Dynamic Response And Environmental Vibration Influence Of Floating Slab Track Based On Rubber Nonlinear Characteristics

Rubber floating slab track is widely used in engineering due to its higher damping effect and cost performance.As a kind of polymer material,the accurate description of the nonlinear mechanical behavior of rubber pad will directly affect the results of dynamic simulation.Therefore,the research goal of this paper is to carry out dynamic response analysis of vehicles and tracks on the basis of accurately describing the nonlinear mechanical characteristics of rubber mats,and then to predict and evaluate the vibration of surrounding soil and building environment.In this paper,the rubber floating slab track was taken as a research object in metro vibration damping track.Firstly,the Mooney-Rivlin superelastic and Prony series viscoelastic constitutive models of rubber pad were determined according to relevant literature and theoretical dates,and the key parameters were deduced so that importing the numerical values into the simulation software.Secondly,the vehicle-track coupled transient dynamic model and the steady-state dynamic model of harmonic response in floating slab track were established.Then this paper analyzed the influence of the superelastic and viscoelastic characteristics of the rubber pad on the vehicle dynamic parameters,the vibration characteristics and propagation law of the track structure.Finally,a 3d coupled environmental vibration prediction model of vehicle-track-tunnel-soil-building was established based on the finite element method,and the vibration level distribution and propagation law of the vibration were analyzed in soil and building considering the superelasticity and viscoelasticity of rubber pad.The main contents and conclusions are as follows:(1)From the perspective of vehicle dynamics parameters,the stability of the car body degrading when considering superelasticity of rubber pad,in which the vertical vibration acceleration of the car body increases by 17%at most.However,the operating safety of the vehicle has little change,in which the vertical force of the wheel and rail increases by 4%at most.From the perspective of track dynamic parameters,the vibration acceleration of each track structure changes obviously when considering superelasticity of rubber pad.The vibration acceleration of the rail increases by about 16%,the vibration acceleration of the floating plate decreases by 11%at most,and the vibration of the base increases by nearly two times.The vertical displacements of rail and floating slab are significantly reduced.Under the static stiffness of 0.019N/mm~3 of the rubber pad,the vertical displacements of rail and floating plate are decreased by 12.5%and 34.0%respectively.The transmission loss and insertion loss of track structure considering the rubber superelasticity are all lower than the loss under linear elasticity,in which the maximum difference of transmission loss is 6d B and the maximum difference of insertion loss is 3.19d B.(2)When considering the viscoelastic characteristics of rubber pad,the peak values and corresponding frequencies all increase of each order of frequency response curves of rail,floating plate and base under the same static stiffness of rubber pad.Considering the viscoelastic characteristics of rubber pad,the peak value of admittance and dynamic flexibility of the rail increased by 37%and 25%respectively.Meanwhile,the peak values of the floating plate are increased by 55%and 39%respectively under the static stiffness of 0.019N/mm~3 of the rubber pad.Considering the viscoelastic characteristics of rubber pad,the structural vibration decay rate is slightly higher than that of linear elastic condition in the frequency range of 1-30Hz.However,in the frequency range of 40-80Hz,the structural vibration decay rate is significantly lower than that of linear elastic condition,and the vibration is more difficult to decay along the longitudinal direction.(3)The main frequency of soil vibration is 20-40Hz.The soil vibration increases first and then decreases along the direction of soil depth,and the largest soil vibration occur as depth as the tunnel.Meanwhile,the vibration of surface soil has an obvious amplification trend due to the influence of surface soil quality and Rayleigh wave.The maximum Z vibration level at the tunnel depth is 77.80d B,and the maximum Z vibration level at the surface is 72.7d B at 6m away from the tunnel center line.When the vibration propagates on the surface,the peak value of vibration acceleration decreases first and then increases and decreases with the increase of horizontal distance,and there is an obvious vibration amplification phenomenon.(4)With the increase of floors,the vertical vibration in building slabs decreases first and then increases.The average Z vibration level of the first floor and the top floor is68d B,while the average Z vibration level of the third to fourth floors is 61d B.Compared with the vibration in the building plate,the vibration at the connection point of the building beam and column is significantly reduced,and the vertical vibration acceleration is reduced by about 50%on average.From the perspective of the maximum vibration level of frequency division and the Z vibration level,it is reduced by 4-5d B at the same floor compared with the vibration in the building plate.With the increase of floors,the vibration at the beam-column joints decreases first and then increases.After the 10th floor,the vibration level increases slowly,and the maximum Z vibration level appears at the top floor,which is about 63.6d B.For the same floor,different building area positions and different structure forms still have certain influence on the peak vibration acceleration,the maximum frequency division vibration level and the weighted Z-vibration level due to the difference of the overall stiffness of the structure.