Experimental study of a new kind of double‐layer shaking table

Abstract Existing large‐scale electrohydraulic shaking tables (EHSTs) have limited frequency bandwidth because of the capacity of electrohydraulic systems. Here we propose a double‐layer shaking table (DLST) which is capable of generating excitations over a wide band of frequencies. The lower table is a conventional EHST with a long‐stroke actuator which can generate low‐frequency excitations. The upper table is fixed atop the lower table, and equipped with a short‐stroke actuator which can generate high‐frequency excitations. The FFT/IFFT signal separation process, three‐variable control algorithm, and feedforward compensation technique are employed to control the shaking table. The two tables are controlled simultaneously to ensure the upper table reproduces ground motions over a wide frequency bandwidth. A series of experiments were performed on a unidirectional DLST. The results suggest that the DLST can successfully reproduce excitations over a wide band of frequencies, and demonstrate that the proposed control methods are effective. The control procedure in which the upper table tracks the full‐frequency signal to compensate for the tracking errors of the lower table is recommended.