Research On Three-Dimensional Isolation And Semi-Active Control For Floors Under Shaking Table Vibration

With the expansion of the construction scale of the shaking table,the model test capacity of the shaking table can reach more than 1000 tons at present,and the reaction force of the actuators can reach more than 2000 tons.The reaction force of the actuator excites the vibration of the shaking table foundation,and causes the vibration of the shaking table laboratory and surrounding buildings through the transmission of vibrations in the soil.Because of different test purposes and the scale of the test model,the amplitude and frequency of the ground motion loading are uncertain.In the case of shaking table vibration,the traditional passive vibration reduction and isolation technology still have limitations.In this paper,a semi-active control algorithm based on real-time frequency detection is proposed,and based on this,a semi-active controlled three-dimensional(3D)floor isolation system is established,which can be used for the isolation of vibrations of the floors in laboratories and surrounding buildings in the vibration environment of the shaking table.The main contents of this paper are as follows:(1)A semi-active controlled three-dimensional floor isolation system is proposed which contains a 3D isolation subsystem,a semi-active control subsystem and a floating floor subsystem.The 3D isolation subsystem is established by setting up vertical spiral springs to realize the 3D isolation function.(2)An on-off control strategy based on real-time frequency detection is proposed,and a window method is established to detect the dominant frequency of the input vibration.Based on the strategy and method,the proposed semi-active controlled threedimensional floor isolation system is capable to switch to large damping mode in the resonance range and small damping mode in out of the resonance range,which enables an optimal control among wide frequency band of input vibration.(3)The vibration isolation effect of the proposed semi-active controlled threedimensional floor isolation system under different control parameters and loading conditions is compared through the shaking table test,and its effectiveness is verified.The acceleration transmissibility ratio is 0.8-1.2 under sinusoidal motion,and 0.4-1.2under earthquake caused vibration.(4)The mathematical model and Simulink calculation model of a RC frame structure with semi-active control are established.The calculation results show that the acceleration reduction ratio(maximum acceleration with control to maximum acceleration without control)in the horizontal and vertical directions is in the range of0.36-1.05 and 0.35-0.49 respectively for the floor isolation system,and 0.33-0.72 and0.15-0.89 respectively for the base isolation system.