October 22, 2014 Monitoring the Health of Structures
October 22, 2014 Monitoring the Health of Structures for Quantifying and Achieving Resilience for Natural Hazards Bilal M. Ayyub and Yunfeng Zhang Department of Civil & Environmental Engineering University of Maryland, College Park [email protected] and [email protected] Motivation After natural hazardous events, engineers are usually faced with many competing priorities in making safety and occupancy decisions about large inventories of building and bridge assets, which could be more effectively managed through automated inspection and computerized condition assessment. Fractured EBF in Pacific Tower, from Bruneau et al. 2012 2 EBF Building Damage in the 2011 M6.3 Christchurch, New Zealand Earthquake Club Tower building, completed in 2009. estimates of the peak inelastic demand in the active link were made through visible assessment of the active link yielded web
metal. Paint flaking of partially hidden EBF link & global view of 3 EBF braces obstructed by various utility runs. [Photos by M. Bruneau and C Clifton] CBF Building Damage in the 1994 M6.7 Northridge Earthquake (California) The building remained plumb following the earthquake. The initial assessment of the structure by the owner's representative was that the structure had not sustained much damage (only one window had been broken). Only after the dry wall was removed, the extent of damage was revealed. 4 Photos from Sabelli 2013 and Trembaly 1995 Clearly, ability of rapid structural condition assessment especially for many hidden locations after major hazardous events reduces the time to recovery and increases the resilience in disaster recovery Rapid condition assessment
Performance (Q) 100% 50% Conventional inspection approach Q0h1 Q0h2 0 tf tf+Tr1 tf+Tr2 5 Time Resilience Metrics (Ayyub 2013) A Poisson process with rate l leading to an incident occurrence tf
fdt Performance as new t Failure ( F ) t fi Target Failure event definitions: f1. Brittle f2. Ductile f3. Graceful f3 f1 f2 ti Robustness, i.e., residual performance (Qr) Recovery costs Resilience ( Re ) 0 rdt
t Recovery ( R) trf Qdt Disruption duration Td Recovery duration Tr Failure duration Tf tf Not to scale ti 0 tr Estimated performance with aging effects Tr = Time to recovery Tf = Time to failure Ti = Time to incident 0 Qdt
Performance after recovery r5 r6 Recovery event definitions: r1. E. better than new r2. E. as good as new r3. E. better than old r4. E. as good as old r5. As good as old r6. Worse than old E. = Expeditiously 6 r1 r2 r3 r4 tf tr Time Indirect impacts including loss of performance Ti FT f RTr
Ti T f Tr Direct failure impacts Re > 0 Impacts valuated Measuring Performance (Ayyub 2013) Systems Buildings Other structures: Highway bridges Facilities: Water treatment plants Infrastructure: Water delivery Network: Electric power distribution Communities Performance Space availability Throughput traffic Water production capacity Water available for consumption Power delivered Economic output Quality of life (consumption) 7 Units Area per day Count per day Volume per day
Volume Power per day Dollars Dollars Resilience Metrics (Ayyub 2013) Resilience ( Re ) Ti FT f RTr Re < 1 Ti T f Tr tf tr fdt rdt t Failure ( F ) t fi Qdt ti t Recovery ( R) trf
Qdt tf The failure-profile value (F) can be considered as a measure of robustness and redundancy; whereas the recovery-profile value (R) can be considered as a measure of resourcefulness and rapidity. Definition for resilience components Measuring resilience based on its components (MCEER): Robustness as the ability of the system and system elements to withstand external shocks without significant loss of performance Redundancy as the extent to which the system and other elements satisfy and sustain functions in the event of disturbance Resourcefulness as the ability to diagnose and prioritize problems and to initiate solutions by identifying and monitoring all resources, including economic, technical, and social information Rapidity as the ability to recover and contain losses and avoid future disruptions
9 Resilience concept of functionality versus recovery time A Poisson process with rate l leading to an incident occurrence Performance as new Target Qf1 Qf0 Qf2 Failure event definitions: f1. Brittle f2. Ductile f3. Graceful f3 f1 f2 0 Performance after recovery r5 r6
Recovery event definitions: r1. E. better than new r2. E. as good as new r3. E. better than old r4. E. as good as old r5. As good as old r6. Worse than old E. = Expeditiously Robustness, i.e., residual performance (Qr) Estimated performance with aging effects Disruption duration Td Recovery duration Tr Failure duration Tf Tr = Time to recovery Tf = Time to failure Ti = Time to incident 0 r1 r2 r3 r4
Not to scale ti tf tr tr1 tr2 Time Structural health monitoring system should generate an alarm signal whenever the strain exceeds the pre-specified limit state (e.g., yielding, fracture or buckling). Strain gage 1 44 in (1.1 m) Strain gage 2 Strain gage 1 30 in (0.76 m) RFID reader
Hybrid simulation test setup for system validation of WSCA on truss structure Component Validation Test -12000 Axial Strain ( ) -10000 H9W2 H9W2-FEM Gage 1 Gage 2 -8000 H6W4 H6W4-FEM -6000 -4000 Brittle Bar Size -2000
0 0 50 100 150 200 250 Time (sec.) 300 350 H6W4 H9W2 Test #1 0.65% 1.10% Test #2
0.61% 1.02% Ave. of Test values 0.63% 1.06% 400 Design value 450 0.55% 500 1.18% Alternative test plan Data acquisitio n system RFID reader
BIM user interface stub column specimen with BT strain sensors Experimental Validation Test 350 300 Stress (MPa) 250 200 H6W4 H9W2 150 100 50 0 0 0.005 0.01 0.015
0.02 Axial strain 0.025 0.03 0.035 Concluding Remarks 16 Resilience metrics is defined For such seismically resilient structures with fuse members, automated wireless scanning of fuse zone for possible damages suffered during earthquakes or strong winds could be performed in a very efficient way and this practice would greatly accelerate condition assessment and thus enhance resilience through shorter and more accurate inspection. Thank you
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