Load-Carrying Capacity Improvement and Seismic Upgrading of a 1914 Riveted Steel Bridge

This paper describes the analyses carried out to evaluate and improve the load-bearing capacity of an old riveted steel bridge located in the Province of Perugia, in the central part of Italy. The bridge was designed and constructed between 1914 and 1918 to carry pedestrian and light vehicle loads, well below the current transportation requirements. It is composed of two steel spans with three continuous truss beams and of three masonry arches with an overall length of 116 m. The metallic part of the bridge rests on two unreinforced concrete abutments and on a pier, also made of unreinforced concrete, built inside the Tiber riverbed. A detailed study of the assemblage of the riveted steel elements put in evidence instability problems that had caused a partial buckling in a lower chord close to the inner support. Furthermore, the actual support system, composed of fixed bearings on the central pier and longitudinal sliding bearings on the abutments, concentrates the longitudinal seismic forces on the central pier which is unable to carry relevant horizontal loads. In this paper, the works carried out to increase the admissible traffic load and those to improve the behaviour of the bridge under seismic actions are briefly described.