Dynamic Numerical Analysis of a Railway Bridge-Embankment Transition Zone

Railway transition zones represent one of the most critical sections of the railway infrastructure, where the contrast in stiffness between the embankment and the structure often induces differential settlements and irregular load transfer. These discontinuities alter the dynamic response of the system, which can significantly affect both passenger comfort and the long-term performance of the track. Understanding these mechanisms is essential for predicting the behaviour of geotechnical systems subjected to repeated train loading and for developing effective mitigation and monitoring strategies. This study presents a numerical investigation of the vertical accelerations experienced by the sleepers and the train components as the vehicle passes over a bridge-embankment interface affected by differential settlement. Using a three-dimensional finite element model, it was possible to simulate the coupled behaviour of the embankment, track, and bridge under dynamic loading. Several scenarios were analysed by varying train speed, subgrade stiffness, and the magnitude of the imposed settlement. The results highlight the strong influence of these parameters on the amplification of vertical accelerations, particularly near the interface between the embankment and the bridge abutment. The study also discusses the implications of these findings for predicting track degradation and assessing ride quality. The acceleration results obtained provide useful indicators for identifying critical areas within transition zones and for defining targeted strategies for the installation of monitoring systems. Overall, the work contributes to a deeper understanding of the dynamic behaviour of railway transition zones and supports the development of predictive tools for their long-term performance assessment.