Environmental impact of the vibration generated by the underwater shaking table of the National Facility for Earthquake Engineering Simulation (NFEES)

Earthquake simulation shaking tables serve as the valuable tools for investigating the seismic performance of structures, yet they can generate excessive vibrations in surrounding environments during operation. The National Facility for Earthquake Engineering Simulation (NFEES) in China, which is currently in the commissioning phase, will be the world's largest earthquake simulation research facility. Its experimental center consists of a 16 m × 16 m shaking table and two 6 m × 6 m underwater shaking tables (one movable). This study aims to investigate the environmental impact of the vibration generated by the fixed underwater shaking table. Initially, the vibrations of the surrounding ground, shaking table foundations, and adjacent simulation center are tested using the sinusoidal full-load and full-acceleration excitations generated by the shaking table. Upon analyzing the test results, it is observed that the peak ground acceleration (PGA) in the short side direction of foundation attenuates rapidly for high-frequency loading, with a maximum acceleration attenuation up to 55.95 % at distances of 0 m–20 m. The maximum acceleration of the foundation occurs at the edge of the shaking table and significant differences in acceleration are observed at various points across the foundation. The VLZmax of the simulation center is 66.85 dB, which is lower than the limit requirements of the Chinese standard GB55016. Subsequently, an overall finite element model of the surrounding soil-shaking table foundations-adjacent simulation center is established. Following the validation of the numerical model, the vibration isolation efficiency of the adjacent river course and the foundation isolation joint that separates the large shaking table foundation from the underwater shaking table foundation are assessed. Compared to the test results, numerical results show relatively minor discrepancies in the peak acceleration of the ground and the foundation, with maximum errors of 24.59 % and 21.11 %, respectively. The river course and the foundation isolation joint demonstrate better vibration isolation performance for short-wavelength waves, with a maximum vibration isolation efficiency reaching 64.71 % and 63.56 %, respectively.