Presented by Margaret G. Brier, Ozzie Gooen, Andrew Ho, and Sara Sholes May 6, 2010
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Transcript of Presented by Margaret G. Brier, Ozzie Gooen, Andrew Ho, and Sara Sholes May 6, 2010
E80 Field Experience Engineering DepartmentHarvey Mudd College
Presented by
Margaret G. Brier, Ozzie Gooen, Andrew Ho, and Sara Sholes
May 6, 2010
E80 Field ExperienceNDE and System Identification of
a Concrete Bridge
E80 Field Experience Engineering DepartmentHarvey Mudd College
E80 Field Experience Engineering DepartmentHarvey 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 DepartmentHarvey Mudd College
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.
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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.
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Bridge Description and Configuration
E80 Field Experience Engineering DepartmentHarvey Mudd College
Bridge Description and Configuration
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Measurement Layout
0 1 2 3 4 5 6 7 8 9
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 1 Accel 2
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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.
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Measurement Layout (con’t)
55.1’ 30.6’
275.6’
N
S
EW
1.0’
4.6’
0
1
2
3
4
5
6
7
8
9
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 DepartmentHarvey 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)
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Instrumentation-Accelerometer
[2] http://www.dytran.com/products/3191A.pdf
E80 Field Experience Engineering DepartmentHarvey Mudd College
Instrumentation-Signal Conditioner/Filter
[3] http://www.dytran.com/products/4105.pdf
E80 Field Experience Engineering DepartmentHarvey Mudd College
Instrumentation - Matlab GUI
Force Impulse Channel
Accel 1 Channel
Accel 2 Channel
3 Channels Combined
Bonus Channel
Parameter Settings
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Instrumentation - NI DAQ
[4] http://www.ni.com/pdf/manuals/321183a.pdf
E80 Field Experience Engineering DepartmentHarvey Mudd College
Instrumentation - Hammer and Tips
[1] http://www.dytran.com/products/5802A.pdf
[2] http://www4.hmc.edu/engineering/eng80/lects/E80FE_FSSID_2010.pdf
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Hammer Tip Selection
The Ideal tip should provide: pure impulse force minimal rise time zero force before and after impulse
E80 Field Experience Engineering DepartmentHarvey Mudd College
Hammer Tip Selection
E80 Field Experience Engineering DepartmentHarvey Mudd College
Hammer Tip Selection
E80 Field Experience Engineering DepartmentHarvey Mudd College
Hammer Tip Selection
Red tip
Black tip
Orange tip
Green tip
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Hammer Tip Selection
E80 Field Experience Engineering DepartmentHarvey 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 DepartmentHarvey 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 DepartmentHarvey Mudd College
Testing Procedures
Figure. A Block Diagram of the Impact Testing Procedure
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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
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Impulse Trigger Method
Location 1, Trial 0, 4/20/10
ParametersImpulse Triggered
Number of hits/trialsRepeatabilitySaturation
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Number of hits/trials3 hits processing
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Number of hits/trials4 hits processing
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Number of hits/trials5 hits processing
E80 Field Experience Engineering DepartmentHarvey Mudd College
Number of hits/trials6 hits processing
E80 Field Experience Engineering DepartmentHarvey 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
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Sample Data
• Hammer Gain x1
• Accelerometer Gain x10• 25 Hz Cutoff
Location 1, Trial 0
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Description of Analysis Procedure
Before Processing After Processing
•Windowing•Detrending•Removing Noise
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PreFreq80 Data Processing
Force Impulse
Before Processing After Processing
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PreFreq80 Data Processing
• Detrending removes the best fit line
Force Impulse
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• Windowing removes remaining noise
PreFreq80 Data Processing Force Impulse
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PreFreq80 Data Processing
• Close up on noise windowing
Force Impulse
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PreFreq80 Data ProcessingAcceleration Processing
Before Processing
AfterProcessing
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PreFreq80 Data ProcessingAcceleration 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)
[200 1056 1250 1320:3000:16384]
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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.
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Freq80
• Freq80 applied an exponential window using τ = .899 for a desired 1% of original signal by T = 4.096 seconds.
E80 Field Experience Engineering DepartmentHarvey 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
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Data InterpretationSample Gain, Phase, and Coherence Data, after Freq80 (Location 1).
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Bridge CharacteristicsClose-up of Gain with Coherence (Location 1).
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E80 Field Experience Engineering DepartmentHarvey Mudd College
E80 Field Experience Engineering DepartmentHarvey Mudd College
E80 Field Experience Engineering DepartmentHarvey Mudd College
E80 Field Experience Engineering DepartmentHarvey Mudd College
E80 Field Experience Engineering DepartmentHarvey Mudd College
E80 Field Experience Engineering DepartmentHarvey Mudd College
E80 Field Experience Engineering DepartmentHarvey Mudd College
E80 Field Experience Engineering DepartmentHarvey Mudd College
E80 Field Experience Engineering DepartmentHarvey Mudd College
E80 Field Experience Engineering DepartmentHarvey Mudd College
E80 Field Experience Engineering DepartmentHarvey 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 DepartmentHarvey Mudd College
E80 Field Experience Engineering DepartmentHarvey 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.
