ANALYSIS OF TRACK-BRIDGE INTERACTION PHENOMENON IN INDIAN ENVIRONMENT

Abstract

Long Welded Rails/continuous Rails has now become synonymous with modern track structure for better comfort and safety, now the point to be discussed is what will be the effect of continuation of this LWRJCWR over the Bridges, being Indian Railways is one of the largest networks of railways having thousands of bridges along its entire network. In European countries UIC (774-3R) code is available to deal with this phenomenon. Unfortunately no such code is available in India and UIC code is not suitable for Indian condition. This has made necessary to investigate the safety of continuous tracks lying on bridges. Consequently it has become important to estimate additional horizontal reactions on bridge bearing, additional bending stresses in tracks and additional displacements due to track-bridge interaction. Interaction between track and bridge, i.e. the consequences of the behavior of one on the behavior of the other, occurs because track and bridge are inter liked, this interaction takes the form of forces in rails and its bearings, as well as displacement of the various elements of the bridge and track. If the interaction is under control then, then the bridge will continue to fulfill its function, i.e. supporting the track with out track being subjected to anomalies. The track and bridge were modeled by the beam elements, ballast, fastenings are modeled by using spring elements and the concept of beam on elastic foundation is incorporated in the model by providing a closely spaced springs. In model preparation general guide lines of Euro code, ERRI, UIC (774-3R) and LWR manual of Indian railways are incorporated, the model is validated with all ready existing model of the UIC (774-3R). In the Analysis load cases considered are thermal, breaking or acceleration and vertical loading by using appropriate load models and the results are tabulated. The parameters considered are longitudinal stiffness of track in approaches; stiffness of ballast and sleepers; stiffness of support of bridge which includes stiffness of piers; cross sectional area of rails; types of loading and deck length. In the analysis, rails have been considered to be continuous from approach to approach across the bridge. The stiffness of various elements has been taken with in their practical range adopted by Indian Railways LWR Manual. The modeling for this phenomenon has to be done in F. E.M. (finite element method) based software STAAD-PRO. By applying boundary conditions to the structure as a whole and solves the problem.