ABSTRACT
Non-destructive ultrasonic inspection is an effective technique to ensure structural integrity of steel bridges. Quantitative information on flaw size, location and orientation is required for cost-effective maintenance of bridge components by implementation of the “retirement-for-cause” concept. This is especially true for such fracture-critical bridge structures as pinned connections, fasteners and welded joints.
One of the major problems in presenting NDT data is how to visualize the results of an inspection. Using comprehensive ultrasonic images of the inspected areas bridge managers and engineers can make rational decisions on steps needed to correct the problem.
A two-step technique for ultrasonic inspection of pins in pin-hanger connections is discussed in this paper. First the ultrasonic technique is applied in conjunction with a portable ultrasonic flaw detector. This test serves to detect an irregularity of any kind in the inspection zone. The time required for the test will be small and the equipment used should be portable and inexpensive. If the pin condition requires a more detailed inspection, a sophisticated data acquisition and imaging system will be used. This system can provide information on flaw configuration, and distinguish cracks from wear groves in the load bearing locations.
The ultrasonic inspection technique is used in conjunction with a portable imaging device for real-time data acquisition, signal and image processing, and documentation of the inspection results. Ultrasonic images have been obtained for fatigue cracks implanted into pins. The sizes, geometries, and locations of the implanted cracks in the sample are based on statistical data from previous NDI of similar pins. All implanted flaws are fully documented with drawing and verification of location by both mechanical and ultrasonic measurements to provide a base for calibration and subsequent training of operators.
