Train-induced vibrations on urban metro and tram turnouts

In contrast to standard track, where train-induced vibrations are mainly related to track irregularities, the dynamic response of turnouts is dominated by the nonuniform geometry of wheel-rail contact and variations in track flexibility. Such peculiarities are responsible for the development of strong vibrations during train passage. At the point of rail intersection (heart), where a gap is unavoidable to provide the necessary wheel flange clearance, the system is subjected to severe impact loading, critical for the design and maintenance of railway tracks. Especially in the case of urban turnouts, the vibration levels are also directly related to the exerted noise nuisance. This paper presents two analysis methods to simulate train-turnout interaction. The first is based on a multibody model of the trainset and of wheel-rail contact, utilizing a simplified finite element model for the turnout. The second focuses on the details of the turnout, which is modeled with three-dimensional finite elements, utilizing a simplified model to compute impact loading due to wheel passage over the flange-way gap. The two models are validated against line measurements on three different urban metro and tram networks. A parametric analysis is conducted to investigate the role of soil-structure interaction, which is shown be important for the dynamic response of the system.