FATIGUE TEST OF A THREE-SPAN COMPOSITE HIGHWAY BRIDGE

Abstract

A three-span continuous composite bridge of modern design was field tested under fatigue loading which produced stresses equal to or greater than design stresses. Both the primary fatigue loading and loading for dynamic-property tests were imposed by a moving mass closed-loop electrohydraulic-actuator system. During the fatigue loading the bridge was inspected periodically by eight different inspection mthods. Inspection methods included visual, ultrasonic, radiographic, acoustic emission and dynamic-signature techniques. A total of 18 fatigue cracks developed at the ends of welded cover plates and two fatigue cracks developed in base metal which was not adjacent to welds. The fatigue life in regions where the stress range was 22.5 ksi was considerably longer than would be predicted, however, the fatigue life in other regions where the stress range was only 8.7 ksi was considerably shorter than would be predicted on the basis of current code requirements. /FHWA/