Experimental analysis of damping mechanisms in ballasted track on single-track railway bridges

Abstract

The calculated dynamic behaviour of railway bridges during high-speed traffic differs from the actual behaviour of its bearing structure. In the case of steel railway bridges, dynamic calculations often overestimate the actual vibration responses and therefore lead to uneconomical results. This gap between calculation and measurement constitutes a complex research issue, whereat the consideration of the ballasted track in dynamic calculations has a major influence. Concerning the ballasted track there is a broad range of various mechanical models with different levels of detail and complexity and also widely differing related characteristic values. However, the consideration of its damping and stiffness characteristics in dynamic calculations still entail uncertainties. This paper focuses on the analysis of different damping mechanisms which occur in the ballasted track. The research is based on a large-scale test facility which allows to quantify the ballasted track’s damping and stiffness properties. Concerning the damping properties, the ballasted track shows a predominant frequency dependency and a subdominant displacement dependency, whereby different energy dissipation mechanisms occur under different circumstances. With regard to the stiffness properties, the ballasted track displays a clearly non-linear behaviour contrary to the specifications given in the technical standards. Furthermore, if tested under clearly specified conditions, the ballasted track can even undergo a change toward a liquid state, thereby completely losing its stiffness properties.