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GuardrailClear resonant frequencies can not be identified from the data taken from the guardrail.
E80 Field Experience Engineering DepartmentHarvey Mudd College
E80 Field Experience Engineering DepartmentHarvey 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 DepartmentHarvey Mudd College
E80 Field Experience Engineering DepartmentHarvey Mudd College
Bad Resonance Shapes
• 8.8 Hz• No clear resonance shape
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E80 Field Experience Engineering DepartmentHarvey Mudd College
Bad Resonance Shapes
• 12.2 Hz• No clear resonance shape
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E80 Field Experience Engineering DepartmentHarvey Mudd College
Damping Estimate
Δ F
•Bandwidth appears at 3dB below resonant peak.
•Use quality factor Q relation.
•Q = fr / Δ F
•Q > ½ = underdamped
•ζ = 1/2Q = Δ F/ 2 fr
•Combined averages from all visible peaks.
•Damping Estimate ζ = .05
E80 Field Experience Engineering DepartmentHarvey Mudd College
E80 Field Experience Engineering DepartmentHarvey 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 2nd order system or characterize a frequency response function. Instead, we used the Reynold’s 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)
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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
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Summary
The experimentally determined fundamental resonant frequency of the bridge is 5.1 Hz.
The damping ratio is ζ=.05.
E80 Field Experience Engineering DepartmentHarvey 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
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(more) Questions?
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Appendices
Appendix A: FRF Plots at all Locations Appendix B: FRF Effects of Detrending
and Windowing Data
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Appendix A – FRF Plots at all Locations
Location 0
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Appendix A – FRF Plots at all Locations
Location 1
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Appendix A – FRF Plots at all Locations
Location 2
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Appendix A – FRF Plots at all Locations
Location 3
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Appendix A – FRF Plots at all Locations
Location 4
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Appendix A – FRF Plots at all Locations
Location 5
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Appendix A – FRF Plots at all Locations
Location 6
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Appendix A – FRF Plots at all Locations
Location 7
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Appendix A – FRF Plots at all Locations
Location 8
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Appendix A – FRF Plots at all Locations
Location 9
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Appendix A – FRF Plots at all Locations
Location Pier Support
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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 16384. (unprocessed)
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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 16384. (unprocessed)
E80 Field Experience Engineering DepartmentHarvey 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 16384. (unprocessed)•Force has been detrended, but not windowed
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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 16384. (unprocessed)•Force has been detrended, but not windowed
Fully Processed Current Modifications
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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 16384. (unprocessed)•Force has been detrended, and windowed to remove noise
E80 Field Experience Engineering DepartmentHarvey 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 16384. (unprocessed)•Force has been detrended, and windowed to remove noise.
Fully Processed Current Modifications
E80 Field Experience Engineering DepartmentHarvey 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 16384. (unprocessed)•Force has noise removed, but not detrended
E80 Field Experience Engineering DepartmentHarvey 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 16384. (unprocessed)•Force has noise removed, but not detrended
Fully Processed Current Modifications
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Appendix B – FRF effects of Detrending and Windowing Data
Recap: Modifications to Force Input
No detrend/window Detrend only
E80 Field Experience Engineering DepartmentHarvey Mudd College
Appendix B – FRF effects of Detrending and Windowing Data
Recap: Modifications to Force Input
Detrend + WindowWindowing only
E80 Field Experience Engineering DepartmentHarvey 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
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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
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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 16384. (unprocessed)•Force has been detrended/ windowed to remove noise•Pre-trigger time has been reduced to .01 seconds.
E80 Field Experience Engineering DepartmentHarvey 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 16384. (unprocessed)•Force has been detrended/ windowed to remove noise•Pre-trigger time has been reduced to .01 seconds.
E80 Field Experience Engineering DepartmentHarvey Mudd College
Appendix B – FRF effects of Detrending and Windowing Data
Modifications:•Data sets have been reduced to block size 16384. (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 DepartmentHarvey 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 16384. (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 DepartmentHarvey 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 16384. (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
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Appendix B – FRF effects of Detrending and Windowing Data
Location 1, Trial 0, noacc
Exponential region
Transient Region
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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 16384. (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
[200 1056 1250 1320:3000:16384]
3 points in transient, every 3000 in exponential
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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 16384. (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
[0 813 865 941 1026 1122 1227 1280 1320:1000:16384]
Heavy end of detrending
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Actually causes peaks to show up in south accel, at the cost of coherence[0 813 865 941 1026 1122 1227 1280 1320:1000:16384]
Heavy end of detrending
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Compare with actual data used in total processing
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Location 0
Appendix C- Heavy End Detrending
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Location 1
Appendix C- Heavy End Detrending
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Location 2
Appendix C- Heavy End Detrending
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Location 3
Appendix C- Heavy End Detrending
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Location 4
Appendix C- Heavy End Detrending
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Location 5
Appendix C- Heavy End Detrending
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Location 6
Appendix C- Heavy End Detrending
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Location 7
Appendix C- Heavy End Detrending
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Location 8
Appendix C- Heavy End Detrending
E80 Field Experience Engineering DepartmentHarvey Mudd College
Location 9
Appendix C- Heavy End Detrending