Parametric analysis and quantitative study on the influence of structure cluster on ground motion

This study conducted the parametric and quantitative analysis of the influence of soil-structure cluster interaction (SSCI) on ground motion. Based on the results of the shaking table test and numerical simulation, the changes in the characteristics of ground motion with the alterations of multiple factors are explored via wavelet packet decomposition. The results indicated that: (a) structure cluster reduces the site eigenfrequency, thereby amplifying the low-frequency components of ground motion and attenuating the high-frequency components. Ground can capture more of the high-frequency seismic energy coming from the bedrock through the long piles; (b) homogeneous structures inhibit the ground motion component with a frequency close to the structural eigenfrequency. The effect is more significant with increasing the number of structures and is gradually transformed into the energy dissipation effect acted in the wideband with increasing the damping ratio of structures; (c) the peak ground acceleration gradually diminishes from the center of the homogeneous structure cluster outward and this spatial variation is more pronounced under the excitation with high-frequency seismic waves. Furthermore, the energy variation index and coefficient of variation are employed to quantify the influence of SSCI on ground motion. The mass density of the structure cluster is the crucial variable for affecting the holistic variation of free-field ground motion. The spatial variation of ground motion attenuates significantly with increasing the thickness, shear wave velocity of subsoil, structural spacing, and homogeneity of structure cluster. The spacing between the structures required for the degeneration of SSCI into soil-structure interaction is chiefly related to the site condition and the structural frequency, which is enlarged with the decrease in soil shear wave velocity and structural frequency.