Abstract Summary
The reliability of railway bridges is significantly influenced by so-called resonance states that appear in case the excitation frequency of the passing train is close to one of the natural frequencies of the railway bridge. In these resonant conditions, the dynamic response of the bridge is significantly increased, which can lead to higher maintenance costs, reduced passing speeds, and in the worst case, derailment of the train. In particular, the ballast of railway bridges significantly influences the response behaviour and should be take into account when evaluating the structural responses. In the proposed contribution, the influence of ballast behaviour on the structural responses in the state of resonance is of predominant interest. This includes the influence on the response peak at resonance and the resonance speed, i.e. the train speed at which the state of resonance appears. Three different railway bridge models are utilized in order to determine the influence of the ballast bed on the acceleration and displacement response of railway bridges subjected to high-speed trains. In the context of the finite element method, the ballast bed and track superstructure are implemented using linear or nonlinear dashpot and spring elements. The passing trains are modelled as moving single forces representing the static axle loads of a train. A reduced order modelling approach is utilized in order to significantly reduce the analysis time of the computationally demanding 2D finite element time history response analyses. Based on the evaluated so-called response spectra, consisting of absolute peak acceleration and displacement responses of the railway bridge for different train speeds, the resonant states are identified and the influence of nonlinear ballast behaviour is discussed and contrasted.
