Asymmetrical influences on nonlinear dynamics of railway turnout bearers

By nature, railway infrastructure is nonlinear, evidenced by its behaviors, geometry and alignment, wheel-rail contact and operational parameters such as tractive efforts. It is noted that most train-track interaction models do not consider appropriate behaviour of ballast over time. In fact, the ballast degradation causes differential settlement and impact forces acting on partial and unsupported tracks. Especially at switch and crossing areas, the aggressive dynamic train-turnout interaction often damages the supporting components such as turnout bearers and fastening systems. This paper presents a nonlinear finite element model of a standard-gauge concrete bearer in a turnout system, taking into account the tensionless nature of ballast support. The finite element model was calibrated using static and dynamic responses in the past. In this paper, the influences of topologic asymmetry on both dynamic sagging and hogging behaviours of sleepers under impulse loading are firstly highlighted. In addition, it is the first to demonstrate the effects of asymmetrical length on the nonlinear dynamic behaviour of the turnout bearers. The outcome of this study will improve the rail construction criteria in order to adjust support profile and appropriately mitigate bearer/ballast interaction. It will help improve the structural health monitoring strategy, enriching an intelligent track system.