E80 Field Experience Engineering Department Harvey Mudd College Presented by Margaret G. Brier, Ozzie Gooen, Andrew Ho, and Sara Sholes May 6, 2010 E80 Field Experience NDE and System Identification of a Concrete Bridge E80 Field Experience Engineering Department Harvey Mudd College E80 Field Experience Engineering Department Harvey Mudd College 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 E80 Field Experience Engineering Department Harvey Mudd College Background Studies in the 1990s indicated the need to retrofit the nations 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. E80 Field Experience Engineering Department Harvey Mudd College 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 bridges 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. E80 Field Experience Engineering Department Harvey Mudd College Bridge Description and Configuration E80 Field Experience Engineering Department Harvey Mudd College Bridge Description and Configuration E80 Field Experience Engineering Department Harvey Mudd College 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. Accel 1Accel 2 E80 Field Experience Engineering Department Harvey Mudd College Measurement Layout (cont) 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. E80 Field Experience Engineering Department Harvey Mudd College Measurement Layout (cont) 55.1 30.6 275.6 N S EW 1.0 4.6 Noacc Soacc Testing performed solely on East walkway Accelerometers 1 ft from railing Impact testing also 1 ft from railing, along line of accelerometers E80 Field Experience Engineering Department Harvey Mudd College 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) E80 Field Experience Engineering Department Harvey Mudd College Instrumentation-Accelerometer [2] E80 Field Experience Engineering Department Harvey Mudd College Instrumentation-Signal Conditioner/Filter [3] E80 Field Experience Engineering Department Harvey Mudd College Instrumentation - Matlab GUI Force Impulse Channel Accel 1 Channel Accel 2 Channel 3 Channels Combined Bonus Channel Parameter Settings E80 Field Experience Engineering Department Harvey Mudd College Instrumentation - NI DAQ [4] E80 Field Experience Engineering Department Harvey Mudd College Instrumentation - Hammer and Tips [1][2] E80 Field Experience Engineering Department Harvey Mudd College Hammer Tip Selection The Ideal tip should provide: pure impulse force minimal rise time zero force before and after impulse E80 Field Experience Engineering Department Harvey Mudd College Hammer Tip Selection E80 Field Experience Engineering Department Harvey Mudd College Hammer Tip Selection E80 Field Experience Engineering Department Harvey Mudd College Hammer Tip Selection Red tip Black tip Orange tip Green tip E80 Field Experience Engineering Department Harvey Mudd College Hammer Tip Selection E80 Field Experience Engineering Department Harvey Mudd College 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. E80 Field Experience Engineering Department Harvey Mudd College 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 E80 Field Experience Engineering Department Harvey Mudd College Testing Procedures Figure. A Block Diagram of the Impact Testing Procedure E80 Field Experience Engineering Department Harvey Mudd College 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 E80 Field Experience Engineering Department Harvey Mudd College Impulse Trigger Method Location 1, Trial 0, 4/20/10 Parameters Impulse Triggered Number of hits/trials Repeatability Saturation E80 Field Experience Engineering Department Harvey Mudd College Number of hits/trials 3 hits processing E80 Field Experience Engineering Department Harvey Mudd College Number of hits/trials 4 hits processing E80 Field Experience Engineering Department Harvey Mudd College Number of hits/trials 5 hits processing E80 Field Experience Engineering Department Harvey Mudd College Number of hits/trials 6 hits processing E80 Field Experience Engineering Department Harvey Mudd College 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 E80 Field Experience Engineering Department Harvey Mudd College Sample Data Hammer Gain x1 Accelerometer Gain x10 25 Hz Cutoff Location 1, Trial 0 E80 Field Experience Engineering Department Harvey Mudd College Description of Analysis Procedure Before ProcessingAfter Processing Windowing Detrending Removing Noise E80 Field Experience Engineering Department Harvey Mudd College PreFreq80 Data Processing Force Impulse Before ProcessingAfter Processing E80 Field Experience Engineering Department Harvey Mudd College PreFreq80 Data Processing Detrending removes the best fit line Force Impulse E80 Field Experience Engineering Department Harvey Mudd College Windowing removes remaining noise PreFreq80 Data Processing Force Impulse E80 Field Experience Engineering Department Harvey Mudd College PreFreq80 Data Processing Close up on noise windowing Force Impulse E80 Field Experience Engineering Department Harvey Mudd College PreFreq80 Data Processing Acceleration Processing Before