Modelling of Tracks at Transition Zones: Analytical and Numerical Modelling Approach

Abstract

Rail track transitions are the discontinuities along the railway lines where conventional track adjoins the tunnels and bridges and are responsible for a sudden change in track structural properties. Frequent movement of fast passenger trains and heavy freights cause enhanced impact loads and differential settlements at these transitions that further lead to accelerated track degradation and increased maintenance costs. This paper presents a brief introduction to track transitions, the associated problems, and their causes and explains the occurrence of differential settlement at track transitions through analytical and numerical (2D FEM) modelling approaches. The stiffness effect on track settlement response under train loading is investigated, considering an Euler-Bernoulli beam on elastic foundation (BOEF). Vertical displacements of the track are calculated for various track stiffness values under train wheel loading (P = 10 tonnes). The results proved that the stiffer tracks undergo lesser settlements than the softer tracks. The effect of sudden stiffness variation is investigated by considering a one-step track transition where the stiffness suddenly changes from 80 MN/m (slab track) to 5 MN/m (ballast track). The results show that the settlement on ballasted track is almost 12 times greater than those on the slab track resulting in a large differential settlement at track transition.