The Use of Nondestructive Testing Methods for the Condition Assessment of Concrete Bridge Girders by Richard Cornelius Unruh, III B.A. Mathematics Colby College, 1997 B.S. Civil Engineering Northeastern University, 2003 SUBMITTED TO THE DEPARTMENT OF CIVIL AND ENVIRONMENTAL ENGINEERING IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ENGINEERING IN CIVIL AND ENVIRONMENTAL ENGINEERING AT THE MASSACHUSETTS INSTITUTE OF TECHNOLOGY JUNE 2004 0 2004 Richard C. Unruh, 1II. All rights reserved. The author hereby grants to MIT permission to reproduce and to distribute publicly paper and electronic copies of this thesis in whole or in part. Signature of Author: Dep fC in ironmental Engineering May 7, 2004 Certified by: Accepted by: Jerome J. Connor Profeor of Civil and Environmental Engineering fl Thesis Supervisor Heidi M. Nepf Associate Professor of Civil and Environmental Engineering Chairman, Committee for Graduate Students MASSACHUSETTS INS1TflTE OF TECHNOLOGY JUN 0 7 2004 LIBRARIES BARKER
72
Embed
The Use of Nondestructive Testing Methods for the ...
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
The Use of Nondestructive Testing Methods for theCondition Assessment of Concrete Bridge Girders
SUBMITTED TO THE DEPARTMENT OF CIVIL AND ENVIRONMENTALENGINEERING IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR
THE DEGREE OF
MASTER OF ENGINEERING IN CIVIL AND ENVIRONMENTALENGINEERING
AT THE
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
JUNE 2004
0 2004 Richard C. Unruh, 1II. All rights reserved.
The author hereby grants to MIT permission toreproduce and to distribute publicly paper and
electronic copies of this thesis in whole or in part.
Signature of Author:Dep fC in ironmental Engineering
May 7, 2004
Certified by:
Accepted by:
Jerome J. ConnorProfeor of Civil and Environmental Engineering
fl Thesis Supervisor
Heidi M. NepfAssociate Professor of Civil and Environmental Engineering
Chairman, Committee for Graduate Students
MASSACHUSETTS INS1TflTEOF TECHNOLOGY
JUN 0 7 2004
LIBRARIES
BARKER
The Use of Nondestructive Testing Methods for theCondition Assessment of Concrete Bridge Girders
by
Richard Cornelius Unruh, III
Submitted to the Department of Civil and Environmental Engineering onMay 7, 2004 in Partial Fulfillment of the Requirements for the Degree of
Master of Engineering in Civil and Environmental Engineering
ABSTRACTThere are over 594,000 publicly controlled bridges in the United States. Concreteand pre-stressed concrete bridges account for nearly 50% of the bridges in the USinventory. This proportion is increasing each year, as new bridges tend to beconstructed of concrete. This trend makes it vital for engineers to be able toaccurately assess the condition of concrete for maintenance and repair decisions.
The use of nondestructive testing methods can help reduce the backlog of deficientbridges in two ways. First, these techniques will allow inspectors to get a moreaccurate view of the condition of a bridge. The second way by which NDT can helpis by allowing inspectors to locate damage earlier.
This thesis is an attempt to capture the most current ideas for a very specificapplication of NDT: determining the condition of reinforced concrete bridges overalland bridge girders, in particular. To this end, attention is given to why NDT isneeded and what aspects of concrete condition can be addressed with NDT. SomeNDT methodologies that are, or may soon be, promising for concrete applicationsare discussed. Case studies are presented to demonstrate how NDT can be applied toconcrete bridge girders and proposals are made for future areas of study anddevelopment.
Thesis Supervisor: Jerome J. ConnorTitle: Professor of Civil and Environmental Engineering
Acknowledgements & Dedication
There are many people who have provided support and assistance during the writingof this thesis.
Professor Jerome Connor has been a source of advice on all matters, great and small.His insights have been invaluable and are greatly appreciated.
