Fracture Mechanics Prediction of Fatigue Life of Aluminum Highway Bridges
Søren Rom, Henning Agerskov

Abstract
Fracture mechanics prediction of the fatigue life of aluminum highway bridges under random loading is studied. The fatigue life of welded joints has been determined from fracture mechanics analyses and the results obtained have been compared with results from experimental investigations. The fatigue life of welded plate specimens has been investigated. Both the fracture mechanics analyses and the fatigue tests have been carried out using load histories, which correspond to one week's traffic loading, determined by means of strain gauge measurements on the deck structure of the Farø Bridges in Denmark. The results obtained from the fracture mechanics analyses show a significant difference between constant amplitude and variable amplitude results. Both the fracture mechanics analyses and the results of the fatigue tests carried out indicate that Miner's rule, which is normally used in the design against fatigue in aluminum bridges, may give results which are unconservative. Furthermore, it was in both investigations found that the validity of the results obtained from Miner's rule will depend on the distribution of the load history in tension and compression.

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