Presented by Margaret G. Brier, Ozzie Gooen, Andrew Ho, and Sara Sholes May 6, 2010

1. Presented by Margaret G. Brier, Ozzie Gooen, Andrew Ho, and Sara Sholes May 6, 2010 E80 Field ExperienceNDE and System Identification ofa Concrete Bridge

3. Table of Contents • Introduction • Background • Statement of Work • Set-up • Bridge Description & Configuration • Measurement Layout • Instrumentation • Accelerometer • Matlab GUI • NI DAQ • Hammer and Tips • Hammer Tip Selection • Testing Procedure • Parameters • Impulse Triggered • Number of hits/trials • Data Processing • Sample Data • Description of Analysis Procedure • PreFreq80 Data Processing • Freq80 • Interpretation of Results • Response Frequencies and Shapes • Damping • Technical Highlight • Summary • Appendixes: • Appendix A: FRF Plots at all Locations • Appendix B: FRF Effects of Detrending and Windowing Data • Appendix C: Heavy End Detrending

4. Background Studies in the 1990s indicated the need to retrofit the nation’s bridges. Non-destructive testing was implemented to systematically analyze these structures. We have studied the Mountain Avenue Bridge, over the California 210 Highway. The Mountain Avenue Bridge was designed in 1998 by the California Department of Transportation.

5. Statement of Work From this analysis, we plan on identifying the: Fundamental Resonance Fundamental Response Shape Damping estimate The fundamental resonance frequency is the frequency at which the bridge will oscillate at its maximum magnitude. At the first resonant frequency, the bridge’s response shape will be in the form of one period of a sine wave. If possible, we were to investigate the response shapes at higher modes. After determining the fundamental resonance, a damping estimate for the fundamental response can be found.

6. Bridge Description and Configuration

7. Bridge Description and Configuration

8. Measurement Layout To take data along the length of the bridge, we placed two accelerometers as seen below and took ten sets of impact data at Locations 0 to 9 as shown. 0 1 2 3 4 5 6 7 8 9 Accel 1 Accel 2

9. Measurement Layout (con’t) When choosing how many locations to impact, it was necessary to consider both quality of data and time constraints. We took as many data points as possible in the available time. No data was taken when cars, pedestrians, or bicycles were moving across the bridge. This restricted the quantity of data. In addition to the ten evenly spaced locations, data was also taken at the center of the bridge, on lamposts, around a joint, and on the guardrail.

10. Measurement Layout (con’t) 1.0’ 0 • Testing performed solely on East walkway • Accelerometers 1 ft from railing • Impact testing also 1 ft from railing, along line of accelerometers N 1 Noacc W E 2 S 3 30.6’ 4 55.1’ 5 275.6’ 6 7 Soacc 8 9 4.6’

11. Instrumentation The following were used to take data: Accelerometer (Dytran Model 3191A1) Signal Conditioners/Filters Matlab based GUI with National Instruments DAQ Center Calibrated Impact Hammer (Dytran Model 5802A) Hammer Tips (Lixie 200)

12. Instrumentation-Accelerometer [2] http://www.dytran.com/products/3191A.pdf

13. Instrumentation-Signal Conditioner/Filter [3] http://www.dytran.com/products/4105.pdf

14. Instrumentation - Matlab GUI Force Impulse Channel Accel 1 Channel Accel 2 Channel 3 Channels Combined Bonus Channel Parameter Settings

15. Instrumentation - NI DAQ [4] http://www.ni.com/pdf/manuals/321183a.pdf

16. Instrumentation - Hammer and Tips [1] http://www.dytran.com/products/5802A.pdf [2] http://www4.hmc.edu/engineering/eng80/lects/E80FE_FSSID_2010.pdf

17. Hammer Tip Selection The Ideal tip should provide: • pure impulse force • minimal rise time • zero force before and after impulse

18. Hammer Tip Selection

19. Hammer Tip Selection

20. Hammer Tip Selection Red tip Orange tip Black tip Green tip

21. Hammer Tip Selection

22. Tip Testing Conclusions • Both frequency domain and time domain data show that the green tip was the best choice. • Our hammer tip analysis would have been more complete if the sampling resolution were higher.

