Nonlinear simulation of vertical behavior of railway fastening system

Rail fastening system plays an important role in safety of railway tracks. Despite proven nonlinear mechanical behavior of this system, it has been simulated as a linear spring-dashpot element in the current practice. Discussing this limitation, a nonlinear spring-dashpot element for simulation of vertical behavior of railway fastening system was developed in this study. For this purpose, influences of fastening stiffness, frequency of load and magnitude of preload (as the main influencing parameters) on the mechanical behavior of fastening system were investigated through parametric analyses of fastening systems. To this end, a finite element model of fastening system was developed and validated in this study. Using the results obtained, nonlinear mathematical expressions for the stiffness and damping of fastening systems were derived. The results led to propose a new technique for mathematical simulation/modeling of railway fastening system. Comparison of the results obtained from railway track models with and without consideration of the new simulation technique indicates a considerable improvement (60% in average(in accuracy of theoretical results with the use of nonlinear models. Based on the results obtained, the conditions, in which linear simulation of fastening system provides reasonably accurate results, were derived and discussed.