Use of fatigue fuses for prediction of fatigue life of steel bridges

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The fatigue fuse is a device for predicting the fatigue life of steel highway bridge members when the bridge is subject to variable loads. The fuse is calibrated so that the cracking of each of its four legs can be related to damage in the structure. In a preliminary laboratory study, fatigue fuses are attached to eight steel girders, selected to represent three types of structural details found in existing highway bridges. The fuses are cemented to the girders and the girders subjected to a constant-amplitude fatigue loading. Cracking of the fatigue fuses is monitored by checking electrical continuity across each fuse leg. Tests are continued until girder failure or until all fuse legs are broken and the mean fatigue life of the girder as predicted by AASHTO is reached. The breaking of the fuse legs is used to predict the fatigue life of each girder, which is then compared with the actual cycles to failure of the girder and the AASHTO mean life. The prediction gives satisfactory agreement with the AASHTO mean life in four of the tests. In two tests, the predictions vary significantly from the AASHTO mean life. Although several critical issues remain (such as adapting the fatigue fuse to the environment of a real bridge and conducting tests on a statistically valid sample), the results of this feasibility study indicate that the fuse could be a valuable tool for highway bridge inspection.

Publication Title

Transportation Research Record