23. Table of Contents • Background • Statement of Work • Bridge Description & Configuration • Measurement Layout • Instrumentation • Accelerometer • Matlab GUI • NI DAQ • Hammer and Tips • Hammer Tip Selection • Testing Procedure • Parameters • Impulse Triggered • Number of hits/trials • Data Processing • Sample Data • Description of Analysis Procedure • PreFreq80 Data Processing • Freq80 • Interpretation of Results • Damping • Technical Highlight • Summary • Appendix A: FRF Plots at all Locations • Appendix B: FRF Effects of Detrending and Windowing Data • Appendix C: Heavy End Detrending

24. Testing Procedures Figure. A Block Diagram of the Impact Testing Procedure

25. Parameters • 4000 samples per second • 8 seconds total • .2 seconds pre-trigger • 7.8 seconds post-trigger • Trigger level = 1V above noise level • 25 Hz Filter

26. Impulse Trigger Method • Parameters • Impulse Triggered • Number of hits/trials • Repeatability • Saturation Location 1, Trial 0, 4/20/10

27. Number of hits/trials 3 hits processing

28. Number of hits/trials 4 hits processing

29. Number of hits/trials 5 hits processing

30. Number of hits/trials 6 hits processing

31. Table of Contents • Background • Statement of Work • Bridge Description & Configuration • Measurement Layout • Instrumentation • Accelerometer • Matlab GUI • NI DAQ • Hammer and Tips • Hammer Tip Selection • Testing Procedure • Parameters • Impulse Triggered • Number of hits/trials • Data Processing • Sample Data • Description of Analysis Procedure • PreFreq80 Data Processing • Freq80 • Interpretation of Results • Damping • Technical Highlight • Summary • Appendix A: FRF Plots at all Locations • Appendix B: FRF Effects of Detrending and Windowing Data • Appendix C: Heavy End Detrending

32. Sample Data Location 1, Trial 0 • Hammer Gain x1 • Accelerometer Gain x10 • 25 Hz Cutoff

33. Description of Analysis Procedure • Windowing • Detrending • Removing Noise Before Processing After Processing

34. PreFreq80 Data Processing Before Processing After Processing Force Impulse

35. PreFreq80 Data Processing • Detrending removes the best fit line Force Impulse

36. PreFreq80 Data Processing • Windowing removes remaining noise Force Impulse

37. PreFreq80 Data Processing • Close up on noise windowing Force Impulse

38. PreFreq80 Data Processing Acceleration Processing Before Processing After Processing

39. PreFreq80 Data Processing Acceleration Processing Detrend post-transient post trigger Shorten pre-trigger (.2 seconds to .01seconds) Matlab detrend function with breakpoints in transient region [200 1056 1250 1320:3000:16384] Subtract mean from pre-trigger

40. Freq80 • Freq80 yields , an estimate of • Assumes no noise • Used block averaging • Also Assumes periodicity • Needed to apply an exponential window • Works best with minimal pre-trigger data.

41. Freq80 • Freq80 applied an exponential window using τ = .899 for a desired 1% of original signal by T = 4.096 seconds.

42. Table of Contents • Background • Statement of Work • Bridge Description & Configuration • Measurement Layout • Instrumentation • Accelerometer • Matlab GUI • NI DAQ • Hammer and Tips • Hammer Tip Selection • Testing Procedure • Parameters • Impulse Triggered • Number of hits/trials • Data Processing • Sample Data • Description of Analysis Procedure • PreFreq80 Data Processing • Freq80 • Interpretation of Results • Damping • Technical Highlight • Summary • Appendix A: FRF Plots at all Locations • Appendix B: FRF Effects of Detrending and Windowing Data • Appendix C: Heavy End Detrending

43. Data Interpretation Sample Gain, Phase, and Coherence Data, after Freq80 (Location 1).

44. Bridge Characteristics Close-up of Gain with Coherence (Location 1).