Development of Acoustic Emission Evaluation - Auburn University

175 Pages·2011·5.39 MB·English

Research Report No. 1 for ALDOT Project 930-601

DEVELOPMENT OF ACOUSTIC EMISSION
EVALUATION METHOD FOR REPAIRED
PRESTRESSED CONCRETE BRIDGE GIRDERS

Submitted to

The Alabama Department of Transportation

Prepared by

Thomas J. Hadzor, Robert W. Barnes,
Paul H. Ziehl, Jiangong Xu, and
Anton K. Schindler

JUNE 2011
1. Report No. 2. Government Accession No. 3. Recipient Catalog No.
FHWA/ALDOT 930-601-1
4 Title and Subtitle 5 Report Date
Development of Acoustic Emission Evaluation Method for Repaired June 2011
Prestressed Concrete Bridge Girders
6 Performing Organization
Code

7. Author(s) 8 Performing
Thomas J. Hadzor, Robert W. Barnes, Paul H. Ziehl, Jiangong Xu, Organization Report No.
and Anton K. Schindler
FHWA/ALDOT 930-601-1
9 Performing Organization Name and Address 10 Work Unit No. (TRAIS)
Highway Research Center
Department of Civil Engineering
11 Contract or Grant No.
238 Harbert Engineering Center
Auburn, AL 36849
12 Sponsoring Agency Name and Address 13 Type of Report and Period
Covered
Alabama Department of Transportation
1409 Coliseum Boulevard Technical Report
Montgomery, Alabama 36130-3050 14 Sponsoring Agency Code

15 Supplementary Notes
Research performed in cooperation with the Alabama Department of Transportation
16 Abstract
Acoustic emission (AE) monitoring has proven to be a useful nondestructive testing tool in ordinary
reinforced concrete beams. Over the past decade, however, the technique has also been used to test
other concrete structures. It has been seen that acoustic emission monitoring can be used on in-service
bridges to obtain knowledge regarding the structural integrity of individual components of the structure.
In this report, acoustic emission testing was used to examine the structural integrity of four prestressed
girders in an elevated portion of the I-565 highway in Huntsville, Alabama. The testing was performed to
assess the evaluation criteria used for in-situ testing. The evaluation methods that were implemented
were the NDIS-2421 evaluation criterion, the Signal Strength Moment (SSM) Ratio evaluation, and the
Peak Cumulative Signal Strength (CSS) Ratio analysis. It was concluded that although the testing
procedure provided results efficiently, the evaluation criteria should be adjusted for the testing of in-
service prestressed concrete bridge girders.
17 Key Words 18 Distribution Statement
Acoustic emission, bridge girders, cracking, No restrictions. This document is available to the
damage, fiber-reinforced polymer, nondestructive public through the National Technical Information
testing, prestressed concrete Service, Springfield, Virginia 22161
19 Security 20 Security 21 No. of pages 22 Price
Classification (of Classification (of
162
this report) this report)
Unclassified Unclassified
_______________________
Research Report FHWA/ALDOT 930-601-1

DEVELOPMENT OF ACOUSTIC EMISSION
EVALUATION METHOD FOR REPAIRED
PRESTRESSED CONCRETE BRIDGE GIRDERS

Submitted to

The Alabama Department of Transportation

Prepared by

Thomas J. Hadzor
Robert W. Barnes
Paul H. Ziehl
Jiangong Xu
Anton K. Schindler

JUNE 2011
DISCLAIMERS

The contents of this report reflect the views of the authors, who are responsible for the facts and
the accuracy of the data presented herein. The contents do not necessarily reflect the official
views or policies of Auburn University or the Federal Highway Administration. This report does
not constitute a standard, specification, or regulation.

NOT INTENDED FOR CONSTRUCTION, BIDDING, OR PERMIT PURPOSES

Robert W. Barnes, Ph.D., P.E.
Anton K. Schindler, Ph.D., P.E.
Research Supervisors

