<p>At least 20% of existing railway bridges in Sweden are reinforced concrete (RC) trough bridge that consist in a slab carried by two longitudinal main beams. As these bridges are getting old, there is an urging need to assess their remaining capacity with the aim of prolonging their service lives. The limited literature on the topic has pointed out that there is a significant difference between the capacity predicted by available codes and that obtained experimentally. In this paper, a review of the Bridge and Tunnel Management database (BaTMan) of railway infrastructure in Sweden, is carried out to gain an overview of the current state of the Swedish railway bridge, with focus on trough bridges. Then, a non-linear finite element model is calibrated using the experimental results of the previous testing of a decommissioned trough bridge. The model is used in a parametric study where the effect of key mechanical parameters on the capacity of trough bridges is studied.</p>

In Sweden, a substantial amount of railway bridges is approaching their intended lifespans and are planned to be replaced. However, it is not sustainable neither from a financial nor an environmental perspective to replace these bridges if they are still sound and safe. Thus, an evaluation of their actual capacity is required with the aim of extending their lifespans. A way to obtain a more accurate capacity is to determine the loads that are acting on them. Available literature points out the lack of experimental investigations on sleeper-ballast contact pressure, as well as on the stress distribution along and across the ballast. Consequently, railway bridge design has been based on traditional rather than rational assumptions, which can be quite conservative. In this paper, a review of models is carried out for evaluating stress patterns on the surface of the slab on ballasted concrete bridges. Then, a simplified finite element model of a concrete trough bridge, a common type of structure in Sweden, is used in a parametric analysis aimed to understand how the identified pressure distribution patterns affect the performance of this type of structure. Finally, with the purpose of studying how some parameters influence the bridge safety, a probabilistic reliability analysis is used. The reliability index beta ( ) is obtained using the polynomial response surface method and its value is compared for different boundary condition scenarios. Also, the sensitivity factors for the considered random variables are compared and analyzed. Results show that the assumption of support condition and pressure pattern has a significant impact on the capacity, failure mode and probability of failure of this type of structure.