Analytical representations of inherent structural irregularities in turnout crossing with moveable point

The inherent structural irregularities in turnouts are an impact source during train passing. The position of the wheel–rail contact point on the rails and the wheel trajectory can help reveal the characteristics of such structural irregularities. In this work, for a given nominal turnout, several parameterised single harmonic-shaped functions are selected as analytical representations to describe the inherent structural irregularities in a crossing with moveable point using multiobjective optimisation. The objective of the optimisation is achieved by ensuring that the responses of the analytical representation applied to a plain track are close to those of the turnout model under the constraint of maximum and minimum wheel–rail contact forces as well as a correlation coefficient. Thus, a plain track with irregularity functions can be considered an equivalent model to enable a fast modelling procedure and efficient assessment of vehicles. For a robust design in different traffic situations, two stochastic variables, namely the rail pad stiffness and axle load, are selected and are found to be significant. The influence of the random distributions of the input parameters on the statistical outputs of the wheel–rail contact forces is assessed using a descriptive sampling technique for several stochastic realizations.