ACKNOWLEDGEMENTS

Material contained herein was obtained in connection with a research project ALDOT 930-601,
conducted by the Auburn University Highway Research Center. Funding for the project was
provided by the Federal Highway Administration (FHWA) and the Alabama Department of
Transportation (ALDOT). The funding, cooperation, and assistance of many individuals from
each of these organizations are gratefully acknowledged. The authors would like to acknowledge
the various contributions of the following individuals:
George H. Conner, State Maintenance Engineer, ALDOT
Robert King, Structural Engineer, FHWA
Eric Christie, Bridge Maintenance Engineer, ALDOT
W. Sean Butler, First Division, ALDOT
Randall Mullins, Section Supervisor, Bridge Bureau, ALDOT
James F. Boyer, Maintenance Bureau, ALDOT
Robert A. Fulton, formerly of Maintenance Bureau, ALDOT
Mark Strickland, Specifications Engineer, ALDOT
Lyndi Blackburn, Assistant Materials and Tests Engineer, ALDOT

iv
ABSTRACT

Acoustic emission (AE) monitoring has proven to be a useful nondestructive testing tool in
ordinary reinforced concrete beams. Over the past decade, however, the technique has also
been used to test other concrete structures. It has been seen that acoustic emission monitoring
can be used on in-service bridges to obtain knowledge regarding the structural integrity of
individual components of the structure. In this report, acoustic emission testing was used to
examine the structural integrity of four prestressed girders in an elevated portion of the I-565
highway in Huntsville, Alabama. The testing was performed to assess the evaluation criteria
used for in-situ testing. The evaluation methods that were implemented were the NDIS-2421
evaluation criterion, the Signal Strength Moment (SSM) Ratio evaluation, and the Peak
Cumulative Signal Strength (CSS) Ratio analysis. It was concluded that although the testing
procedure provided results efficiently, the evaluation criteria should be adjusted for the testing of
in-service prestressed concrete bridge girders.
v
TABLE OF CONTENTS
LIST OF TABLES ................................................................................................................................. ix
LIST OF FIGURES ................................................................................................................................ ix

CHAPTER 1: INTRODUCTION .............................................................................................................. 1
1.1 Introduction ............................................................................................................................... 1
1.2 Objective and Scope ................................................................................................................. 2
1.3 Organization of Report .............................................................................................................. 4

CHAPTER 2: INTRODUCTION TO ACOUSTIC EMISSION TESTING ............................................... 5
2.1 Introduction to Nondestructive Testing ..................................................................................... 5
2.2 Introduction to Acoustic Emission Testing ................................................................................ 6
2.2.1 Selection of Testing Technique ...................................................................................... 6
2.2.2 Advantages and Limitations ........................................................................................... 6
2.2.3 Testing Specifications .................................................................................................... 7
2.2.4 Testing Standards .......................................................................................................... 7
2.2.5 Measurement Units for Acoustic Emission Testing ........................................................ 8
2.3 Fundamentals of Acoustic Emission Testing... ......................................................................... 8
2.3.1 Source Mechanisms ....................................................................................................... 8
2.3.2 Comparison with Other NDT Methods ........................................................................... 9
2.3.3 Applications of Acoustic Emission Testing ..................................................................... 9
2.3.4 Acoustic Emission Testing Equipment ......................................................................... 10
2.4 Data Interpretation... ............................................................................................................... 11
2.5 Waveform Parameters... ......................................................................................................... 14
2.6 General Acoustic Emission Monitoring Procedure... .............................................................. 16

CHAPTER 3: HISTORY OF ACOUSTIC EMISSION TESTING AND APPLICATIONS TO
STRUCTURAL CONCRETE ......................................................................................... 20
3.1 Early Observations .................................................................................................................. 20
3.1.1 Recording Acoustic Emission ....................................................................................... 20
3.1.2 Founders and Terminology .......................................................................................... 21
3.2 Acoustic Emission in Concrete Engineering ........................................................................... 22
3.3 Acoustic Emission in Reinforced Concrete ............................................................................. 22
3.4 Acoustic Emission in Prestressed Concrete ........................................................................... 30
3.5 Summary ................................................................................................................................. 34

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CHAPTER 4: ACOUSTIC EMISSION TESTING OF REPAIRED PRESTRESSED
CONCRETE BRIDGE GIRDERS .............................................................................. 36
4.1 Introduction ............................................................................................................................. 36
4.2 Research Significance ............................................................................................................ 37
4.3 Acoustic Emission Evaluation Criteria .................................................................................... 37
4.3.1 NDIS-2421 Criterion ..................................................................................................... 37
4.3.2 Signal Strength Moment Ratio Evaluation ................................................................... 38
4.4 Experimental Procedure ......................................................................................................... 38
4.4.1 Preliminary Investigation .............................................................................................. 38
4.4.2 Testing Equipment ....................................................................................................... 41
4.4.3 Instrumentation Setup .................................................................................................. 42
4.4.4 Conventional Measurements ........................................................................................ 47
4.4.5 Bridge Loading for Acoustic Emission Testing ............................................................. 47

