Abstract

It is difficult to conduct shaking table tests that require large-displacement high-frequency seismic excitation due to the limited capacity of existing electrohydraulic servo systems. To address this problem, a double-layer shaking table (DLST) is proposed.

The DLST has two layers of one table each (i.e., an upper table and lower table) and aims at reproducing target seismic excitation on the upper table. The original signal is separated into two signals (i.e., a high-frequency signal and low-frequency signal) through a fast Fourier transform/inverse fast Fourier transform process, and these signals are applied to the two tables separately.

The actuators connected to different tables only need to generate large-displacement low-frequency or small-displacement high-frequency movements. The three-variable control method is used to generate large-displacement but low-frequency motion of the lower table and high-frequency but small-displacement motion of the upper table relative to the table beneath.

A series of simulations are carried out using MATLAB/Simulink. The simulation results suggest that the DLST can successfully generate large-displacement high-frequency excitation. The control strategy in which the lower table tracks the low-frequency signal and the upper table tracks the original signal is recommended.