Assessment procedure and rehabilitation of riveted railway girders: the Campasso Bridge

The assessment and reclassification procedure of the Campasso Bridge, a 90-years old steel bridge typical of the beginning of the last century, is discussed in this paper. Steel is given a chemical and mechanical characterization on the basis of in situ and laboratory tests; a detailed survey of material degradation outlined the critical points of the structure and severe reductions of the resisting cross sections in several parts of the bridge. A load tests on the bridge, with accurate measurements of the displacements, allows the validation of the theoretical model showing that, due to the dimensions of the nodes, the truss is better represented by a 3D frame rather than a 3D truss beam. The high level of redundancy of both the structure and the joints make the bridge safe also according to the modern concepts of safety; specific railway limits to the Serviceability Limit States make the traffic to be limited to one rail only before re-opening the bridge to traffic. The skewness of the bridge (approx. 45°) asks for the torsional stiffness to be preserved by appropriate retrofitting works. Some considerations on fatigue limits show that the structure might be kept in service for not less than 20 years