CHAPTER 5: EXPERIMENTAL RESULTS AND DISCUSSION ........................................................ 58
5.1 Organization of Results and Discussion ................................................................................ 58
5.2 Pre-FRP Repair Results and Discussion ............................................................................... 58
5.2.1 Crack-Opening Displacement Analysis ........................................................................ 58
5.2.2 Pre-FRP Repair AE Evaluation Criteria Results .......................................................... 61
5.2.2.1 NDIS-2421 Criterion ........................................................................................ 61
5.2.2.2 Signal Strength Moment Ratio Evaluation ....................................................... 64
5.2.3 Crack Location using AE 2D-LOC Analysis Technique ............................................... 66
5.2.4 Summary and Conclusions .......................................................................................... 68
5.3 Differences in Pre- and Post-Repair Testing ......................................................................... 69
5.3.1 Bearing Pad Installation ............................................................................................... 69
5.3.2 Pre-Repair Bearing Pad Conditions ............................................................................. 70
5.3.3 Post-Repair Bearing Pad Conditions ........................................................................... 70
5.3.4 Post-Repair Procedural Changes ................................................................................ 70
5.3.5 Effects on Pre- and Post-Repair Comparison .............................................................. 74
5.4 Post-FRP Repair Results and Discussion ............................................................................. 75
5.4.1 Crack-Opening Displacement Analysis ........................................................................ 75
5.4.2 AE Evaluation Criteria Results ..................................................................................... 79
5.4.2.1 NDIS-2421 Criterion ........................................................................................ 79
5.4.2.2 Signal Strength Moment Ratio Analysis .......................................................... 88
5.4.3 Crack Location using AE 2D-LOC Analysis Technique ............................................... 93
5.4.4 Additional Evaluation Criteria ....................................................................................... 96
5.4.4.1 Channel Hit Frequency .................................................................................... 96
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5.4.4.2 Peak CSS Ratio ............................................................................................... 97
5.4.4.3 NDIS-2421 Criterion based on COD Ratio ...................................................... 99
5.5 Post-Repair Analysis Applied to Pre-Repair Data ............................................................... 102
5.6 Summary and Conclusions .................................................................................................. 105

CHAPTER 6: SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS .................................... 113
6.1 Summary .............................................................................................................................. 113
6.2 Conclusions from Field Testing ........................................................................................... 113
6.3 Recommendations for Future Study .................................................................................... 114

REFERENCES ................................................................................................................................... 116

APPENDIX A: CRACK-OPENING DISPLACEMENT ANALYSIS FIGURES .................................. 120

APPENDIX B: NDIS-2421 CRITERION ANALYSIS FIGURES ........................................................ 123

APPENDIX C: SSM RATIO ANALYSIS FIGURES .......................................................................... 146

APPENDIX D: AE 2D-LOC CRACK LOCATION FIGURES ............................................................ 153

APPENDIX E: ADDITIONAL EVALUATION CRITERIA FIGURES ................................................. 157

APPENDIX F: ON-SITE TESTING PICTURES ................................................................................. 160

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LIST OF TABLES

Table 4-1 PAC R6I-AST Sensor summary information (adapted from PCI 2002) ......................... 42
Table 4-2 AE test parameters ......................................................................................................... 43
Table 5-1 AE evaluation results (Xu 2008) ..................................................................................... 66
Table 5-2 Load truck weight distributions—pre-repair test (Bullock et al. 2011) ............................ 72
Table 5-3 Load truck weight distributions—post-repair test (Bullock et al. 2011) .......................... 73
Table 5-4 Comparison of trucks ST-6902 and ST-6538 (Bullock et al. 2011) ................................ 73
Table 5-5 Peak CSS ratios for post-repair test ............................................................................... 98
Table 5-6 Peak CSS ratios for pre-repair test .............................................................................. 104
Table 5-7 Adapted pre-repair test results ...................................................................... ...............107
Table 5-8 Post-repair test results .................................................................................................. 107

