ThermographyInfrared Thermography

Issues with SHM ImplementationIssues with SHM ImplementationIssues with SHM ImplementationIssues with SHM Implementation Most current methods meant for local Most current methods meant for local

NDTNDTNDTNDT Increased CostIncreased Cost

Initial, maintenance, analysisInitial, maintenance, analysis Structural environment changesStructural environment changesgg

Slow: Corrosion, general degradation, etc.Slow: Corrosion, general degradation, etc. Sudden: Impact blast etcSudden: Impact blast etcSudden: Impact, blast, etc.Sudden: Impact, blast, etc. Overloads etc., due to change in useOverloads etc., due to change in use

Long breakLong break even periodeven period Long breakLong break--even periodeven period Project vs. networkProject vs. network

Why SHCE is useful in the future?Why SHCE is useful in the future?

Change in bridge management philosophyChange in bridge management philosophyN i l d iN i l d i New materials and practicesNew materials and practices

New trend in SHCENew trend in SHCE Sensor technologiesSensor technologies Remote sensingRemote sensinggg

Cost benefit and Cost benefit and LCALCA approachesapproaches Smart structuresSmart structures Smart structuresSmart structures

Concluding RemarksConcluding RemarksConcluding RemarksConcluding Remarks

Another toolAnother tool Another toolAnother tool Use it wiselyUse it wisely Benefits (value) > costBenefits (value) > cost SHCE should be incorporated into Bridge SHCE should be incorporated into Bridge p gp g

Management Software systems such as Management Software systems such as PONTISPONTIS as a viable option.as a viable option.pp

QuestionsQuestionsQuestionsQuestions

11 What should drive the decision to useWhat should drive the decision to use1.1. What should drive the decision to use What should drive the decision to use SHM?SHM?

22 Wh t th t f i k?Wh t th t f i k?2.2. What are the components of risk?What are the components of risk?3.3. What is a passive sensor?What is a passive sensor?4.4. Which failure is easier to monitor using Which failure is easier to monitor using

SHM: ductile or brittle? Why?SHM: ductile or brittle? Why?yy5.5. Is there any reason to use SHM where Is there any reason to use SHM where

costs are greater than benefits?costs are greater than benefits?costs are greater than benefits?costs are greater than benefits?

AnswersAnswersAnswersAnswers

11 DecisionDecision makingmaking1.1. DecisionDecision--makingmaking2.2. Probability of failure and consequencesProbability of failure and consequences3.3. Does not require power etc. and can be Does not require power etc. and can be

probed as neededprobed as needed4.4. Ductile. Large deformations and longer Ductile. Large deformations and longer

response timesresponse timespp5.5. Research and development, proof of Research and development, proof of

conceptconceptconceptconcept