Analysis of dynamic behaviour under traffic loads of a strengthened old steel bridge

Abstract

The bridge over Mures river situated on the county road DJ 707A at Km. 1+271, near Savarsin, was built in 1897 as a steel structure with four span of 39,8 m. length. All spans were designed in a constructive art typical from historical period of XX-the century begin: the main truss girder with parabolic upper chord and downward cross stud, longitudinal and transverse floor beams (stringers and cross girders) at lower chord, a ZORÉS profiled deck covered by road’s system and lower and partially upper wind bracings. In figure 1 is presented the general view of bridge and in figure 2 some pictures of old structure.
Due to the bridge’s geometrical dimensions which don’t satisfy the present conditions of side clearance it has arranged with road user to assure a single 4,0 m. width running way, which let run also the tractor-allied equipments and farm implements, and two 1,0 m. width pedestrian way near each main girder, separated from running way by a kerb and security sliding carriages.
Inside a co-operation with TU München-Lehrstul für Baumechanik, the proposed strengthened structure has been analysed concerning the dynamic behaviour [2] under traffic loads. The analysis was accomplished with FEM, utilising MSC-NASTRAN program and the simulation with PRESIM 98, an oriented computer program created at TUM, in the aim to simulate the effect of a truck’s going over the bridge.
After input data computing has resulted, step by step, the knot’s deplacement and stresses in structure elements and after Excel full-automatic processing, it has obtained the diagrams, like in figure 10, which shown, on time dependence, the dynamic effect.
Since both the vehicle and the roadway were idealistically regarded and, no differences were observed.