Idealized steady state interaction between railway vehicle and track

There are two types of distinct periodic dynamic waves in the history of the wheel/rail contact force. The first is caused by the variation in overall track stiffness owing to the effect of tie spacing. The second is caused by the travelling motion of the wheel and the oscillations of discrete supports, In the present train speed range these dynamic forces are usually less than 5 per cent of the static load, except that the coupled wheel/track resonant frequencies are excited at some speeds. The resonant forces due to discrete supports may be larger than 5 per cent of the static load in some cases. The magnitude of the resonant force mainly depends on the unsprung mass, tie spacing, vehicle primary and track ballast damping, rail stiffness and the stiffness on each support.