The influence of a train’s critical speed and rail discontinuity on the dynamic behavior of single-span steel bridges

In this paper, the influence of train speed on the dynamic behavior of lightweight steel bridges is studied. Moreover, an existing rail discontinuity is also considered and its combined effect on the dynamic behavior of the bridge is taken into account. In particular, this paper studies first the effect of the axis frequency on the bridge dynamic behavior as trains enter into the bridge span, which is coincident or almost coincident with the fundamental eigenfrequency of the bridge. This entrance frequency of the wheels obviously depends on the axis distance and the train’s speed. Secondly, a rail discontinuity is considered and its combined effect on the dynamic behavior of the bridge due to the developing impact forces is studied. The theoretical formulation presented herein is based on a continuous approach and the equations of motion of the bridge are determined through the use of a simple two-degrees-of-freedom model.