Numerical investigation of railway transition zones stiffened with auxiliary rails

Culverts and bridges are the most common areas on railway lines where abrupt changes of track stiffness can occur. Using auxiliary rails in the transition zone is one option for gradually increasing track stiffness. The study reported in this paper investigated this issue by means of finite-element modelling. A ballasted track with a concrete culvert on the Tehran-Isfahan high-speed railway line in Iran was modelled and the effect of installing auxiliary rails in the transition zone was investigated. The ballasted track and its components - including railpads, ballast and subgrade were modelled as a series of mass-spring-damper systems, while the sleepers and culvert were simulated using Euler-Bernoulli beam elements. The dynamic behaviour of the track and its components was investigated by simulating loads moving at different speeds. The results indicated there was a reduced variation in rail deflections, track accelerations and railpad forces, demonstrating that auxiliary rails improve the dynamic performance and behaviour of transition zones.