The purpose of this project is to test and evaluate the Acoustic Emission Bridge Monitor through demonstrations and field trials, and to develop Application Guidelines and produce two educational videotapes.

Locating and evaluating cracks in steel bridges is a difficult and time consuming process. With about 90,000 steel bridges on the Federal-aid highway system, bridge inspection personnel spend many hours looking for cracks and bridge engineers spend many more hours evaluating the severity of the cracks found. Most cracks cannot be located visually until they are at least ½inch long and a significant portion of the fatigue life of the detail has been lost. Cracks can be found much earlier and important evaluations can be made of known cracks by using acoustic emission (AE) testing equipment.

There have been three types of AE field trials:

1. Monitoring bridge details with fatigue cracks caused by out-of-plane bending and similar uncracked details.

2. Checking details on bridge structures that had been inspected with ultrasonic equipment and that yielded unclear results.

3. Testing areas that had been retrofitted to strengthen a cracked detail.

The AE monitoring of cracked and uncracked (similar) details on one structure showed no cracks to be propagating at the details where there were no visible cracks. However, on another structure, the AE monitoring located a small crack beneath the paint where it could not be visually located. Ultrasonic inspection on two structures yielded unclear results and AE monitoring showed no active cracks. On a third structure, where ultrasonic inspection revealed an internal anomaly in a weld but was unable to characterize the stability (actively growing or passive) of the anomaly, AE monitoring revealed that the anomaly was indeed active. The weld has been cored, but the final report on the exactnature of the anomaly has not been published.

The project has concluded and the two videotapes and final report are available from the Office of Technology Applications.

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HIGHWAYTECHNET   VIRTUAL EXPO   STRUCTURES INDEX

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U.S. Department of Transportation
Federal Highway Administration