I need to thank my parents, Richard & Dawne Unruh, for their unwavering love andsupport in all of my endeavors. They have never questioned my path, only helped meto the next milestone.
I want to thank my parents-in-law, Jeff & Mary Smith. They have welcomed me intotheir family and hearts and provided love and support in all I do. I am fortunate tohave two families of which I am proud to be part.
Finally, and most importantly, I dedicate this thesis to my wife, Jenny. Without herlove and encouragement, I would not be where I am today. She has given me thestrength and courage to achieve goals that I never knew I had. This work is alsodedicated to my daughter, Rebecca. She has been an everlasting source of inspirationduring my many stressful moments over the past year and a half.
5
6
Table of ContentsA B STR A C T ..................................................................................................................... 3A cknow ledgem ents & D edication.................................................................................. 5List of Figures......................................................................................................................8List of Tables ....................................................................................................................... 91. Introduction................................................................................................................11
1.1. Scope and Purpose of Thesis ...................................................................... 121.2. State of Bridges in U S ............................................................................... 121.3. How N D T Can H elp .................................................................................. 16
2. Background on N D T.............................................................................................. 192.1. Issues & Barriers to U se of N D T................................................................ 19
3. Concerns for Reinforced Concrete Bridge G irders ............................................... 233.1. Rebar Corrosion......................................................................................... 243.2. Cracking..................................................................................................... 273.3. Chem ical Attack ........................................................................................ 273.4. H oneycom bing........................................................................................... 293.5. Creep, Shrinkage & V olum e Changes....................................................... 293.6. Strength of Concrete .................................................................................. 313.7. Condition of Post Tensioning Tendons .................................................... 313.8. Freeze-Thaw Dam age................................................................................ 31
4. Selected NDT Methods with Applications to Concrete Bridge Girders................334.1. Pulse V elocity........................................................................................... 344.2. Im pulse Response ...................................................................................... 354.3. Spectral Analysis of Surface W aves (SA SW )........................................... 364.4. M odal Testing........................................................................................... 374.5. A coustic Em issions M ethods.................................................................... 374.6. Im pact Echo ............................................................................................... 384.7. Fiber Optics ............................................................................................... 384.8. G alvanostatic Pulse Technique.................................................................. 39
5. Case Studies...............................................................................................................415.1. 1-40 Overpass: a W ork-in-Progress ........................................................... 415.2. NDT Corporation: Assessment of Concrete Arch Bridges........................495.3. Evaluation of Concrete Quality in a Bridge Deck and Detection of Voidsin Tendon D ucts in a Pre-stressed Slab ................................................................. 49
6. Future of N DT in Bridge M aintenance.................................................................. 556.1. H ealth M onitoring System s ...................................................................... 556.2. D ata Fusion................................................................................................ 586.3. Research N eeds......................................................................................... 606.4. Funding Needs ........................................................................................... 62
7. Conclusions................................................................................................................657.1. Benefits of NDT Use with Concrete Bridge Girders.................................657.2. K ey Barriers Still to Be A ddressed........................................................... 657.3. Research Recom m endations...................................................................... 66
