Fatigue in Aluminum Highway Bridges under Random Loading
Søren Rom, Henning Agerskov

Abstract
Fatigue damage accumulation in aluminum highway bridges under random loading is studied. The fatigue life of welded joints has been determined both experimentally and from a fracture mechanics analysis. In the experimental part of the investigation, fatigue test series on welded plate test specimens have been carried through. The material that has been used has a 0.2% proof strength of 310 MPa and an ultimate tensile strength of 327 Mpa. 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 test series carried through show a significant difference between constant amplitude and variable amplitude fatigue test results. Both the fracture mechanics analysis and the fatigue test results indicate that Miner’s rule, which is normally used in the design against fatigue in aluminum bridges, may give results which are unconservative. 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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