The Effect of Thin-Layer Elements in Structural Modeling of Rail-Track Supporting System

A conventional track system consists of rails, sleepers, ballast, sub-ballast and sub-grade. A track foundation on the basis of live load response and permanent settlement, it is necessary to use an analytical model that will realistically represent the actual behaviour of this track system subjected to actual load. This study deals with the development of numerical modeling of Malaysian railway track along with the supporting system. The model is capable to simulate the sleeper, ballast, sub-ballast, soil layers and their interaction as a single compatible unit. Under plane strain condition, the coupled finite-infinite elements were implemented to represent the near field and far field behaviour of media. Thin-layer elements have been used to represent the interfacial behaviour between sleepers and ballast. The following constitutive relationships were adopted in this study: (i)-Linear Elastic (ii)-Elasto-plastic Based on the above physical and material modeling, an existing two dimensional finite element program has been extensively modified in view of including the new elements as well as the new constitutive law. After verification of the modified version of the program, the applicability of the program was shown in analysis of railway track supporting system. The response of the railway track supporting system has been presented under static and dynamic loading. The behavior of the railway track supporting media has been discussed with respect to displacements, accelerations and rate of plastic flow. This analysis shows that the thin layer element is reliable to be used as an interface element to represent the contact surface between two different materials