FHWA-HRT-04-042
View PDF Version (1.29 MB)
Turner-Fairbank
Highway Research Center
6300 Georgetown Pike
McLean,
VA 22101
In June 1983, a failed hanger pin initiated the tragic collapse of one span of the Mianus River Bridge on the Connecticut Turnpike near Greenwich, CT. This incident resulted in the deaths of three motorists. Following the collapse, there was an immediate increase in interest in the inspection and condition evaluation of bridge hanger pins. Ultrasonic inspection is one of the most reliable methods used to inspect hanger pins, and it has become the primary method of performing a detailed inspection of an in-service hanger pin.
This report provides background information regarding hanger pins in general and discusses the field ultrasonic techniques, including methods, results, and limitations of each method. The report provides a comprehensive document describing the fundamentals of ultrasonic hanger pin inspection and can be used by State transportation agencies that are either inspecting pins themselves or contracting for inspection services. In addition, a limited experimental program was utilized to emphasize, and more completely explain, some important aspects of ultrasonic pin inspection. This report will be of interest to bridge engineers, designers, and inspectors who are involved with the inspection of hanger pin assemblies used in our Nation’s highway bridges.
T. Paul Teng,
P.E.
Director,
Office of Infrastructure
Research and Development
NOTICE
This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for its contents or use thereof. This report does not constitute a standard, specification, or regulation.
The U.S. Government does not endorse products or manufacturers. Trade and manufacturers’ names appear in this report only because they are considered essential to the object of the document.
1. Report No. |
2. Government Accession No. |
3. Recipient’s Catalog No. |
||||
4. Title and Subtitle| |
5. Report Date |
|||||
6. Performing Organization Code |
||||||
8. Performing Organization Report No. |
||||||
7. Author(s) |
||||||
9. Performing Organization Name and Address |
10. Work Unit No. (TRAIS) |
|||||
11. Contract or Grant No. |
||||||
13. Type of Report and Period Covered |
||||||
12. Sponsoring Agency Name and Address |
||||||
14. Sponsoring Agency Code |
||||||
15. Supplementary Notes |
||||||
16. Abstract A failed hanger pin initiated the tragic collapse of one span of the Mianus River Bridge in Greenwich, CT on June 28, 1983, resulting in the deaths of three motorists. Following the collapse, there was an immediate increase of interest in the inspection and condition evaluation of bridge hanger pins. Ultrasonic inspection has become the primary method of performing detailed inspection of in-service hanger pins. The document describes the fundamentals of ultrasonic testing and general inspection requirements that can be used by State transportation agencies or by others performing ultrasonic hanger pin inspection. In addition, five hanger pins, with known defects, were inspected to emphasize and more completely explain some important aspects of ultrasonic hanger pin inspection. Items included in the fundamental review are the pulse-echo technique, pitch-catch technique, decibel scale, piezoelectric effect, beam diffraction, beam absorption, beam spread (beam divergence), beam centerline location, and distance amplitude correction. Items included in the general inspection requirement section are cleaning and coupling requirements, interpretation of signals, defect sizing techniques, effect of wear grooves, phenomena of acoustic coupling, inspection documentation, data collection, and inspector qualifications and certifications. Results from the experimental program include beam diffraction graphs, distance amplitude correction curves, sensitivity analysis of straight and angled beams, defect sizing analysis, and verification of the acoustic coupling phenomena. |
||||||
17. Key Words |
18. Distribution Statement |
|||||
19. Security Classif. (of this report) |
20. Security Classif. (of this page) |
21. No. of Pages |
22. Price |
Form DOT F 1700.7 (8-72) Reproduction of completed page authorized
1. INTRODUCTION
1.1. BACKGROUND
1.2. OBJECTIVE
2.1. ULTRASONIC TESTING EQUIPMENT
2.1.1. Fundamentals of Ultrasonic Waves
2.1.1.1. Pulse-Echo Technique
2.1.1.2. Pitch-Catch Technique
2.1.2. Decibel Scale
2.1.3. Transducers
2.1.4. Ultrasonic Beam Characteristics and Important Formulae
2.1.4.1. Beam Attenuation
2.1.4.1.1. Beam diffraction
2.1.4.1.2. Beam absorption
2.1.4.2. Beam Spread (Beam Divergence)
2.1.4.3. Beam Centerline Location
2.1.5. Distance Amplitude Correction
2.2. GENERAL HANGER PIN INSPECTION REQUIREMENTS
2.2.1. Cleaning and Coupling Requirements
2.2.2. Scanning Patterns
2.2.3. Application and Sensitivity of Straight and Angle Beam Transducers
2.2.4. Interpretation of Ultrasonic Testing Signals
2.2.5. Defect Sizing Techniques
2.2.5.1. Probe Movement Techniques
2.2.5.1.1. The 6-dB drop technique
