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Proceedings Paper

NDT applications in a successful fracture critical bridge inspection program and anchor bolt inspection program
Author(s): Philip E. Fish
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Paper Abstract

In 1978, Wisconsin Department of Transportation discovered major cracking on a two-girder, fracture critical structure, just four years after it was constructed. In 1981, on the same structure, now seven years old, major cracking was discovered in the tie girder flange of the tied arch span. This is one example of the type of failures that transportation departments discovered on welded structures in the 1970's and '80's. The failures from welded details and pinned connections lead to much stricter standards for present day designs. All areas were affected: design with identification of fatigue-prone details and classification of fatigue categories; material requirements with emphasis on toughness and weldability; increased welding and fabrication standards with licensure of fabrication shops to minimum quality standards including personnel; and an increased effort on inspection of existing bridges, where critical details were overlooked or missed in the past. FHWA inspection requirements for existing structures increased through this same time period, in reaction to the failures that had occurred. Obviously, many structures in Wisconsin were not built to the standards now required, thus the importance for quality inspection techniques. The new FHWA inspection requirements now being implemented throughout the nation require an in-depth, hands-on type inspection at a specified frequency, on all fracture critical structures. Wisconsin Department of Transportation started an in-depth inspection program in 1985 and made it a full time program in 1987. This program included extensive nondestructive testing. Ultrasonic inspection has played a major role in this type of inspection. All fracture critical structures, pin and hanger systems, and pinned connections are inspected on a five-year cycle now. The program requires an experienced inspection team and a practical inspection approach. Extensive preparation is required with review of all design, construction, and maintenance documents. An inspection plan is developed from the review and downloaded to a laptop computer. Inspection emphasis are on 'hands on' visual and nondestructive evaluation. Report documentation includes all design plans, pictorial documentation of structural deficiencies, nondestructive evaluation reports, conclusions, and recommendations. Planned changes in the program include implementation of an engineering work station as a 'single source' information file and reporting file for the inspection program. This would include scanning all current information into the file such as design, construction, and maintenance history. It would also include all inspection data with pictures. Inspections would be performed by downloading data onto a laptop and then uploading after completion of inspection. Pictures and nondestructive data would be entered by digital disks.

Paper Details

Date Published: 19 May 1995
PDF: 17 pages
Proc. SPIE 2456, Nondestructive Evaluation of Aging Bridges and Highways, (19 May 1995); doi: 10.1117/12.209760
Show Author Affiliations
Philip E. Fish, Wisconsin Dept. of Transportation (United States)

Published in SPIE Proceedings Vol. 2456:
Nondestructive Evaluation of Aging Bridges and Highways
Steven B. Chase, Editor(s)

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