High-speed Train-track-bridge Coupled Vibration Under Seismic Excitations And Running Safety

The bridge is one of the important infrastructure and also one of the key technologies for railway construction. With the great development of high-speed railway, the proportion of bridges to the whole high-speed railway is improved on a large scale. The chance of running on the bridge for the high-speed train is increased when the earthquake occurs. When the train runs in a high speed, the dynamic action of the wheel/rail system and the bridge/track system is anabatic. Additionally, China is a country seriously affected by earthquake disasters with high-frequency seismic activity, intensity, light source and widely distributed. The possibility of derailment and overturning of vehicles coming up on the bridge has been greatly improved in the earthquake, and the earthquake poses a threat to the running safety of high-speed train on the bridge. Therefore, in order to establish and perfect the high-speed railway earthquake early warning system, and ensure the safe operation of high-speed railway, it is very necessary to carry out the research on the high-speed train-track-bridge system coupled vibration and traffic safety assessment under seismic excitations.In this dissertation, based on the bridge seismic theory and the dynamics throry of the whole railway system, combined with the related research achievements from the research team of the train-track-bridge coupled dynamics, the dynamic model of the high-speed train-track-bridge coupled system subjected to earthquakes is established. The corresponding analysis program is developed. The dynamic response characteristic of the high-speed train-track-bridge coupled system subjected to earthquakes is reasearched, the influence factors and the effects are summed up, and the running safety of train is analysed and evaluated. These research works provide a theory basis for the high-speed railway bridge seismic design and the earthquake early warning system design.Firstly, according to the dynamic modeling ideas and principles of train-track-bridge coupled system, the dynamic modles of vehicle, track and bridge are established respectively with the vibration differential equations. The four-axle vehicle dynamics model of the high-speed railway is set up with35degrees of freedom and the non-linear factors in vehicle suspension system are fully considered. The dynamics modles of the bi-block ballastless track, the discontinuous slab ballastless track and the track ballast track are also established. The bridge structure is modled by finite element method including space beam element, plate shell element et al. In the coupled model, based on the dynamic interaction principles of the train-track-bridge coupled system subjected to earquakes, the trains, tracks and bridges are regarded as a whole system, the wheel-rail interaction and the bridge-track interaction are regarded as relation and fully considered, the earthquake loads are treated as the external excitations and the acceleration input mode is adopted, the earthquake loads are directly be forced at the bottom of the bridge supporting points and its effect on bridge structure is produced by influence matrix, and then with the help of the wheel-rail interaction and the bridge-track interaction the dynamic responses of the whole coupled system are affected.Then, according to the interaction characteristics of the high-speed train-track-bridge coupled system subjected to earquakes, the mixed explicit implicit parallel algorithm for dynamic integration is adopt and the software VTBDYNA is developed. The theoretical result from VTBDYNA is validated by the SIMPACK software and the reliability and effectiveness of the software VTBDYNA is validated by comparing the calculation results with the field test results in Beijing-Tianjing intercity railway line and Wuhan-guangzhou high-speed railway line respectively.On this basis, a careful analysis of the dynamic response characteristics of the high-speed train-track-bridge coupled system subjected to uniform earthquakes is carried on. The influence laws of dynamic responses caused by many factors, including the speed, track irregularity excitation, earthquake intensity, seismic amplitude and frequency characteristics, and bridge structure type, are researched. These regularities are explained on the basis of the wheel-rail interaction and bridge-track interaction emphatically.Finally, focusing on the long-span continuous bridges in high-speed railway, by using the program VTBDYNA, the analysises of dynamic responses of the high-speed train-track-long-span bridge coupled system subjected to non-uniform earthquakes are worked out. The effects of the earthquake intensity, site type and traveling wave effect on the responses are discussed, and then the running safety is evaluated. At last, combined with the design conditions in this dissertation, the corresponding security domain is disscussed.