2.2.5.1.2. The 20-dB drop technique
2.2.5.1.3. The time-of-flight diffraction technique
2.2.5.2. Amplitude Techniques
2.2.5.2.1. The comparator block technique
2.2.5.2.2. The distance amplitude correction technique
2.2.5.2.3. The distance grain size technique
2.2.6. Wear Grooves
2.2.7. Acoustic Coupling
2.3.1. Physical Measurements
2.3.2. Visual Assessments
2.3.3. Ultrasonic Testing Data Collection
2.4. INSPECTOR QUALIFICATIONS AND CERTIFICATIONS
3.1. INTRODUCTION
3.2. INSPECTION SPECIMENS
3.2.1. Side-Drilled Hole Test Block
3.2.2. Manufactured Cracked Pins
3.2.3. Pin/Hanger Mockup
3.3. TESTING PROGRAM
3.3.1. Beam Diffraction
3.3.2. Distance Amplitude Correction
3.3.3. Angle and Straight Beam Sensitivity to Cracks
3.3.4. Defect Sizing
3.3.5. Acoustic Coupling
4.1. BEAM DIFFRACTION
4.2. DISTANCE AMPLITUDE CORRECTION
4.3. ANGLE AND STRAIGHT BEAM SENSITIVITY TO CRACKS
4.4. DEFECT SIZING
4.5. ACOUSTIC COUPLING
Figure 1. Model of an elastic material
Figure 2. Longitudinal wave
Figure 3. Shear wave
Figure 4. Basic principle of pulse-echo technique
Figure 5. Sketch of a typical ultrasonic A-scan
Figure 6. Influence of distance on reflected ultrasonic signal
Figure 7. Influence of shadow effects on ultrasonic signal
Figure 8. Influence of defect orientation on ultrasonic signal
Figure 9. Influence of defect size on ultrasonic signal
Figure 10. Schematic of direct pitch-catch technique
Figure 11. Schematic of indirect pitch-catch technique
Figure 12. Piezoelectric effect
Figure 13. Schematic of a straight beam piezoelectric ultrasonic probe
Figure 14. Schematic of an angle beam piezoelectric ultrasonic probe
Figure 15. Concept for generating distance amplitude correction curves
Figure 16. Typical pin/hanger assembly
Figure 17. Application of a straight beam transducer
Figure 18. Application of an angle beam transducer
Figure 19. Typical physical measurements
Figure 20. Sample ultrasonic test data
Figure 21. SDHTB details
Figure 22. Photograph of the SDHTB
Figure 23. Typical pin geometry
Figure 24. Pin 1 defect details
Figure 25. Pin 2 defect details
Figure 26. Pin 3 defect details
Figure 27. Pin 4 defect details
Figure 28. Pin 5 defect details
Figure 29. Pin/hanger mockup details
Figure 30. Beam diffraction results for 8-degree, 5-MHz, 12.7-mm diameter transducer
Figure 31. Beam diffraction results for 0-degree, 5-MHz, 12.7-mm diameter transducer
Figure 32. Beam diffraction results for 0-degree, 2.25-MHz, 25.4-mm diameter transducer
Figure 33. Beam diffraction results for 11-degree, 2.25-MHz, 12.7-mm diameter transducer
Figure 34. Beam diffraction results for 14-degree, 2.25-MHz, 12.7-mm diameter transducer
Figure 35. Beam diffraction results for 8-degree, 2.25-MHz, 19-mm square transducer
Figure 36. Distance amplitude correction curve for 8-degree, 5-MHz, 12.7-mm diameter transducer
Figure 37. Distance amplitude correction curve for 0-degree, 5-MHz, 12.7-mm diameter transducer
Figure 38. Distance amplitude correction curve for 0-degree, 2.25-MHz, 25.4-mm diameter transducer
Figure 39. Distance amplitude correction curve for 11-degree, 2.25-MHz, 12.7-mm diameter transducer
Figure 40. Distance amplitude correction curve for 14-degree, 2.25-MHz, 12.7-mm diameter transducer
Figure 41. Distance amplitude correction curve for 8-degree, 2.25-MHz, 19-mm square transducer
Figure 42. Pin 1 testing results
Figure 43. Pin 2 testing results
Figure 44. Pin 3 testing results
Figure 45 Pin 4 testing results
Figure 46. Pin 5 testing results
Figure 47. Photograph of pulse-echo setup using 14-degree transducer
Figure 48. UT scan utilizing pulse-echo technique with a 14-degree transducer
Figure 49. Photograph of pitch-catch setup using 0-degree transducers
Figure 50. UT scan utilizing pitch-catch technique using 0-degree transducers
Figure 51. Photograph of pitch-catch setup using 0-degree receiving and 14-degree transmitting transducers
Figure 52. UT scan utilizing pitch-catch technique using 0-degree and 14-degree transducers
LIST OF TABLES
Table 1. Defect size data
Table 2. Defect sizing error
1. INTRODUCTION
1.1. BACKGROUND
A failed hanger pin initiated the tragic collapse of one span of the Mianus River Bridge in Greenwich, CT, on June 28, 1983, resulting in the deaths of three motorists. The collapse sparked an immediate increase of interest in the inspection and condition evaluation of bridge hanger pins. Ultrasonic inspection has become the primary method of performing detailed inspection of in-service hanger pins.
1.2. OBJECTIVE
The research objective is to develop a document describing the fundamentals of ultrasonic hanger pin inspection that can be used by State transportation agencies that are either inspecting pins themselves or contracting for inspection services. In addition, a limited experimental program is utilized to emphasize, and more completely explain, some important aspects of ultrasonic pin inspection.
FHWA-HRT-04-042 |
TFHRC Home | FHWA Home | Feedback United States Department of Transportation - Federal Highway Administration |