Dynamic Analysis Of The Transition Section Between Floating Slab And Monolithic Track Under Different Damage Conditions

In metro lines,the steel spring floating slab track is often used as the vibration reduction track for the sections with special vibration reduction requirements,and the ordinary monolithic ballast track is still used for the other sections.So the transition of floating slab-monolithic track bed occurs at the transition point,which will cause a sudden change in the overall stiffness of track system,further increase the vibration response of vehicle track,and have a negative impact on the safe operation of subway track.In this paper,a two-dimensional dynamic model of train-track-lining-foundation system is established in the transition zone.Compile MATLAB numerical solution program and separately analyze the influence of track transition structure type,differential settlement of transition section and support failure of transition section on the dynamic response of train-track system.The main research contents and innovations are as follows:(1)The theoretical model for train-track system in the transition zone between the floating slab track and the monolithic bed track is established,in which the effects of tunnel lining and the foundation are considered.According to the basic principle of track dynamics,the vehicle-track coupling dynamic equation is derived,and the vehicle-track dynamic response is calculated by MATLAB programming.(2)The influence of the stiffness of steel springs and fasteners on the vibration response of the train-track system is studied under the condition of track transition.Selecting the appropriate supporting element as the stiffness changing element of track transition section,and studying the influence of steel spring's stepped stiffness increasing at track transition.(3)The transition model of metro track under differential settlement is established.and a cosine function is introduced to simulate the distribution curve of the tunnel differential settlement.The vibration responses under different settlement positions and settlement waveforms are calculated.Finally,combined with the requirements of metro safe operation,some suggestions are provided for the safe operation of trains.(4)The transition model of metro track considering the failure of fasteners and springs are also established in this paper.The effects of the quantity and location of the failure fasteners and springs on the response of train-rail system are studied.The suggestions for the safety of metro operation are offered based on the metro code and the limit value of rail deflection change rate.