List of FiguresFigure 1-1 :Bridge Proportions by Material Type [Chase & Washer, 1997].............. 11Figure 1-2: Bridge Age Distribution by Type [Chase & Washer, 1997]............... 14Figure 1-3: Material Proportions for Bridges, Total and Deficient [Chase & Washer,
19 9 7 ] .................................................................................................................. 15Figure 1-4: Deficiency Distribution by Age [Chase & Washer, 1997] .................. 15Figure 1-5: Location of Structural Deficiencies in Bridges [Chase & Washer, 1997]
.............................................16Figure 2-1: Concrete NDT Usage [Rolander, et al, 2001]..................................... 21Figure 2-2: Changes in NDT Usage over Time [Rolander, et al, 2001]................ 22Figure 5-1: Sketch of Overpass [adapted from Stubbs, et al, 1999 (2)] ................ 41Figure 5-2: Schematic of Approach Used to Identify Stiffness Properties of Baseline
and Existing Structures [Stubbs, et al (2), 1999].......................................... 43Figure 5-3: Damage Detection Model [Stubbs, et al, 1999 (2)] ............................ 43Figure 5-4: Surface Crack Pattern on the Deck [Stubbs, et al, 1999 (2)] .............. 46Figure 5-5: Comparison of Surface Crack Locations and Damage Localization
Results from the Field Measurements in December 1997 [Stubbs, et al, 1999(2 )]......................................................................................................................4 7
Figure 5-6; Comparison of Surface Crack Locations and Damage LocalizationResults from the Field Measurements in September 1998 [Stubbs, et al, 1999(2 )]......................................................................................................................4 7
Figure 5-7: Mobility x Mobility Slope Plot from the Impulse Response Test [YongH ao, et al, 2003]............................................................................................. 50
Figure 5-8: Core Sample Showing a Large Void [Yong Hao, et al, 2003] ........... 51Figure 5-9: Impact Echo Test Output for Same Location. Amplitude Spikes Indicate
Anomalous Areas [Yong Hao, et al, 2003].................................................... 51Figure 5-10: Fibrescope View of Void in Tendon Duct [Yong Hao, et al, 2003].....52Figure 5-11: Impact Echo Output Showing Void in Tendon Duct [Yong Hao, et al,
2 0 0 3] .................................................................................................................. 5 3Figure 6-1: Bridge Management System Flow Chart [Chase & Washer, 1997].......56Figure 6-2: Risk-Informed Expenditure Allocation Flowchart [Ayyub, et al, 2003] 57Figure 6-3: Factors to Consider in the Development of a Data Fusion System [Gros,
19 9 7 ] .................................................................................................................. 5 8Figure 6-4: Schematic for Development of a NDT Fusion Engine [Gros, 1997]...... 59Figure 6-5: Design of an Expert System to Assist in NDT Investigations [Gros,
19 9 7 ] .................................................................................................................. 6 0Figure 6-6: Research Needs for NDT [Rolander, et al, 2001]............................... 61Figure 6-7: Percentage of Inspections Teams with a PE [Rolander, et al, 2001]......63
8
List of TablesTable 3-1: Concrete Deterioration Diagnostics [Heckroodt, 2002].............................24Table 3-2: The Manifestation of Reinforcement Corrosion [Heckroodt, 2002]............25Table 3-3: Condition Surveys to Evaluate Reinforcement Corrosion [Heckroodt,
2 0 0 2 ] .......................................................................................................................... 2 6Table 5-1: Member Properties [Stubbs, et al, 1999 (2)]...............................................42Table 5-2: Identified Material Properties of the Baseline Structure (December 1997)
[Stubbs, et al, 1999 (2)] ........................................................................................ 43Table 5-3: Predicted Damage Magnitudes (December 1997) [Stubbs, et al, 1999 (2)] ...44Table 5-4: Bending Stiffnesses of the Structure (December 1997) [Stubbs, et al,
19 9 9 (2 )] .................................................................................................................... 4 4Table 5-5: Identified Material Properties of the Baseline Structure (September 1998)
[Stubbs, et al, 1999 (2)] ........................................................................................ 45Table 5-6: Predicted Damage Magnitudes (September 1998) [Stubbs, et al, 1999 (2)] ... 45Table 5-7: Bending Stiffnesses of the Structure (September 1998) [Stubbs, et al,
19 9 9 (2 )] .................................................................................................................... 4 6Table 6-1: Proposed Allocation for Additional Funding [Rolander, et al, 2001]..........62Table 6-2: Bridge Inspection Policy & Procedural Change Suggestions [Rolander, et
