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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. Table of Contents. Introduction Background Statement of Work Set-up Bridge Description & Configuration Measurement Layout

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presented by margaret g brier ozzie gooen andrew ho and sara sholes may 6 2010
Presented by

Margaret G. Brier, Ozzie Gooen, Andrew Ho, and Sara Sholes

May 6, 2010

E80 Field ExperienceNDE and System Identification ofa Concrete Bridge

table of contents
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
background
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.

statement of work
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.

measurement layout
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

measurement layout con t
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.

measurement layout con t1
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’

instrumentation
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)

instrumentation accelerometer
Instrumentation-Accelerometer

[2] http://www.dytran.com/products/3191A.pdf

instrumentation signal conditioner filter
Instrumentation-Signal Conditioner/Filter

[3] http://www.dytran.com/products/4105.pdf

instrumentation matlab gui
Instrumentation - Matlab GUI

Force Impulse Channel

Accel 1 Channel

Accel 2 Channel

3 Channels Combined

Bonus Channel

Parameter Settings

instrumentation ni daq
Instrumentation - NI DAQ

[4] http://www.ni.com/pdf/manuals/321183a.pdf

instrumentation hammer and tips
Instrumentation - Hammer and Tips

[1] http://www.dytran.com/products/5802A.pdf

[2] http://www4.hmc.edu/engineering/eng80/lects/E80FE_FSSID_2010.pdf

hammer tip selection
Hammer Tip Selection

The Ideal tip should provide:

  • pure impulse force
  • minimal rise time
  • zero force before and after impulse
hammer tip selection3
Hammer Tip Selection

Red tip

Orange tip

Black tip

Green tip

tip testing conclusions
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.
table of contents1
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
testing procedures
Testing Procedures

Figure. A Block Diagram of the Impact Testing Procedure

parameters
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
impulse trigger method
Impulse Trigger Method
    • Parameters
  • Impulse Triggered
    • Number of hits/trials
    • Repeatability
    • Saturation

Location 1, Trial 0, 4/20/10

number of hits trials
Number of hits/trials

3 hits processing

number of hits trials1
Number of hits/trials

4 hits processing

number of hits trials2
Number of hits/trials

5 hits processing

number of hits trials3
Number of hits/trials

6 hits processing

table of contents2
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
sample data
Sample Data

Location 1, Trial 0

  • Hammer Gain x1
  • Accelerometer Gain x10
  • 25 Hz Cutoff
description of analysis procedure
Description of Analysis Procedure
  • Windowing
  • Detrending
  • Removing Noise

Before Processing

After Processing

prefreq80 data processing
PreFreq80 Data Processing

Before Processing

After Processing

Force Impulse

prefreq80 data processing1
PreFreq80 Data Processing
  • Detrending removes the best fit line

Force Impulse

prefreq80 data processing2
PreFreq80 Data Processing
  • Windowing removes remaining noise

Force Impulse

prefreq80 data processing3
PreFreq80 Data Processing
  • Close up on noise windowing

Force Impulse

slide38

PreFreq80 Data Processing

Acceleration Processing

Before Processing

After

Processing

slide39

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

slide40

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.
slide41

Freq80

  • Freq80 applied an exponential window using τ = .899 for a desired 1% of original signal by T = 4.096 seconds.
table of contents3
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
data interpretation
Data Interpretation

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

bridge characteristics
Bridge Characteristics

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

lampposts
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.

bridge joint
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.

guardrail
Guardrail

Clear resonant frequencies can not be identified from the data taken from the guardrail.

resonance shapes
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.

bad resonance shapes
Bad Resonance Shapes
  • 8.8 Hz
  • No clear resonance shape
bad resonance shapes1
Bad Resonance Shapes
  • 12.2 Hz
  • No clear resonance shape
damping estimate
Damping Estimate
  • 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

Δ F

technical highlight
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)
technical highlight1
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
summary
Summary

The experimentally determined fundamental resonant frequency of the bridge is 5.1 Hz.

The damping ratio is ζ=.05.

thanks
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
appendices
Appendices
  • Appendix A: FRF Plots at all Locations
  • Appendix B: FRF Effects of Detrending and Windowing Data
slide86

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)
slide87

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)
slide88

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
slide89

Modifications:

  • Data sets have been reduced to block size 16384. (unprocessed)
  • Force has been detrended, but not windowed

Appendix B – FRF effects of

Detrending and Windowing Data

Location 1, Trial 0, Test (b), noacc

Current Modifications

Fully Processed

slide90

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
slide91

Modifications:

  • Data sets have been reduced to block size 16384. (unprocessed)
  • Force has been detrended, and windowed to remove noise.

Appendix B – FRF effects of

Detrending and Windowing Data

Location 1, Trial 0, Test (c), noacc

Current Modifications

Fully Processed

slide92

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
slide93

Modifications:

  • Data sets have been reduced to block size 16384. (unprocessed)
  • Force has noise removed, but not detrended

Appendix B – FRF effects of

Detrending and Windowing Data

Location 1, Trial 0, Test (d), noacc

Current Modifications

Fully Processed

slide94

Appendix B – FRF effects of

Detrending and Windowing Data

Recap: Modifications to Force Input

No detrend/window

Detrend only

slide95

Appendix B – FRF effects of

Detrending and Windowing Data

Recap: Modifications to Force Input

Windowing only

Detrend + Window

slide96

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
slide97

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
slide98

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.

Appendix B – FRF effects of

Detrending and Windowing Data

Location 1, Trial 0, Test (e), noacc

Test(e) .01 seconds pretrigger

Test(d) .2 seconds pretrigger

slide99

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.

Appendix B – FRF effects of

Detrending and Windowing Data

Location 1, Trial 0, noacc

Test(g) .15 seconds pretrigger

Test(f) .1 seconds pretrigger

slide100

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.

Appendix B – FRF effects of

Detrending and Windowing Data

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.
slide101

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
slide102

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

Appendix B – FRF effects of

Detrending and Windowing Data

Location 1, Trial 0, Test (h), noacc

Current Modifications

Fully Processed

slide103

Appendix B – FRF effects of

Detrending and Windowing Data

Location 1, Trial 0, noacc

Exponential region

Transient Region

slide104

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

Appendix B – FRF Effects of

Detrending and Windowing Data

Location 1, Trial 0, Test(i) noacc

[200 1056 1250 1320:3000:16384]

3 points in transient, every 3000 in exponential

slide105

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

Appendix B – FRF effects of

Detrending and Windowing Data

Location 1, Trial 0, Test(i) noacc

[0 813 865 941 1026 1122 1227 1280 1320:1000:16384]

Heavy end of detrending

slide106

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