STABILITY AND STRENGTH PROBLEMS ASSOCIATED WITH TRACK BRIDGE INTERACTION

Abstract

The increase in speed of trains on the Indian Railways calls for the use of continuous welded rail (CWR) due to its low maintenance cost and avoidance of fractures and increased service life of track and vehicle components. The support of the track by an engineering structure such as a bridge a constitutes a special situation. Here, the interaction between track and supporting structure cannot be neglected. Additional Longitudinal rail forces are caused by uniform temperature change of the A bridge deck, acceleration and braking of trains and bending under vertical load of the supporting structure. On the other side, with the introduction of continuous welded rail (CWR), there evolved new challenges including the derailing disasters associated with track buckling due to high compressive stress. The track stability may be affected due to excessive relative displacements between ballast bed and the sleepers and the accompanied reduction in the effective frictional resistance. For high-speed tracks, however, solving these problems by introducing rail expansion devices in the track is not a feasible and attractive solution as these devices may result in a local discontinuity in the vertical track stifthess and track geometry which demands intensive track maintenance. The study aims at developing a method for simplified computer analysis that can be executed by available commercial software using problem specific parameters. A parametric study is performed using SAP2000, a F.E.M (Finite element method) based software, to compute the effects of different actions such as temperature variation, braking loads, and vertical loads on, rail stresses, support reactions and track displacements. This report discusses the continuous welded rail (CWR), Track-bridge interaction phenomenon, Continuing CWR / LWR over bridges, numerical modelling and numerical studies on Track-bridge interaction phenomenon.