Anti-seismic And Vibration Isolation Study On A Nonlinear System With Quasi-zero Stiffness

In recent years,with the development of science and technology in our country,the size,quality and precision of the equipment have been continuously improved.In particular,the transformer substation of the national grid is an important lifeline project of each province and city.The stability of the operation of such equipment under earthquake disaster can be directly determine the difficulty of disaster relief and reconstruction.In order to minimize the secondary disaster risk caused by the paralysis of the power system caused by the earthquake,the anti-seismic facilities of the existing substation are difficult to meet the demand.Most of the current transformer isolation measures are based on linear vibration isolation theory,but because of its isolation capacity is often negatively correlated with its carrying capacity,and the low frequency signal produced by the earthquake often does not have the attenuation effect but will produce amplification phenomenon,and thus it cannot achieve the isolation effect of large high voltage and ultrahigh voltage transformer.Therefore,without changing the bearing capacity of the vibration isolation system,the structure with good low frequency vibration isolation performance,that is,the structure with high static stiffness and low dynamic stiffness,has important significance in the isolation engineering.In this paper,based on the definition of the quasi-zero-stiffness system and the stable quasi-zero stiffness system,the definition of the multi-degree-of-freedom quasi-zero stiffness system and the multi-degree-of-freedom stabilized quasi-zero stiffness system are given.Based on the SD oscillator system with quasi-zero stiffness,the three-degreeof-freedom vibration isolation structure with quasi-zero stiffness is constructed by threedimensional infinite coupling.The parameters configuration conditions and the characteristics of the global stiffness distribution under different parameters are given.The single-degree-of-freedom and multi-degree-of-freedom damped forced vibration systems are constructed by introducing unidirectional,multi-directional cofrequency and multi-directional equal-frequency periodic excitation.The system is analyzed by averaging method and harmonic balance method respectively.The frequency response characteristics and the force transmission rate characteristics are analyzed in detail,and compared with the linear vibration isolation theory,based on the transmission rate curve on the system damping ratio of the fixed point given vibration isolation system low frequency vibration performance evaluation indicators,further analyzing and comparing the quasi-zero-stiffness vibration isolation system's low frequency vibration isolation performance.Combined with the actual engineering requirements,the measured seismic wave acceleration spectrum is introduced as the system external excitation,and the numerical method is used to analyze the system's acceleration response and the relative displacement response peak under different parameter configuration conditions,and the optimal parameter configuration scheme of the quasi-zero-stiffness isolation system is given.Based on this scheme,the response of the system under the action of seismic wave is analyzed,and the comparing the acceleration response peak value and the average value with the vibration isolation ratio of the linear vibration isolation system is analyzed respectively.Further analysis of the quasi-zero stiffness vibration isolation system and the linear vibration isolation system the frequency domain response under excitation to verify the theoretical analysis of the system,the isolation performance of its detailed analysis and demonstration.The results show that the quasi-zero stiffness vibration isolation system has better performance improvement than the linear system in seismic isolation from the response peak value,average value or effective vibration isolation frequency to ensure the stability of the transformer under the action of seismic waves.