Investigation on the sensitive and insensitive zones of the rail support stiffness for the dynamic response of a vehicle system under low excitation frequencies

The variation of the rail support stiffness is an inherent issue of railway tracks. There is still no consensus on the influence of the rail support stiffness variation on the dynamic response of the vehicle–track system. One view indicates that changes of the support stiffness do not have considerable influence on the vehicle dynamic response. The main influence factor is the rail deflection. However, the opposite view presents that the influence of the support stiffness on the system dynamic response is obvious. Reasons that lead to the dispute of previous studies are the neglect of the influence of the excitation frequencies and a lack of understanding of stiffness sensitive zones. In this study a vehicle–track coupling model with equivalent overall support stiffness is employed to investigate the response of the vehicle to changes of the track stiffness and excitation frequencies. Results show that for each of frequencies (1–40?Hz) the dynamic response of the vehicle is only sensitive to a certain range of the support stiffness. A stiffness sensitive zone for each excitation frequency can be observed. In order to further study the influence of the subgrade on the vehicle system dynamic response a vehicle–track-subgrade model is utilised. The subgrade stiffness belonging to the stiffness sensitive zone has a significant influence on vehicle vibrations. For overall support stiffness of the rail higher than 20?kN/mm, the stiffness sensitive zones of low excitation frequencies can be avoided.