Finite element analysis of a crossing panel under dynamic moving load – effect of support conditions and implications on foot fatigue

The dynamic behaviour of a complete crossing panel under a transient moving load is considered using finite element method (FEM). A 3D model is developed in ANSYS software and validated using recent field measurements data from the UK. Four assumptions of trackbed stiffness distribution are tested. The best matching assumption to the field measurements is suggested and taken forward in the current study. Vibration modes are classified by comparing the modal and transient analysis results in frequency domain based on physical interpretation of the modes. A comparison is made between the so-called ‘P2’ dynamic force value in the current study and that calculated by Jenkin’s formula as specified in the UK Network Rail standard NR/L2/TRK/012 relating to crossing fatigue calculation. It is shown that this standard over-estimates the P2 dynamic force. The crossing stress results are presented and the most critical point on the foot, where the stress is considered to be in the elastic domain is introduced, in relation to the various support conditions. It is concluded that approximating the dynamics load with an equivalent P2 force envelope is sufficient to capture peak stresses for foot fatigue analyses. Finally, two scenarios for modelling hanging bearer effects are analysed in terms of foot stresses. Considering 5mm initial gap at three consecutive bearers leads to a significant 40% increase in stress value.