Overview of railway masonry bridges with a safety factor estimate

The European rail network includes a large number of masonry arch bridges for which the actual safety level is uncertain due to the rise in traffic demand and the material deterioration that have occurred since they have been built. For this study, a representative sample of 50 Italian large-span railway masonry arch bridges dating to the 19th and 20th centuries is selected. The sample includes single-span and multi-span bridges, shallow and deep arches, viaducts with slender and stocky piers, for which the geometric properties are taken from original design drawings and calculation reports. Despite such variability, the main structural characteristics and construction methods recur and comply with the design criteria suggested by historical treatises. The load-carrying capacity of the bridges and the corresponding safety factor with respect to rail traffic loads are assessed through a fiber beam based modeling approach. Safety levels are related to the shape of the arch, the height of the piers and the number of spans. Different constitutive assumptions are considered and the results of yield-design based methods are compared with those accounting for limited ductility of masonry in compression. The influence of uncertainties in the knowledge of geometric and mechanical parameters is also evaluated.