| The rapid development of China’s high-speed railroad makes high-speed railroad bridges cover a large area of China’s seismic zone,high-speed operation of the train will inevitably earthquake when the bridge travel.The ballastless track system used in high-speed railroad bridges has a certain longitudinal stiffness,which changes the seismic response of the bridge and thus has an impact on the safety of trains running on high-speed railroad bridges under the action of earthquakes,so it is of great significance to study the safety of high-speed railroad bridges running under earthquakes considering track constraints.The main research contents of this paper are as follows:(1)To summarize the current research status of domestic and foreign scholars in two fields: the influence of track restraint on bridge seismic performance and earthquake vehicle-bridge coupling vibration.(2)A 20×32m multi-span simple-span girder bridge with CRTS II ballastless track system is used as the engineering background,and the complex line-bridge system is simplified based on the analysis of the interaction characteristics of each member.Bridge model and multi-span simply supported girder bridge model without considering the track constraint.(3)A 31-degree-of-freedom vehicle dynamics model based on SIMPACK software is developed,in which a parametric modeling approach is adopted to facilitate the adjustment of different models for subsequent studies.The Hertz nonlinear elastic contact theory to calculate the wheel-rail normal contact force,and the simplified Kalker theory and FASTSIM numerical calculation method to calculate the wheel-rail tangential contact force are introduced.And the establishment of the joint vehicle-line bridge simulation system is realized by the program interface of SIMPACK.(4)Seismic excitation with different peak seismic accelerations in longitudinal bridge direction and German low disturbance track unevenness excitation,both excitations are used as system excitation.Three indicators for evaluating the safety of train travel are analyzed.The influence characteristics of different peak seismic accelerations and different train travel speeds on the evaluation indexes of train safety travel in the two vehicle-bridge systems with or without considering the longitudinal stiffness constraint of ballastless track system are studied separately,and the train safety travel thresholds under the two systems are given separately.(5)By comparing and contrasting the thresholds of safe train operation under the two systems,the longitudinal stiffness constraint of CRTS II slab ballastless track system can improve the thresholds of safe train operation on high-speed railroad bridges under earthquake action. |