LIST OF FIGURES

Figure 1-1 Elevated spans of I-565 bridge in Huntsville, Alabama .................................................... 3
Figure 2-1 Basic four-channel acoustic emission test system (adapted from ASNT 2005) ............ 10
Figure 2-2 Illustration of Kaiser effect and Felicity effect (adapted from Pollock 1995) .................. 13
Figure 2-3 Features of a typical AE signal (adapted from Huang et al. 1998) ................................ 14
Figure 2-4 Calibration of AE sensor (Pollock 1995) ........................................................................ 18
Figure 3-1 Classification of damage recommended by NDIS-2421 (Ohtsu et al. 2002) ................. 24
Figure 3-2 Classification of AE data by load and calm ratio (Ohtsu et al. 2002) ............................. 25
Figure 3-3 Relaxation ratio results (Colombo et al. 2005) ............................................................... 26
Figure 3-4 Signal strength versus time (Ridge and Ziehl 2006) ...................................................... 27
Figure 3-5 CSS during initial load hold and reload hold (Ridge and Ziehl 2006) ............................ 28
Figure 3-6 Recorded AE events versus actual loading cycle history for an ordinary
reinforced beam (Shield 1997) ....................................................................................... 32
Figure 3-7 Recorded AE events versus actual loading cycle history for a prestressed
beam (Shield 1997) ........................................................................................................ 33
Figure 3-8 Sensor locations for load tests (Fowler et al. 1998) ....................................................... 34
Figure 4-1 Bridge cross section and transverse position of test trucks (Fason and
Barnes 2004) .................................................................................................................. 39
Figure 4-2 Girder cross section dimensions (Xu 2008) ................................................................... 39
Figure 4-3 I-565 layout and numbering system (Xu 2008) .............................................................. 40
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Figure 4-4 Cracks in east face of Span 11 Girder 7 ........................................................................ 41
Figure 4-5 Steel sheets on girder face ............................................................................................ 44
Figure 4-6 Sensor installation .......................................................................................................... 44
Figure 4-7 Sensor configuration on east face of Girder 8 (Xu 2008) ............................................... 45
Figure 4-8 Arrangement of Sensors 13–18 on Girder 8 .................................................................. 45
Figure 4-9 Sensor configuration on east face of Girder 7 (Xu 2008) ............................................... 46
Figure 4-10 Arrangement of Sensors 19–24 on Girder 7 .................................................................. 46
Figure 4-11 Standard load truck ST-6400 (pre-repair and post-repair) ............................................. 48
Figure 4-12 Standard load truck ST-6538 (post-repair)..................................................................... 49
Figure 4-13 Truck ST-6400 load configuration LC-6.5 for pre- and post-repair ................................ 50
Figure 4-14 Truck ST-6538 load configuration LC-6.5 for post-repair ............................................... 50
Figure 4-15 Footprint of ALDOT load trucks (ST-6400 and ST-6538) .............................................. 51
Figure 4-16 AE testing stop position locations .................................................................................. 53
Figure 4-17 Longitudinal test positions for Span 10 loading ............................................................. 54
Figure 4-18 Longitudinal test positions for Span 11 loading ............................................................. 55
Figure 4-19 Truck ST-6400 load configuration LC-6.0 for pre- and post-repair ................................ 56
Figure 4-20 Truck ST-6538 load configuration LC-6.0 for post-repair ............................................... 56
Figure 5-1 Crack-opening displacement during first night loading (Xu 2008) ................................. 60
Figure 5-2 COD and AE activity of Span 10 Girder 8 during second night (Xu 2008) .................... 61
Figure 5-3 Plot used in determining strain and calm ratios for Span 10 Girder 8 (Xu
2008) .............................................................................................................................. 63
Figure 5-4 Damage qualification based on NDIS-2421 method (Xu 2008) ..................................... 64
Figure 5-5 Signal strength moment (SSM) ratio during holds (Xu 2008) ........................................ 65
Figure 5-6 AE event location and crack pattern of Span 11 Girder 8 (Xu 2008) ............................. 67
Figure 5-7 AE event location and crack pattern of Span 11 Girder 7 (Xu 2008) ............................. 68
Figure 5-8 Post-repair cross section dimensions and strain gauge locations ................................. 71
Figure 5-9 Load truck ST-6902 (pre-repair unconventional truck) .................................................. 72
Figure 5-10 Crack-opening displacement during Night 1 loading of Span 10 ................................... 76
Figure 5-11 Crack-opening displacement during Night 1 loading of Span 11 ................................... 77
Figure 5-12 AE amplitude and COD versus time of Span 11 loading on Night 1 .............................. 78
Figure 5-13 K-factor based on original historic index equation ......................................................... 80
Figure 5-14 Historic index plot for SP10G7 on Night 2...................................................................... 81
Figure 5-15 Historic index and strain versus time for SP10G7 on Night 2 ........................................ 82
Figure 5-16 Derived K-factor for SP10G7 (N=90) ............................................................................. 83
Figure 5-17 Onset of AE for SP10G7 on Night 2 ............................................................................... 84
Figure 5-18 Maximum strain from Night 1 for SP10G7 ..................................................................... 85
Figure 5-19 CSS and strain versus time from SP10G7 loading on Night 1 ...................................... 86
x