Research Of Power Flow Transfer Characteristics And Parameter Matching On Multi-layer Vibration Isolation System Of Viaduct Rail Transit

In recent years,urban viaduct rail has been developing vigorously in China.However,the vibration and noise generated by the train operation directly radiate to the environment,affecting the work and life of residents.Therefore,it is very important to research the vibration energy transfer characteristic of the viaduct line.Vibration reduction methods applied in track structure can effectively reduce vibration.However,most of the existing research ignore the constraints between different vibration isolation elements.This will cause the effectively isolated energy to accumulate in the upper part of a layer of subsystem,resulting in vibration and damage to the track structure or components.Power flow contains force,velocity,and phase information,and it describes the transfer relationship of internal vibration of the system from the perspective of energy,which provides a new idea for vibration isolation.In this thesis,the simple vibration isolation system and the multi-layer vibration isolation system of elevated track are analyzed based on the power flow method.The main research contents are as follows:1.The research results of viaduct rail vibration at home and abroad are summarized.Outline the modeling methods and control measures of track vibration and the research status of power flow theory,and then propose shortcomings in the research of viaduct rail vibration reduction.2.The transmission characteristics of power flow in single-layer vibration isolation system are studied.In a single-layer vibration isolation system,the variation of average input power with system parameters(stiffness or damping)is not consistent when the excitation frequency and system vibration isolation element parameters change simultaneously.In practice,according to the excitation frequency of the external load,the stiffness and damping of the system isolator can be reasonably adjusted to reduce the energy input to the system.3.The power flow transfer characteristics of the finite element models of the two-layer vibration isolation system and the three-layer vibration isolation system are studied.The results show that when the parameters of vibration isolation elements in a certain layer of the system change,it will not only affect the power flow input to this layer,but also affect the power flow input to other layers,but the influence on power flow from input to other layers is less than that of this layer.4.The validity of the multi-layer vibration isolation system model for elevated track is verified.The finite element model of the multi-layer vibration isolation system of viaduct rail is established to calculate the vibration acceleration response at all levels of the track when the train operations.And then the vibration characteristics of different layers of the straight section of a viaduct line in one city are tested on site.The result shows that the predominant frequency of rail vibration is 430–730Hz,the predominant frequencies of ballast vibration are 40–75 Hz and400–450 Hz,the excellent frequency of bridge vibration is 35–100 Hz.The vibration attenuation is about 18 d B from the rail to the track bed,and about 30 d B when further transmitted to the bridge.And the validity of the model is verified by comparing with the test results.5.Analyze the influence of viaduct rail structure parameters on energy distribution and transmission.A better matching method of fastener,track plate support and bridge support stiffness and damping is obtained based on the results.For example,the stiffness of the track plate support can be appropriately increased,together with a low stiffness fastener system to meet the higher vibration isolation requirements along the viaduct rail line.For the line with high vibration level requirements,the damping of track plate support can be appropriately increased,but it cannot be too large,or it is not conducive to the vibration reduction of high frequency excitation and matching the medium damping fastener system.The research results have reference significance for the design and selection of stiffness and damping of vibration isolation measures for actual rail transit viaduct lines.