Evaluation of the influence of coupling beam modeling of railway bridges on structural accelerations during high-speed traffic

Abstract

The discrepancy between vibrations measured on railway bridge structures and those predicted by calculations reveals the insufficient modeling depth of simple calculation models. Simple models often omit beneficial influences in favor of computationally efficient and easy-to-handle methods with few required input parameters. More realistic results can be obtained by considering, for example, interaction dynamics between the train masses, superstructure, and supporting structure. With this, precise knowledge of the coupling properties of the interacting elements is central as they significantly influence the calculated vibrations. This contribution focuses on the influence of modeling the bridge structures as coupling beams, i.e., by considering them as two vertically coupled beams representing the track (rails and sleepers) and the supporting structure. Both beams are connected vertically by Kelvin-Voigt elements, whose stiffness and damping properties reflect those of the ballast superstructure. A computational parameter study is carried out with a Railjet over a wide range of realistic combinations of single-span girder bridge characteristics. The calculated accelerations are subsequently compared with those of a reference simple beam model. Evaluating the results enables identifying the structural properties for which applying coupling beam models has a particularly significant influence on the maximum accelerations and quantifying that influence. Additionally, vehicle-bridge interaction effects are considered by applying additional damping. The analyses demonstrate the potential for obtaining lower acceleration results by considering the load-distributing impact of the ballast superstructure in coupling beam models. These findings open up the possibility of formulating structure-dependent recommendations concerning the targeted application of more complex modeling of the structure (coupling beam model) on the one hand and train (multi-body model) on the other.