Probabilistic Assessment of the Equilibrium of a Steel Railway Bridge Based on Wind Tunnel and Traffic Records

Abstract

The European railway network includes many steel truss girder bridges, often dating back to the end of the nineteenth century. Assessment by the partial factor method according to Eurocodes often reveals insufficient reliability of these bridges. In particular, they fail to satisfy the equilibrium limit state when a strong wind occurs simultaneously with an unloaded train crossing the bridge. To avoid unnecessary structural interventions and expensive traffic restrictions, representative types of these bridges are tested in a wind tunnel to refine the force coefficients of wind pressure for the specific shape of the bridge and selected types of lightweight train. The values of force coefficients based on wind tunnel tests correspond to 70–80% of those provided in EN 1991–1–4. Traffic flow records for the railway line under consideration are then utilised to obtain distributions of weights and heights of lightweight trains. Detailed probabilistic analysis focused on a long-span truss bridge with an intermediate bridge deck demonstrates that the reliability of this bridge is close to the target reliability level when wind tunnel force coefficients are considered along with site-specific free-field wind and railway traffic records.