Probabilistic fatigue models for bridge evaluation

Efficient evaluation of existing bridges requires knowledge of the parameters of resistance and load. This paper develops fatigue load models using weigh-in-motion (WIM) technology and strain histories. A ten girder, three simple span, two lane steel girder bridge was instrumented for all data collection. The bridge is located on US23, a major route between Detroit, Michigan and Toledo, Ohio. Vehicle static weight statistics are collected simultaneously with dynamic strain data. Theoretical strains are generated from static truck weight statistics and compared to the measured dynamic strains. Fatigue reliability analysis is reviewed and a fatigue load model is presented. From this analysis, conclusions are drawn regarding stress histories of the girders and importance of girder position in the bridge.