The impact of local fatigue damage on bridge performance

Abstract

Fatigue is one of the main failure mechanisms for steel bridges and theoretically puts restrictions or limitations on their continued use. However, bridges are structures with redundancy to various extents. The appearance of a crack sometimes does not necessarily lead to the failure of the whole bridge and can be tolerated temporarily. Therefore, to maintain or extend the service life of bridges, an adequately selected criterion for assessment and an accurate assessment of the service life are both of great importance.

This paper aims to reveal how existing local fatigue damage influences the performance of the entire bridge. A simply supported steel railway bridge with four parallel main beams is selected as a case study. Various sizes of cracks are simulated close to mid-span in a finite element model. The maximum vertical displacement of the main structure is selected as the failure criterion, which is connected to material plasticity and restoration of initial conditions. The results show that, for the selected bridge, cracks close to the mid-span in one of the four beams will not lead to irreversible displacement, regardless of the crack size. No global plastic behavior has been initiated. It shows that with sufficient redundancy the existing fatigue damage will not influence the functionality or integrity of the whole bridge, and related actions can be planned with lower priority.