A Model for Evaluating Long-Term Support Degradation at Railway Switches

A railway switch is characterised by movable parts, discontinuities in rail geometry and non-uniformities in trackbed stiffness. This work aims to assess the performance of railway switches considering long-term degradation of trackbed support with trafficking. A vehicle-track interaction model capable of reproducing the longitudinal variation in support stiffness and changes in contact condition through the switch panel is used. Site measurements of bearer deflection at a selected S&C are used to back-calculate a trackbed stiffness and initialise dynamic simulations to determine wheel-rail and trackbed contact forces. The calculated trackbed forces are used as an input in an iterative process to estimate the evolution of long-term rail top level and irregularity growth. The model results are compared with measured rail irregularity growth and the model is shown to predict similar trends. Model results and measurements show that higher rates of track geometry degradation occur around the load transfer area. The use of Under Sleeper Pads is found to decrease differential settlement within the panel.