Numerical analysis on dynamic behavior of articulated switch sleeper in turnout system under wheel load drop

Based on the numerical algorithm of a three-dimensional flexible joint element to furnish the stiffness and damping in transverse, vertical and rotational directions, a calculation model under wheel load drop according to the finite-element method is built, and, the dynamic responses in time and frequency domain are studied respectively for a whole turnout structure with articulated or integral switch sleepers impacted by a falling wheel-set, considering the nonlinear characteristic of the ballast's support under the sleepers as well as the special construction of the articulated joints. Compared with the normal integral sleeper design, the track with articulated switch sleepers has a lower rigidity, which changes more evenly along the track and improves its dynamic performance. Furthermore, by modifying the switch sleepers' vibration behaviour, the articulated joints effectively reduce the impact loading of the ballast at the end of the sleeper under the turnout branch track when the vehicles are running on the main turnout route. This will extend the life of the ballast bed. Finally, in combination with the articulated switch sleepers, high elastic fastenings, whose rational parameters are proposed, are employed to make up the elastic track foundation, the vibration characteristics of high-speed turnout are optimized.