Electronic data from Inspections w/direct mput into BMS 6Require element-level inspection data 1Post bridge repair list on Internet 1 -
Devote more time to inspection and inventory management - 2
Training/Continuing Education Related
Continuing education requirements for team leaders 2 -
Momtor and audit content of NHI course 1Require Bridge Insp. Training Course for other team members 1Hold single-day refresher course more frequently - 1Standardize continuing education requirements - 1
Inspection Operation/Procedure ImprovementsBetter access for inspection in urban areas 2 -
Additional field time by bridge maintenance engineers 1 -Improved procedures for inspection of prestressed concrete 1 -Fully documented procedures in a Bridge Inspection Policy 1
ManualRegulations for scour (not guidelines) 14- to 5-year cycle for Fracture-Critical Members and Special 1
Inspection of major bridgesStatewide Quality Control 1Summertime inspections 1Mandatory inspections for timber bridges more than 30 years
oldStructure Inventory and Appraisal (SI&A) form changes too
quickly, keep same form for a minimum of 3 to 4 yearsMore equipment to check scour conditions 1
MiscellaneousPay consultants on a unit basis, not hourly basis 1More Federal money (contract inspections, more personnel, - 5
training, and software)
64
7. Conclusions
Concrete continues to be the material of choice for bridge construction. Since the
1970s, new concrete bridges have outnumbered new steel bridges by a significant
margin. With the increase in concrete bridges comes a growing need for tools and
technology to evaluate the structures for maintenance decisions. While steel behavior
is well understood and NDT methods for steel are fairly well established, concrete
lags in both areas. There are many potential benefits to the use of NDT with concrete
bridge girders. These benefits will be realized with further research.
7.1. Benefits of NDT Use with Concrete Bridge Girders
NDT technology can improve the inspection of concrete bridge girders in several
ways. The data obtained from NDT methods is unbiased and, with the use of
multiple sensors, relatively complete. NDT technologies are available that can
provide information about the size, location and orientation of voids, the condition of
reinforcing steel and post-tensioning tendons, and the condition of grout in tendon
ducts. Some methods can also predict elastic properties of the concrete such as
Young's moduli and Poisson's ratio. The Pulse Velocity method has shown promise
for predicting compressive strength, as well. When evaluated by an experienced,
knowledgeable inspector, this data will allow for a more complete understanding of
the behavior and condition of the bridge members than is possible with more
traditional inspection methods. With the more portable methods, or embedded
sensors, NDT can make the inspection process easier, faster and safer. The use of
embedded sensors will provide real-time data that can be incorporated into a bridge
management system to streamline maintenance and repair decisions. All of these
advantages will lead to the additional benefit of reduced expenses.
7.2. Key Barriers Still to Be Addressed
Before the full benefits of NDT can be realized, there are several barriers to be
overcome. Engineers need a more complete understanding of the behavior of
65
concrete under service loads. The response of concrete to the various NDT methods
needs to be better understood, as well, to allow inspectors to properly interpret the
readings obtained from the tests. Capabilities and limitations of the techniques must
also be established; documenting what can and cannot be learned from their use.
Data is needed on the long-term behavior of bridges, particularly relating to the
effects of damage on this behavior. This information can then be used to predict
remaining bridge life and possible failure modes. Finally, additional funding is
needed to properly staff, equip, and train inspection teams. Financial constraints are
consistently cited as an important factor in decisions to implement or expand the use
of NDT methods in bridge inspections. This funding is especially urgent for the
public transportation agencies that oversee the majority of the bridges in the U.S.
Private corporations tend to claim broader use of NDT, as well as more stringent
training requirements. Additional funding will allow public agencies to adopt
guidelines and policies to ensure accurate and reliable inspections.
7.3. Research Recommendations
In order for NDT to become a reliable, functional tool for bridge girder assessment,
several areas of research need to be addressed. This research will support the needs
addressed in section 7.2. Based on these needs, research recommendations can be
broken down into four categories:
- Material behavior under service loads & extreme events* Material response to NDT tests" Development of field-ready testing equipment- Data collection of bridge failure modes for risk assessment
The order in which this research is undertaken is controlled in part by prerequisite
needs for knowledge. The material behavior and response to NDT must be
understood before equipment needs can be assessed and data collection performed.
