Numerical study of soil-structure interaction of railway bridges using simple mechanical models

In this master thesis, the influence of the soil-structure interaction of railway bridges on their dynamic vibration response during the passage of high-speed trains is investigated and the influence of various parameters is evaluated. A holistic view of the dynamic interaction system with its essential components train, track, bridge and soil is taken. The parameter study of the soil-structure interaction is carried out for bridges made of reinforced concrete and steel with different span widths, as well as for varying stiffness modulus of the soil and varying bedding stiffness of the track. Two different models are used for the train, to study their dynamic impact on the structure at different speeds. The analyses are based on the simplified mechanical model of König et al. (2021), which considers all the necessary parameters of the physical problem. The first analyses are carried out within the framework of a preliminary study. In this first study, the interaction system consisting of bridge and soil is considered and the modal parameters, equivalent damping coefficients and natural frequencies of the bridge-soil interaction model are determined. The results of this preliminary study are intended to show the dependence of the damping coefficients and the natural frequencies on to the span width, the construction material of the bridge, the stiffness modulus of the soil and to illustrate the influence of the foundation mass. Following the preliminary study, a parameter study of the dynamic soil-bridge-train-track interaction system is conducted. The resulting dynamic vibration response of the bridge is investigated in more detail using a single-load model (SLM) and a mass-spring-damper system (MSD) of the train. Furthermore, the influence of the bedding stiffness of the track is addressed. The evaluation of the obtained results with the model of König et al. (2021) is carried out with regard to the dynamic deflection and acceleration of the bridge structures in form of response spectra. The results of this parameter study allow a more precise statement about the response behavior of bridges under dynamic train loading can be made.

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