Processing After Processing E80 Field Experience Engineering Department Harvey Mudd College PreFreq80 Data Processing Acceleration Processing Subtract mean from pre-trigger Matlab detrend function with breakpoints in transient region Detrend post-transient post trigger Shorten pre-trigger (.2 seconds to.01seconds) [ :3000:16384] E80 Field Experience Engineering Department Harvey Mudd College 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. E80 Field Experience Engineering Department Harvey Mudd College Freq80 Freq80 applied an exponential window using =.899 for a desired 1% of original signal by T = seconds. E80 Field Experience Engineering Department Harvey Mudd College 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 E80 Field Experience Engineering Department Harvey Mudd College Data Interpretation Sample Gain, Phase, and Coherence Data, after Freq80 (Location 1). E80 Field Experience Engineering Department Harvey Mudd College Bridge Characteristics Close-up of Gain with Coherence (Location 1). E80 Field Experience Engineering Department Harvey Mudd College E80 Field Experience Engineering Department Harvey Mudd College E80 Field Experience Engineering Department Harvey Mudd College E80 Field Experience Engineering Department Harvey Mudd College E80 Field Experience Engineering Department Harvey Mudd College E80 Field Experience Engineering Department Harvey Mudd College E80 Field Experience Engineering Department Harvey Mudd College E80 Field Experience Engineering Department Harvey Mudd College E80 Field Experience Engineering Department Harvey Mudd College E80 Field Experience Engineering Department Harvey Mudd College E80 Field Experience Engineering Department Harvey Mudd College E80 Field Experience Engineering Department Harvey Mudd College Lampposts When analyzing lamppost data, we see a peak at 3.4 Hz. 3.4 Hz peaks can be seen throughout the full bridge data. E80 Field Experience Engineering Department Harvey Mudd College E80 Field Experience Engineering Department Harvey Mudd College Bridge Joint These are examples of data from impacting around the joint between the bridge and the ground on the other side. There are no discernable resonances from the data around the joint. E80 Field Experience Engineering Department Harvey Mudd College Guardrail Clear resonant frequencies can not be identified from the data taken from the guardrail. E80 Field Experience Engineering Department Harvey Mudd College E80 Field Experience Engineering Department Harvey Mudd College Resonance Shapes Resonance shape at 5.1 Hz. We can see from this video that at 5.1 Hz the resonance shape resembles what we expect for the fundamental resonance. E80 Field Experience Engineering Department Harvey Mudd College E80 Field Experience Engineering Department Harvey Mudd College Bad Resonance Shapes 8.8 Hz No clear resonance shape E80 Field Experience Engineering Department Harvey Mudd College E80 Field Experience Engineering Department Harvey Mudd College Bad Resonance Shapes 12.2 Hz No clear resonance shape E80 Field Experience Engineering Department Harvey Mudd College E80 Field Experience Engineering Department Harvey Mudd College Damping Estimate F Bandwidth appears at 3dB below resonant peak. Use quality factor Q relation. Q = fr / F Q > = underdamped = 1/2Q = F/ 2 f r Combined averages from all visible peaks. Damping Estimate =.05 E80 Field Experience Engineering Department Harvey Mudd College E80 Field Experience Engineering Department Harvey Mudd College Technical Highlight CEMACZ: We compared how a theoretically predicted frequency response function compared with the experimental FRF for a step and sinusoidal input. Dynamic Beam Modeling: When theoretically modeling the system, we considered the response as a function of location (through static deflection) and the response as a function of time (through energy considerations)) separately, and then combined to determine the overall frequency response function. The theoretical input was an impulse. Dynamic Beam Testing: We experimentally determined the frequency response function of the two distinct elements of the system (the beam and the TVA) based on the input and output signals, and from these responses designed the system to obtain desired overall frequency response. Bucket Lab: We had a rough theoretical model for system, but did not know direct effect of various parameters. We determined some the parameters based on the log decrement displacement for a step input. Wind Tunnel: In the wind tunnel, we did not treat the system as a 2 nd order system or characterize a frequency response function. Instead, we used the Reynolds number relation to design a system with the desired output. Static Motor: We characterized the system based on the input and output data. The input data to this system was random vibration (which in the frequency domain is like a Gaussian distribution) E80 Field Experience Engineering Department Harvey Mudd College Technical Highlight Generally, want to be able to