Dynamic interaction between a lumped mass vehicle and a discretely supported continuous rail track

This paper describes the formulation and application of a numerical model that simulates the vertical dynamic interaction between a train vehicle and the rail track. The considered vehicle model is supported on two double-axle bogies at each end and is described as a 10-degree-of-freedom lumped mass system comprising the vehicle body mass and its moment of inertia, the two bogie masses and their moments of inertia, and four wheelset unsprung masses. The bogie sideframe mass is linked with the wheel unsprung mass through the primary suspension springs and linked with the vehicle body mass through the secondary suspension springs. In the track model, the rail is treated as an infinitely long beam discretely supported at rail/sleeper junctions by a series of springs, dampers and masses representing the elasticity and damping effects of the rail pads, the ballast, and the subgrade, respectively. Shear springs and dampers are also introduced between the ballast masses to model the shear coupling effects in the ballast. The mass, stiffness and damping values of these track components and the sleeper spacings can be arbitrarily varied, so that variations in track component properties and track geometric errors can be taken into account. The dynamic interaction between the wheelsets and the rail is accomplished by using the non-linear Hertzian theory. Example applications of the model are given. (C) 1997 Elsevier Science Ltd.