REHABILITATION OF STEEL RAILWAY BRIDGES BY IMPLEMENTATION OF UHPFRC DECK

Nowadays on the existing railway infrastructures many bridges can be found that have been built more than 50 years ago, and which were not designed for current loads and high speed trains. These are mainly bridges from hot rolled steel or cast iron and connected with rivets. The main idea of strengthening existing steel bridges is considering the possibility of adding load bearing deck above the main girders without replacing them. Converting alone metal section to composite cross-section raises the centre of gravity so that section can handle additional loads. In addition, the concrete deck may stiffen upper steel flange and thus eliminates the problem of stability of compressed part of the cross-section. In this paper the research on innovative rehabilitation method for the existing steel bridges is presented. The research has been performed within FP7 SMART RAIL project, and is based on the case study of rehabilitation project of the small non-ballasted steel bridge. The selected bridge ("Buna" bridge in Croatia) was built in 1893, with the first reconstruction in 1953. Since the steel structure of the old Buna Bridge had to be completely replaced, the bridge was dismantled and transported to the laboratory for the experimental assessment and development of the new rehabilitation method. The new design is based on the implementation of the prefabricated ultra-high performance fibre reinforced concrete (UHPFRC) deck. It is expected that this strengthened cross-section will be able to withstand the increased load, as required by contemporary regulations.