Residual Life Assessment of Steel Truss Bridge due to Coupled Action of Corrosion and Fatigue

Abstract Steel trusses have often been used as medium to long-span railway-over-bridge structures due to their rapid installation and reliable performance. However, fatigue reduces the service life of these steel bridges. Rapid stress reversals are generated in steel bridges due to the high-speed movement of trains. The damage is further intensified with aging of the structure, due to corrosion. This coupled action of corrosion and rapid stress reversals increase the stress concentration in steel bridges, especially in the vicinity of existing initial defects. Thus, the focus of the current study is to develop a relationship between the residual fatigue life and the coupled deterioration due to corrosion and rail loads, provided in standard railway design guidelines. For the present study, a 63m railway-over-bridge structure modeled in professional design and analysis software is subjected to eleven 25t rail loads taken from Research Designs and Standards Organisation (RDSO) guidelines. The rainflow-counting algorithm has been used to convert critical member’s stress histories into an equivalent set of constant amplitude stress reversals. The obtained equivalent stress histories are applied to the critical member of the steel bridges exclusively modeled using ANSYS. From the numerical results obtained, the residual fatigue life is calculated in terms of number of equivalent sets of varying stress reversal that the simulated member can withstand before failure.