Predictions can be made based on current knowledge, but continuing research must
be focused to address the validity of any assumptions being made. Solving
66
equipment needs will require cooperation among civil, electrical and computer
engineers, as well as materials scientists and many other contributors. Data collection
must be an ongoing process. As more data is added to knowledge banks, predictions
of failure risks will become more accurate and assumptions will be verified or
corrected.
67
References
Aidoo, John, Kent Harries & Michael Petrou, "Fatigue Behavior of CFRP-Strengthened Reinforced Concrete Bridge Girders", AZ-ICCI Conference Paper,June 2002.
American Society of Civil Engineers, "2001 Report Card for America'sInfrastructure", ASCE, Reston, VA, 2001, access at http://www.asce.org/reporteard
American Society of Civil Engineers, "2003 Progress Report, an Update to the 2001Report Card for America's Infrastructure", ASCE, Reston, VA, 2003, access athttp://www.asce.org/reportcard
Ansari, Farhad, ed., Condition Monitoring of Materials and Structures, ASCE, NewYork, NY, 2000.
Ansari, Farhad, "Ral-Time Monitoring of Concrete Structures by Embedded OpticalFibers", in Nondestructive Testing of Concrete Elements and Structures, FarhadAnsari & Stein Sture, eds., ASCE, New York, NY, 1992.
Atkan, A. E., C. J. Tsikos, F. N. Catbas, K. Grimmelsman & R. Barrish, "Challengesand Opportunities in Bridge Health Monitoring", in Structural Health Monitoring,2000, Chang, Fu-Kuo, ed., Technomic Publishing Co., Inc., Lancaster, PA, 1999.
Ayyub, Bilal M. & Clara Popescu, "Risk-Based Expenditure Allocation forInfrastructure Improvement", Journal of Bridge Engineering, November/December2003, ASCE, Washington, DC, 2003.
Azizinamini, Atorod, Aaron Yakel & Magdy Abdelrahman, eds., High PerformanceMaterials in Bridges, ASCE, New York, NY, 2003.
Better Roads Magazine, "2003 Bridge Inventory", Better Roads Magazine, DesPlaines, IL, November 2003. Available:http://www.betterroads.com/articles/bridgeinv.htm
Bolton, R., N. Stubbs, S. Park, S. Choi, & C. Sikorsky, "Measuring Bridge ModalParameters for Use in Nondestructive Damage Detection and PerformanceAlgorithms", Proc. of the 17th International Modal Analysis Conf. Orlando, FL,1999.
Chajes, Michael J., Harry W. Stanton, III & Dennis O'Shea, "Bridge-ConditionAssessment and Load Rating Using Nondestructive Evaluation Methods", paper no.5B0058 in Transportation Research Record 1696, Transportation Research Board,National Research Council, Washington, DC, 2000.
68
Chang, Peter C. and S. Chi Liu, "Recent Advances in Nondestructive Evaluation ofCivil Infrastructures", Journal of Materials in Civil Engineering, May/June 2003,ASCE, Reston, VA, 2003.
Chase, Stephen B. & Glenn Washer, "Nondestructive Evaluation for BridgeManagement in the Next Century", Public Roads, July 1997, U.S. Department ofTransportation, Federal Highway Administration, Washington, DC. Available:http://www.tfhrc.gov/pubrds/july97/ndeiuly.htm
Davis, Allen G. & Claus Germann Petersen, "Nondestructive Evaluation ofPrestressed Concrete Bridges Using Impulse Response", presented at theInternational Symposium on Non-Destructive Testing in Civil Engineering 2003,Berlin, Germany, September 2003.
Duke, John C., Jr., "Final Contract Report: Health Monitoring of Post TensionTendons", report of contract research sponsored by Virginia Transportation ResearchCouncil, project no. 02-0178-07, VTRC, Charlottesville, VA, October 2002.
