Roadbed Z¨¹blin Track System Vertical Dynamic Response Study

With the rapid development of passenger dedicated lines and city mass transit in China, ballastless track which character is higher stability, less maintenance and mature technique was developed rapidly, it is necessary to analyze the dynamic properties of ballastless railways. This paper focuses on the ballastless track layed on the soil formation ,and the vehicle and Züblin ballastless track are viewed as a whole system, then the Züblin track and vehicle vertical coupling dynamic model is established.In this paper, Züblin ballastless track layed on the soil formation is separated as 20-degree of freedom finite element. The track between every adjacency two fastener is treated as an element, in which the rail is simulated as continuity-point-supporting Euler beam, the cushion of the rail (fastening system) is simulated as line spring and dampers, the BTS plate (track slab) and the HGT plate (the base of concrete) are viewed as rigid joint, simulated as the elastic plate, the subgrade is simulated as line-distributed-diaphragm-flexure and dampers. The vehicle is simulated as 6-freedom multi-body model. The equations describing the movement of the train-track-subgrade vertical vibration system are formulated on the basis of minimum potential theory and "sit in the right seat" principle, and simulating program is constructed accordingly.On the basis of the track vertical free vibration model, the free vibration of the Züblin ballastless track is analyzed in this paper by means of subspace iteration method. The vertical free vibration frequency and vibration mode between first to five steps are put forward, and the calculating results are proved to be correct and reliable. The free vibration analysis can check the correctness of the track vibration model.With the vertical track stepped irregularity which is belong to the ballastless track layed on the soil formation as the vertical vibrating resource, the train-Züblin ballastless track vertical vibratory responses are analyzed, and some time-history dynamic response curves of the system are put forward which manifest Züblin ballastless track layed on the soil formation structure dynamic characteristic.On the basis of the train-track model: The first a study of parameter work is processed, which is mainly about the effects of the spring stiffness of subgrade support, the thickness of the BTS plate and the two-block sleeper span on the wheel/rail force, vertical vibration displacement and acceleration of the train, the rail and BTS plate. The appropriate values of track system parameters are obtained. By comprehensively considering, the reasonable spring stiffness of subgrade support is 6×10~8～8×10~8N/m; the reasonable thickness of the BTS plate is 0.24m;the reasonable distance between the two-block sleeper is 0.6m-0.7m; the asymmetrical settlement of the subgrade should be limited to under 20mm/20m with speed of 200km/h and 10mm/20m with speed of 250km/h. This concludes are propitious to the Züblin ballastless track layed on the soil formation structures designing. The second, based on the considerations of safety and riding comfort ,the allowable limits for track irregularities with speed of 250km/h are proposed, including vertical profile irregularity ,cross-level irregularity, stepped irregularity and twist irregularity.24-degree of freedom ballast track model and 20-degree of freedom Züblin ballastless track model are established. The dynamic effect of the velocity of the vehicle is assayed, including the track stiffness ratio and the irregularities on the train/track system. The paper lists several types of transition remedies of the passenger dedicated lines in China.