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

2. SSTL APSS-SHM lab Three Stages of SHM 1.Data measurement/acquisition Sensors and data acquisition equipment 2. System identification Extracting structural features 3. Condition assessment Damage detection algorithm 123 0 0.2 0.4 0.6 0.8 1 Impulseresponse Transferfunction Damageindex

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

4. SSTL APSS-SHM lab Vibration-based SHM Algorithms Natural frequency changes Mode shapes Modal strain energy Flexibility matrix 0102030405060708090100 -4 -3 -2 0 1 2 3 4 Time (sec) Acceleration 020406080100120140160180200 10 -9 10 -8 10 -7 10 -6 10 -5 10 -4 Freq (Hz) Freq response function

5. SSTL APSS-SHM lab 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 Datameasurements Calculation of DLVs NormalizedAccumulated Stress (NAS) Undamaged &damaged Numerical Model Structuralanalysis SVD of flexibility change matrix NormalizationSummation Damage indicator

6. SSTL APSS-SHM lab Example Spring NAS

7. SSTL APSS-SHM lab 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

8. SSTL APSS-SHM lab Experimental Parameters Distributed computing strategy: Group 1-11 Element 8: 40% stiffness reduction Group1 2 10Group11...

9. SSTL APSS-SHM lab Lab-scale Experiments Acceleration 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 Accelerometers Signal conditioner Computer NI Chassis: SCXI 1411

10. SSTL APSS-SHM lab Results

11. SSTL APSS-SHM lab Demonstration

12. SSTL APSS-SHM lab 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.edusjang4@illinois.edu