Fdcdoaru, I., "Evaluation of Damage in Concrete Units Due to Earthquake Action,and Repair by Ultrasonic Technique", in Emerging Technologies in NDT, DannyVan Hemelrijck, Athanassios Anastassopoulos & Theodore Philippidis, eds., A.A.Balkema, Rotterdam, Netherlands, 2000.
Feldman, R.F., "CBD- 119 Volume Change and Creep of Concrete", CanadianBuilding Digest, National Research Council Canada, November 1969,available: http://irc.nrc-cnrc.gc.ca/cbd/cbd 119e.html
Gros, X.E., NDT Data Fusion, John Wiley & Sons, Inc., New York, NY, 1997.
Heckroodt, Renier Oelof, Guide to Deterioration and Failure of Building Materials,Thomas Telford Books, London, UK, 2002.
Huston, D., P. Fuhr, P. Kajenski & D. Snyder, "Concrete Beam Testing with OpticalFiber Sensors", in Nondestructive Testing of Concrete Elements and Structures,Farhad Ansari & Stein Sture, eds., ASCE, New York, NY, 1992.
Jackson, Donald R. "Time for a Physical: TE-42 Assessment of Physical Conditionof Reinforced Concrete Structures", HighwayTECHNET, 1999.available: http://www.library.unt.edu/gpo/OTA/tech/struct/te42.htm
Kalinski, Michael E., "Nondestructive Characterization of Damaged and RepairedAreas of a Concrete Beam Using the SASW Method", in Innovations inNondestructive Testing of Concrete, Stephen Pessiki & Larry Olson, eds., ACI,Farmington Hills, MI, 1997.
69
Klinghoffer, Oskar, Thomas Frolund, & Ervin Poulsen, "Rebar Corrosion RateMeasurements for Service Life Estimates", ACI Fall Convention presentation,Toronto, Canada, 2000.
Kroggel, 0., "Ultrasound Application in Civil Engineering - Future Steps", inEmerging Technologies in NDT, Danny Van Hemelrijck, AthanassiosAnastassopoulos & Theodore Philippidis, eds., A.A. Balkema, Rotterdam,Netherlands, 2000.
Landis, Eric, Michael Peterson, Scott Selleck, Surendra Shah, Zongjin Li, AlanZdunek and David Prine, "Developments in NDE of Concrete", NorthwesternUniversity Center for Advanced Cement-Based Materials and BIRL IndustrialResearch Laboratory, June 1994. Accessed online April 7, 2004 athttp://iti.acns.nwu.edu/pubs/landis.html
Lenett, Michael S., Ann Greisman, Arthur J. Helmicki & A. Emin Aktan,"Subjective and Objective Evaluations of Bridge Damage", paper no. 99-0411 inTransportation Research Record 1688, Transportation Research Board, NationalResearch Council, Washington, DC, 1999.
Letoureux, R., "Bacteriogenic Corrosion of Concrete", conference paper, BiarritzColloque 2001, Biarritz, France, October, 2001.
Moerman, W., L. Taerwe, W. De Waele, J. Degrieck & R. Baets, "RemoteMonitoring of Concrete Elements by Means of Bragg Gratings"., ", in StructuralHealth Monitoring, 2000, Chang, Fu-Kuo, ed., Technomic Publishing Co., Inc.,Lancaster, PA, 1999.
Ndambi, J. M., W.P. De Wilde, J. De Visscher, J. Vantomme, B. Peewters, M.A.Wahab, & G. De Roeck, "Modal Testing as a Tool for Non-Destructive Testing ofConcrete Structures", in Emerging Technologies in NDT, Danny Van Hemelrijck,Athanassios Anastassopoulos & Theodore Philippidis, eds., A.A. Balkema,Rotterdam, Netherlands, 2000.
