Development of supported rail vibration models
A rail model that allows practical track conditions to be taken into account is presented. This model is based on the semi-analytical finite element method which discretises the cross-section of the rail using conventional finite element method while including the vibration along the rail as travelling waves. Three rail support models are considered: one is based on an ad hoc approach which represents the track support as an equivalent layer of springs and the others model the rail support by masses and massless spring-dampers. All of the models are developed to be able to account for multiple layers of rail support, namely, rail pads, sleepers and ballast. The track support parameters, i.e. rail pad stiffness and damping, ballast stiffness and damping are measured in the field via an impact hammer test on a tangent track. The numerical results obtained indicate that the ad hoc approach and the lumped mass based models have equally good performance. The 2-node mass element based model is not able to reflect the correct rail vibration behaviour. The usage of mass elements introduces extra degrees-of-freedom and results in additional computation time compared to the equivalent spring based model. It is therefore recommended to use a combination of the ad hoc approach to model the track support and the semi-analytical finite element method to model the rail to investigate rail vibration response on a site-by-site basis.