Application of a three-dimensional isolation platform with semi-active control for the shaking table control room in the National Facility for Earthquake Engineering Simulation

Abstract The large shaking table of the National Facility for Earthquake Engineering Simulation (NFEES) of Tianjin University in China, with the table size of 20 m × 16 m and full load capacity of 1,350 t, is the currently existing largest earthquake simulation shaking table in the world. The control room of the shaking table generally experiences excessive vibration during the operation of the shaking table. To protect the control and data recording devices and satisfy the researchers’ comfort in the control room, a three-dimensional isolation platform with semi-active control is proposed and constructed. To deal with the potential resonance problem caused by the wide-band shaking table vibration, a frequency-dependent variable damping semi-active control method is proposed considering the frequency uncertainty. The vibration propagation characteristics from the shaking table to the control room is discussed and the control effect of the isolation platform is studied through site experiment under different vibration conditions. The results show that the designed isolation platform has an average isolation efficiency of 84.6%, 59.4% and 73.2% in the two horizontal and vertical directions, respectively. The average Z-vibration level is reduced from 98.89 dB to 86.20 dB which satisfied the standard for human comfort. The semi-active control function of the isolation platform on vibrations with different frequency characteristics has also been verified.