On railway track receptance

Abstract

Railway track dynamic stiffness is the relationship between track deflection and loading frequency. Its inverse, also known as receptance, is an important quantity that affects the track’s dynamic response under moving trains and noise and vibration characteristics. Despite its importance, there has been limited detailed study into receptance at lower frequencies (<1000Hz). Thus, this paper contributes two main novelties. The first is the presentation of a novel numerical approach well-suited to receptance calculation, and secondly, a parametric study identifying the key frequencies associated with different track components. The new approach is first presented, which uses a 3D periodic domain coupled with perfectly matched layers and is solved in the frequency-wavenumber domain. It is well-suited to the problem because it can capture dynamic wave propagation within the complex geometries associated with each track component, while using an efficiently-sized domain. The model is validated in terms of its ability to capture the dynamic response of 3D periodic structures, and also the behaviour of a railway track. It is then used to study the effect of two common modelling assumptions (beam-on-elastic foundation and symmetry) on the calculation of track receptance. It’s shown that ignoring wave propagation in the subgrade-earthwork layers induces errors in the ≈80−300% range at frequencies below 200Hz, and errors of ≈30% in the 200−440Hz range. It is also shown that the assumption of track centreline symmetry ignores some track bending modes and can also introduce errors (≈20%) at frequencies up to 1000Hz. Finally, the effect of the most common ballasted track components on receptance are analysed and new knowledge is presented regarding the typical frequency ranges associated with each.