understand the response of a system (might want to control damping, resonant frequency, bandwidth, etc) In E80, we explored various methods to characterize the response of a system E80 Field Experience Engineering Department Harvey Mudd College Summary The experimentally determined fundamental resonant frequency of the bridge is 5.1 Hz. The damping ratio is =.05. E80 Field Experience Engineering Department Harvey Mudd College Thanks The E80 Team: Professors Zee Duron, Nancy Lape, Liz Orwin, and Qimin Yang The Section 2 E80 Proctors: Ariel Berman, Elizabeth Ellis, and Allie Russell Willie Drake and Sam Abdelmuati for preparing and testing the instrumentation E80 Field Experience Engineering Department Harvey Mudd College (more) Questions? E80 Field Experience Engineering Department Harvey Mudd College Appendices Appendix A: FRF Plots at all Locations Appendix B: FRF Effects of Detrending and Windowing Data E80 Field Experience Engineering Department Harvey Mudd College Appendix A FRF Plots at all Locations Location 0 E80 Field Experience Engineering Department Harvey Mudd College Appendix A FRF Plots at all Locations Location 1 E80 Field Experience Engineering Department Harvey Mudd College Appendix A FRF Plots at all Locations Location 2 E80 Field Experience Engineering Department Harvey Mudd College Appendix A FRF Plots at all Locations Location 3 E80 Field Experience Engineering Department Harvey Mudd College Appendix A FRF Plots at all Locations Location 4 E80 Field Experience Engineering Department Harvey Mudd College Appendix A FRF Plots at all Locations Location 5 E80 Field Experience Engineering Department Harvey Mudd College Appendix A FRF Plots at all Locations Location 6 E80 Field Experience Engineering Department Harvey Mudd College Appendix A FRF Plots at all Locations Location 7 E80 Field Experience Engineering Department Harvey Mudd College Appendix A FRF Plots at all Locations Location 8 E80 Field Experience Engineering Department Harvey Mudd College Appendix A FRF Plots at all Locations Location 9 E80 Field Experience Engineering Department Harvey Mudd College Appendix A FRF Plots at all Locations Location Pier Support E80 Field Experience Engineering Department Harvey Mudd College Appendix B FRF effects of Detrending and Windowing Data Location 1, Trial 0, Test (a), noacc Modifications: Data sets have been reduced to block size (unprocessed) E80 Field Experience Engineering Department Harvey Mudd College Appendix B FRF effects of Detrending and Windowing Data Location 1, Trial 0, Test (a), noacc Modifications: Data sets have been reduced to block size (unprocessed) E80 Field Experience Engineering Department Harvey Mudd College Appendix B FRF effects of Detrending and Windowing Data Location 1, Trial 0, Test (b), noacc Modifications: Data sets have been reduced to block size (unprocessed) Force has been detrended, but not windowed E80 Field Experience Engineering Department Harvey Mudd College Appendix B FRF effects of Detrending and Windowing Data Location 1, Trial 0, Test (b), noacc Modifications: Data sets have been reduced to block size (unprocessed) Force has been detrended, but not windowed Fully Processed Current Modifications E80 Field Experience Engineering Department Harvey Mudd College Appendix B FRF effects of Detrending and Windowing Data Location 1, Trial 0, Test (c), noacc Modifications: Data sets have been reduced to block size (unprocessed) Force has been detrended, and windowed to remove noise E80 Field Experience Engineering Department Harvey Mudd College Appendix B FRF effects of Detrending and Windowing Data Location 1, Trial 0, Test (c), noacc Modifications: Data sets have been reduced to block size (unprocessed) Force has been detrended, and windowed to remove noise. Fully Processed Current Modifications E80 Field Experience Engineering Department Harvey Mudd College Appendix B FRF effects of Detrending and Windowing Data Location 1, Trial 0, Test (d), noacc Modifications: Data sets have been reduced to block size (unprocessed) Force has noise removed, but not detrended E80 Field Experience Engineering Department Harvey Mudd College Appendix B FRF effects of Detrending and Windowing Data Location 1, Trial 0, Test (d), noacc Modifications: Data sets have been reduced to block size (unprocessed) Force has noise removed, but not detrended Fully Processed Current Modifications E80 Field Experience Engineering Department Harvey Mudd College Appendix B FRF effects of Detrending and Windowing Data Recap: Modifications to Force Input No detrend/windowDetrend only E80 Field Experience Engineering Department Harvey Mudd College Appendix B FRF effects of Detrending and Windowing Data Recap: Modifications to Force Input Detrend + Window Windowing only E80 Field Experience Engineering Department Harvey Mudd College Appendix B FRF effects of Detrending and Windowing Data Recap: Modifications to Force Input Comments: Detrending only: Increases gain of FRF, introduces low frequency content Windowing only: Little