Design And Research Of Floating Slab Vibration Isolator Based On Geometric Nonlinear Dynamics Theory

In recent years,with the rapid development of urban rail transit,more and more cities have carried out the construction of underground rail transit.The operation of underground rail transit makemakes the daily travel of urban residents more convenient,but the following problems such asare the vibration and noise caused by the operation of the subway,especially its vibration problem has not been effectively solved,which not only affects the surrounding buildings,but also brings inconvenience to the residents’ life and the use of precision instruments in the buildings.Aiming at this problem,floating slab track is introduced to isolate the vibration.Although the vibration attenuation effect of the floating slab track on the high frequency part is very obvious,there is the contradiction still exist contradiction between the vibration attenuation effect and the operation stability of the low frequency part still exists.Therefore,without affecting the supporting capacity of the floating slab track,the construction of a non-linear vibration isolation system with low-frequency vibration isolation effect performance is of great significance to solve the vibration problems caused by the operation of the subway.The main The force mechanism of the simplified floating slab track with steel spring is analyzed.According to the geometric nonlinear dynamics theory,the simplified singledegree-of-freedom spring-mass system is transformed into a nonlinear vibration isolation system.The static characteristics of the non-linear system are analyzed.By adjusting the geometric parameters,the system can show different stiffness characteristics,so as to solve the vibration isolation problem of the low frequency part of rack vibration reduction.Based on the train-rail simulation model,the external excitation of floating slab track,displacement response of floating slab and force response data transmitted to the foundation are extracted when a metro train passes by,combined with three different conditions of no-load,fixed load and overload.In order to reduce the flexibility of floating slab,the excitation spectrum and response spectrum obtained by simulation are weighted averagely to make them closer to the real value.The fourth-order Runge-Kutta method is used to optimize the key design parameters of the new non-linear vibration isolation system under three different working conditions.According to the actual construction demands of the project and the vibration displacement requirements of the subway operation,a variety of parameter schemes are calculated and screened with the response of the non-linear vibration isolation system as the objective under the condition of satisfying the space restriction demands.Sensitivity analysis of each parameter scheme is carried out to ensure that it can be realized in engineering.Then,the dynamic characteristics of the system are analyzed,and the periodic external excitation with constant excitation term is introduced.The multi-harmonic balance method is used to solve the nonlinear system,and the amplitude-frequency,phase-frequency relationship and the transmission rate curve of the system are obtained.According to the analytical results of the system under periodic excitation,the numerical results under fastener force excitation are verified.The simplified single-degree-of-freedom vibration isolation is modeled and analyzed by using simulation software.The errors of friction,contact stiffness,damping force and horizontal spring stiffness are taken into account.The simulation results and numerical results are compared and analyzed to verify the accuracy of the numerical results.Through the tunnel model,the vibration level of the tunnel wall is tested to verify the low frequency vibration reduction effect of the non-linear vibration isolation system.