Study On The Vertical Dynamic Characteristics Of The Longitudinal Connected Ballastless Track On Bridge

With the rapid development of passenger dedicated lines in China, ballastless track which is with the characteristics of higher stability, less maintenance and relatively mature technique, has developed rapidly. During the "11th Five-Year Plan", China will witness a building of passenger dedicated line amounted to 9800km.This is undoubtedly a huge construction task, and also a historic opport-unityto promote technological advancement of the high-speed railway in China. The building of passenger dedicated lines during the "11th Five-Year Plan" is of largescale and high standard. Due to ballastless track's inherent advantages,it has been widely applied to this construction.To develop bllastless track at this stage in China, the major developing ideaisto introduce the advanced technology from abroad and study the essence of it for further innovation. The major study of this paper is longitudinal connected ballastless track. To have an in-depth understanding of this new bllastless track, the paper evaluates the dynamic properties of this new bllastless track stru-cture in multi-manners.The studying method is to establish the modal analysis model,and the vehicle- track-bridge coupling system dynamic model of the long-itudinalconnected ballastless track by finite element software ABAQUS in this paper.First, based on the modal analysis of longitudinal connected ballastless trackmodel, some results can be obtained such as top 10 bands natural frequency of vibration and the respective modes as well as the effect of track parameters on the self-oscillation. Second, Based on the dynamic model of longitudinal conne-cted ballastless track, dynamic response under Test-axis and different parameters are studied primarily. At last, a high speed vehicle-ballastless track-bridge coupl-ing dynamic system model is built to analyze the vertical dynamic property of the system under the conditions of various speed.Through above analysis, conclusions can be drawn as follows: With the mo-dal analysis of the longitudinal connected ballastless track structure, we find that the first four frequency bands of the model is caused by the substructure of bridge. This is because of the reason that the stiffness of the substructure is smaller than that of the superstructure of the bridge and rail; While the stiffnessoffastener increases, the wheel-rail force as well as vibration response of rail, track plates, base and bridge also increase. But when the stiffness ranges from 25KN/mm to 50KN/mm, the increase margin is small, while from to 70KN/mm, this growth is significant. So the value of fastener stiffness of 50KN/mm is re-asonable; the thickness of the track slab can be reduced properly if it meets thedesign strength, such as 200mm. The effect of elastic modulus of track slab on vertical dynamic property can be almost negligible. However, in order to ensure the strength of the track slab, its elastic modulus values cannot be too small; theimpact of traffic speed on the longitudinal connected ballastless track on bridge is relatively large, and as the speed of the train increases, the vertical vibrationacceleration of rail, slab and bridge has substantially increased, but the changes of the displacement is small. These conclusions will be helpful for design of onbridge longitudinal connected ballastless track structure and provide a theoretical basis.