Zur Einspannwirkung von Eisenbahngleisen - Die Auswirkung auf die erste Biegeeigenfrequenz bei Einfeldträgerbrücken

Restraining effects of railway tracks on fundamental frequencies of single-span bridges

Capacity and serviceability design of high-speed railway bridges often requires comparison of relevant eigenfrequencies of the superstructure to frequencies resulting from periodic excitation by crossing axles. If the eigenfrequencies are calculated, quality of results depends on assumptions made in modelling, sometimes resulting in large differences between calculated and real eigenfrequencies.
Though contribution of railway tracks overlapping bridge ends to system rigidity is well known and can be modeled with non-linear longitudinal spring elements connecting track and superstructure top edge or track and embankment, often simply supported beam models are used. This article derives horizontal substitutional springs to represent unloaded embankments with ballast, which incorporate the calculation of rotational springs. When modelling single-span systems with beam or plate elements, rotational springs at bearings can represent the restraining effects of tracks.
Furthermore a simplified method can be used to calculate the fundamental frequency n0 considering the contribution of rotational springs. The method is used on the calculation of n0 of real filler beam bridges with ballast superstructure and obtained results are compared to measured values and threshold values for simplified resonance check for velocities up to 200 km/h.