Efficient progressive global-local fatigue assessment methodology for existing metallic railway bridges

Abstract

This paper presents an integrated fatigue analysis methodology for existing metallic railway bridges, progressively implementing global to local fatigue assessment methods, each requiring a different level of calculation detail. The former are adopted mainly for screening the fatigue-critical connections using nominal stress-based SN curves, which often oversimplify the characteristics of the loading transference mechanisms, relying on high safety factors. On the other hand, the latter methods are innovatively proposed to refine the fatigue evaluation of connections that present unsatisfactory remaining fatigue life according to the global assessment. A multiscale modelling is adopted, leveraged by modal superposition concepts for structural analysis, which allows efficiently bridging the difference between the scale related to the overall size of the bridge and the local one associated with the fatigue damage developed at hot-spots (e.g., rivet holes). A real case study is investigated to demonstrate the added value of the innovative and efficient progressive fatigue assessment of details that would otherwise not be accurately analysed, taking into account the local characteristics of the response, if only common global procedures were implemented.