to no change Detrend + Window: Reflects changes from both above Next: Reducing the pretrigger to.01 seconds rather than.2 seconds Better fits exponential windowing in Freq80 E80 Field Experience Engineering Department Harvey Mudd College Appendix B FRF effects of Detrending and Windowing Data Location 1, Trial 0, Test (e), noacc Modifications: From Test(d), keep force detrended and windowed Reduce pretrigger to.01 seconds E80 Field Experience Engineering Department Harvey Mudd College Appendix B FRF effects of Detrending and Windowing Data Location 1, Trial 0, Test (e), noacc Test(d).2 seconds pretrigger Test(e).01 seconds pretrigger Modifications: Data sets have been reduced to block size (unprocessed) Force has been detrended/ windowed to remove noise Pre-trigger time has been reduced to.01 seconds. E80 Field Experience Engineering Department Harvey Mudd College Appendix B FRF effects of Detrending and Windowing Data Location 1, Trial 0, noacc Test(f).1 seconds pretrigger Test(g).15 seconds pretrigger Modifications: Data sets have been reduced to block size (unprocessed) Force has been detrended/ windowed to remove noise Pre-trigger time has been reduced to.01 seconds. E80 Field Experience Engineering Department Harvey Mudd College Appendix B FRF effects of Detrending and Windowing Data Modifications: Data sets have been reduced to block size (unprocessed) Force has been detrended/ windowed to remove noise Pre-trigger time has been reduced to.01 seconds. Recap : Reducing Pre-trigger Time Comments: After detrending/windowing the force input, reducing the pre-trigger time removes low frequency content, and increases visibility of several peaks in the frequency spectrum. E80 Field Experience Engineering Department Harvey Mudd College Appendix B FRF effects of Detrending and Windowing Data Location 1, Trial 0, Test (h), noacc Modifications: Data sets have been reduced to block size (unprocessed) Force has been detrended and windowed to remove noise Pre-trigger has been reduced to.1s Pre-trigger acceleration response detrended E80 Field Experience Engineering Department Harvey Mudd College Appendix B FRF effects of Detrending and Windowing Data Location 1, Trial 0, Test (h), noacc Modifications: Data sets have been reduced to block size (unprocessed) Force has been detrended and windowed to remove noise Pre-trigger has been reduced to.1s Pre-trigger acceleration response detrended Fully Processed Current Modifications E80 Field Experience Engineering Department Harvey Mudd College Appendix B FRF effects of Detrending and Windowing Data Location 1, Trial 0, noacc Exponential region Transient Region E80 Field Experience Engineering Department Harvey Mudd College Appendix B FRF Effects of Detrending and Windowing Data Location 1, Trial 0, Test(i) noacc Modifications: Data sets have been reduced to block size (unprocessed) Force has been detrended and windowed to remove noise Pre-trigger has been reduced to.1s Pre-trigger acceleration response detrended Testing various breakpoints to detrend transient and exponential portions of acceleration response [ :3000:16384] 3 points in transient, every 3000 in exponential E80 Field Experience Engineering Department Harvey Mudd College Appendix B FRF effects of Detrending and Windowing Data Location 1, Trial 0, Test(i) noacc Modifications: Data sets have been reduced to block size (unprocessed) Force has been detrended and windowed to remove noise Pre-trigger has been reduced to.1s Pre-trigger acceleration response detrended Testing various breakpoints to detrend transient and exponential portions of acceleration response [ :1000:16384] Heavy end of detrending E80 Field Experience Engineering Department Harvey Mudd College Actually causes peaks to show up in south accel, at the cost of coherence [ :1000:16384] Heavy end of detrending E80 Field Experience Engineering Department Harvey Mudd College Compare with actual data used in total processing E80 Field Experience Engineering Department Harvey Mudd College Location 0 Appendix C- Heavy End Detrending E80 Field Experience Engineering Department Harvey Mudd College Location 1 Appendix C- Heavy End Detrending E80 Field Experience Engineering Department Harvey Mudd College Location 2 Appendix C- Heavy End Detrending E80 Field Experience Engineering Department Harvey Mudd College Location 3 Appendix C- Heavy End Detrending E80 Field Experience Engineering Department Harvey Mudd College Location 4 Appendix C- Heavy End Detrending E80 Field Experience Engineering Department Harvey Mudd College Location 5 Appendix C- Heavy End Detrending E80 Field Experience Engineering Department Harvey Mudd College Location 6 Appendix C- Heavy End Detrending E80 Field Experience Engineering Department Harvey Mudd College Location 7 Appendix C- Heavy End Detrending E80 Field Experience Engineering Department Harvey Mudd College Location 8 Appendix C- Heavy End Detrending E80 Field Experience Engineering Department Harvey Mudd College Location 9 Appendix C- Heavy End Detrending