Numerical Analysis of the Dynamic Response of Existing Railway Bridges.

The railway is an important part of the infrastructure in todays society and there is a need to increase the capacity and verify the existing railway network to face the challenges of tomorrow. To meet todays and the future demand set upon the railway network, there is a need to strengthen and assess the condition of existing railway bridges. This thesis focuses on numerical analysis of the dynamic response of railway bridges. First, viscous damping models are considered since they represent an important part of the dynamic properties of the bridge. Then the moving load problem is investigated, and studies on the dynamic response of a simply supported beam under different load models are conducted to determine the qualitative difference between the moving force, moving mass and the sprung mass model. The resonance phenomena induced by the moving loads are also considered. Finally, a case study is presented where the dynamic properties and behavior the Tallerås railway bridge is determined by establishing a three dimensional finite element model of the bridge in the finite element code Abaqus. The results show that the difference between the load models are the level of inertia effects included and the amount of energy dissipated by the load model. The case study indicate that resonance effects induced in the Tallerås railway bridge is due to the repeated loading from railway axles. The results also show that it is important to include the track in dynamic analysis of steel truss bridges. The thesis finishes by suggesting suitable subjects for further work