An experimental study of the influence of parapets on the aerodynamic loads under cross wind on a two-dimensional model of a railway vehicle on a bridge

Abstract

Aerodynamic loads on railway vehicles under cross winds are governed both by the shapes of the vehicles and of the surroundings. Apart from the inertial loads due to accelerations acting on the vehicle, aerodynamic loads due to cross winds are of paramount importance in the lateral equilibrium of the vehicle, in such a way that if the lateral wind speed becomes larger than a threshold value, overturning of the vehicle can take place. The degree of danger of overturning increases when the train is on a bridge, the reason being that the velocity in the atmospheric boundary layer grows as the height increases, leaving aside the fact that at ground level there may be other elements acting as windbreaks (mainly vegetation). The effects of different types of solid parapets on the side force and rolling moment acting on a 1/70 scale two-dimensional model of a typical high-speed train vehicle have been measured by wind-tunnel tests, both when the vehicle is placed on a bridge and when it is on ground. Experimental results show that, as one could expect, aerodynamic loads decrease as the height of the windbreak increases, and that solid parapets seem to be more effective on bridges than on ground.