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SHM: Damage Locating Vector

SHM: Damage Locating Vector. 7/9/2009 Shinae Jang. -4. 10. -5. 10. -6. 10. -7. 10. -8. 10. -9. 10. 0. 20. 40. 60. 80. 100. 120. 140. 160. 180. 200. 1. 0.8. 0.6. 0.4. 0.2. 0. 1. 2. 3. Three Stages of SHM. Impulse response. Data measurement/acquisition

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SHM: Damage Locating Vector

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  1. APSS-SHM lab SHM: Damage Locating Vector 7/9/2009 Shinae Jang

  2. -4 10 -5 10 -6 10 -7 10 -8 10 -9 10 0 20 40 60 80 100 120 140 160 180 200 1 0.8 0.6 0.4 0.2 0 1 2 3 Three Stages of SHM Impulse response • Data measurement/acquisition • Sensors and data acquisition equipment Transfer function 2. System identification Extracting structural features Damage index 3. Condition assessment Damage detection algorithm APSS-SHM lab

  3. Steel corrosion Concrete erosion Concrete cracking Crack open/closing Fatigue damage Scope of this method Damage Definition “Damage can be defined as changes introduced into a system that adversely affects its current or future performance (Sohn et al, 2003)” APSS-SHM lab

  4. 4 3 2 1 Acceleration 0 -1 -2 -3 -4 0 10 20 30 40 50 60 70 80 90 100 Time (sec) -4 10 -5 10 -6 10 Freq response function -7 10 -8 10 -9 10 0 20 40 60 80 100 120 140 160 180 200 Freq (Hz) Vibration-based SHM Algorithms • Natural frequency changes • Mode shapes • Modal strain energy • Flexibility matrix APSS-SHM lab

  5. Damage Locating Vector (DLV) Method • What is the DLV? (Bernal, 2002) • Load vectors that induce zero stress at the damaged elements • Null space of the change of the flexibility matrices before and after damage • Procedure Normalization Summation Normalized Accumulated Stress (NAS) Calculation of DLVs Structural analysis Data measurements SVD of flexibility change matrix Undamaged &damaged Numerical Model Damage indicator APSS-SHM lab

  6. NAS Spring Example APSS-SHM lab

  7. Decentralized Computing Strategy (Gao) • Damage detection by a segment of structure • Data processing in a segment • Effective and economic data processing • Complete scan using limited sensors • Reliable and robust damage detection by overlapping and comparison APSS-SHM lab

  8. Group 1 Group 2 Group 10 Group 11 16 17 18 19 20 21 22 23 24 25 26 27 28 6 10 14 18 22 26 30 34 38 42 46 50 2 5 9 13 17 21 25 29 33 37 41 45 49 53 3 7 11 15 19 23 27 31 35 39 43 47 51 1 15 1 4 8 12 16 20 24 28 32 36 40 44 48 52 2 3 4 5 6 7 8 9 10 11 12 13 14 Experimental Parameters . . . • Distributed computing strategy: Group 1-11 • Element 8: 40% stiffness reduction APSS-SHM lab

  9. Lab-scale ExperimentsAcceleration Measurement System • Wired accelerometer • PCB 353B33 • Sensitivity: 100 mV/g • Freq. range: 1 – 4,000 Hz • Measurement range: ±50 g • Signal conditioner • PCB442B104: 100x • NI AA filter module: SCXI 1141 • NI DAQ-Pad 6052 E APSS-SHM lab Accelerometers Signal conditioner Computer NI Chassis: SCXI 1411

  10. Results APSS-SHM lab

  11. Demonstration APSS-SHM lab

  12. Assignment • Download SHM lab package • Data set on the truss model • Numerical model • DLV code • http://sstl.cee.illinois.edu/apss/2009labMats.html • Assignment • Due midnight today • One report per group • Send to sjang4@illinois.edu APSS-SHM lab

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