Considerations on longitudinal dynamic effects of unbraked vehicle in passenger train composition – parametric study

Abstract

The study investigates the trains’ longitudinal dynamic evolutions in certain unusual situations that may be encountered, even rarely, in railway operation. It is about the case of operating passenger trains having in componence a vehicle with isolated braking system. This is a state that, according to regulations, is generally not acceptable, but there are circumstances that can conduct to exceptions. Our purpose is to find out by numerical simulations the influence that certain parameters, such as the number of vehicles of the train, the weight of locomotive and the position of the unbraked vehicle, have on the longitudinal dynamics of passenger trains during braking actions. The numerical simulations were performed for trains in classical composition, meaning a locomotive hauling 3 up to 19 passenger vehicles, thus covering virtually all the current situations encountered in operation. In simulations there were considered all the possible placements of the unbraked vehicle within the train body. The main outcomes, submitted to a comprehensive analyse, are the maximum in-train forces and the position in long of the train of the most affected couplers by longitudinal dynamic compression (buff) and tensile (draft) forces. The time dependency of in-train forces is also discussed.