Dynamic performance of concrete turnout bearers and sleepers in railway switches and crossings

With constant changes of geometry and alignment, wheel-rail forces, track and operational parameters, railway infrastructures are exposed to nonlinear actions by nature. A detrimental type of the loading condition that causes cracking in the railway concrete bearers in switches and crossings is the dynamic transient wheel force. The transient wheel forces are often due to the wheel-rail transfer over the dipped trajectory at a crossing nose. It is often found that most track deterioration incurs at the crossing panel. The turnout bearers crack and break. The ballast degradation then causes differential settlement and later aggravates impact forces acting on partial and unsupported sleepers and bearers. In addition, localised ballast breakages underneath any railseat increase the likelihood of centre-bound cracks in railway sleepers and bearers due to the unbalanced support. This paper investigates the dynamic performance of standard-gauge concrete bearers at crossing panel, taking into account the nonlinear tensionless nature of ballast support. A finite element model was established and calibrated using static and dynamic responses using past experimental results. In this paper, nonlinear phenomena due to topologic asymmetry on both sagging and hogging behaviours of crossing bearers are firstly highlighted. In addition, it is the first to demonstrate the effects of dynamic load impulses on the design consideration of turnout bearers in crossing panel. The outcome of this study will benefit the railway turnout design and maintenance criteria in order to improve train-turnout interaction and reduce maintenance costs.