Nemati, Kamran M., "CM5 10- Advanced Construction Techniques: VolumeChanges and Creep of Concrete", course material, University of Washington, Seattle,WA, 2003
Olson, Larry D., "Sonic NDE of Structural Concrete", in Nondestructive Testing ofConcrete Elements and Structures, Farhad Ansari & Stein Sture, eds., ASCE, NewYork, NY, 1992.
Ouyang, C., E. Landis & S. P. Shah, "Damage Assessment in Concrete UsingAcoustic Emission", in Nondestructive Testing of Concrete Elements and Structures,Farhad Ansari & Stein Sture, eds., ASCE, New York, NY, 1992.
Popovics, John. S. & Maja Bystrom, "Effective Use of Surface Waves for NDE ofConcrete", in Proceedings of the 14th ASCE Engineering Mechanics Conference,Austin, Texas, May 21-24, 2000, ASCE, Reston, VA, 2000.
Popovics, Sandor, "Analysis of the Concrete Strength versus Ultrasonic PulseVelocity Relationship" Back to Basics, American Society for NondestructiveTesting, February 2001. Accessed online April 7, 2004 at:http://www.asnt.org/publications/materialscvaI/basics/feb0 I basics/febO I basics.htm
Prine, David W., "Problems Associated with Nondestructive Evaluation of Bridges",in Proceedings of SPIE - The International Society for Optical Engineering, v 2456,June 1995, Proceedings from the Nondestructive Evaluation of Aging Bridges andHighways Conference, Oakland, CA, 1995.
Rolander, D. D., B.M. Phares, B.A. Graybeal, M.E. Moore, and G.A. Washer,"Highway Bridge Inspection: State-of-the-Practice Survey," paper no. 01-2867 inTransportation Research Record, no. 1749, pp 73 - 81, 2001.
SCI, "Sulphate Attack in Concrete", Sulphur, No. 270, September-October 2000,Society of Chemical Industry, Chatham, NJ, 2000.
Stubbs, N., C. Sikorsky, S. Park, S. Choi & R. Bolton, "A Methodology toNondestructively Evaluate the Structural Properties of Bridges" Proc. of the 17th
International Modal Analysis Conf. Orlando, FL, 1999 (1).
Stubbs, N., C. Sikorsky, S. Park, S. Choi & R. Bolton, "Verification of aMethodology to Nondestructively Evaluate the Structural Properties of Bridges" inStructural Health Monitoring, 2000, Chang, Fu-Kuo, ed., Technomic Publishing Co.,Inc., Lancaster, PA, 1999 (2).
Tanaka, Yohiki, Hirotaka Kawano, Hiroshi Watanabe & Tomoyoshi Nakajo, "Studyon Required Cover Depth of Concrete Highway Bridges in Coastal Environment",presented at the 17th U.S.-Japan Bridge Engineering Workshop 2001, Tsukuba,Japan, November 2001.
71
Uomoto, Taketo, ed., Non-Destructive Testing in Civil Engineering, 2000, Elsevier,New York, NY, 2000.
De Visscher, J., W.P. De Wilde, J.M. Ndambi, J. Vantomme, B. Peeters, & G DeRoeck, "Damage Evaluation in Reinforced Concrete Using DampingMeasurements", in Emerging Technologies in NDT, Danny Van Hemelrijck,Athanassios Anastassopoulos & Theodore Philippidis, eds., A.A. Balkema,Rotterdam, Netherlands, 2000.
Washer, Glenn A., "Developing NDT Technologies for Highway Bridges", inMaterials Evaluation, November 1999, American Society for NondestructiveTesting, Columbus, OH, 1999.
Yong Hao, Zheng, Ng Kee Ee & Ong John Wei, "Evaluation of Concrete Structuresby Advanced Nondestructive Test Methods - Impact Echo Test, Impulse ResponseTest and Radar Survey", presented at the International Symposium on Non-Destructive Testing in Civil Engineering 2003, Berlin, Germany, September 2003.