ABSTRACT
A lot of steel bridges worldwide are encountering the threats imposed by fatigue. Fatigue, usually resulting from the stress cycles produced by operating vehicular loads, may lead to cracking, cross-section reduction, and even failure of bridge components. Dynamic stresses of the steel bridges due to vehicular loads (e.g., train or truck) provide vital information for fatigue evaluation, condition assessment, among others. Steel bridge decks offering the platform for rails generally experience intense vibrations induced by the moving trains. Accordingly excessive stress amplitude level and number of stress cycles can exist. Accurate dynamic stress analysis of steel decks paves the way to reliable evaluation of bridge fatigue behavior. This paper examines dynamic stresses of the fatigue-critical details in bridge decks using the coupled train-track-bridge system model. The system model consists of train model, track model, and bridge model constructed through advanced finite elements and multi-scale modelling techniques. The system model is capable of characterizing vibrations (e.g., displacement and acceleration) of local components in the bridge decks which are eventually proved as the most fatigue-prone details of the whole bridge. Subsequently, dynamic stresses at these details can be obtained based on the vibration results. The proposed methodology is illustrated on a steel railway bridge with an open deck system located in Beijing. Field test data from the real bridge are used to validate the efficiency of the approach. Analysis results demonstrate that the proposed methodology can yield dynamic stress histories of fatigue details in the bridge decks in both accurate and fast manners.
