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

Abstract

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.

Simulation of spatially varying ground motion of urban buildings based on wavelet packet neural network

“…In general, the ground motion slightly weakens from the center of the structure cluster radially and this variation becomes more significant with a higher-frequency seismic excitation when only the effect of structural relative position is considered. 26 It is explained by the fact that the variation of the radiation damping and the dispersion of high-frequency components within heterogeneous mediums. This effect is negligible for the seismic response of the structural principal mode.…”

“…According to Refs. 25 and 26, it can be found that the disturbance of the adjacent structure to the target structure presents a monotone attenuation with the increase in the foundation spacing, and the disturbance radius is related to the structural period and shear wave velocity of subsoil. Therefore, the range of the coefficient ( η ) is defined from 0 to 1 as shown in Equation (), and its value is attenuated by the increase in the spacing between the target structure and the adjacent structure.…”

“…Even if a massive structure is nearby and it possesses a significant effect on the ground motion of the target structure, the stopband offset caused by the structural damage is also not evident due to it is mostly a long‐period structure. Thirdly, the structural damping ratio (1% –25%, see Section 3.3 in Ref. 26) has a significant effect on only the main components of ground motion in which the signal energy is attenuated with the increase in the structural damping ratio. Taking all the above influences into consideration, for the surrogate model without considering the structural nonlinear behavior, the obtained seismic damage results of structures are safe and reliable when the modulated ground motions are applied to the urban seismic damage simulation.…”

“…It is helpful to simplify the logical operation of the surrogate model and make higher application feasibility for that in urban seismic damage assessment practice. In the research work conducted by the authors previously, 25,26 the influential mechanism of SSCI on ground motion was discussed, and the relevant influential parameters were quantitatively analyzed, including the scale, frequency, damping ratio, configuration, height, and density of structure cluster, structural relative position, pile dimension, spectral features of seismic wave, and site condition. The results of the existing work indicate that the characteristics of ground motion are affected by SSCI of two different forms which occur synchronously.…”

“…In this case, the superstructure acts as a tuned mass damper that affects the ground motion of the foundation, this phenomenon was introduced in detail in Ref. 26. As shown in Figure 2, m 1 , k 1 , c 1 represent the mass, lateral stiffness (it is related to the shear wave velocity and thickness of subsoil), and damping of the subsoil in the simplified dynamical system, m 2 , k 2 , c 2 are the mass, lateral stiffness, and damping of the superstructure.…”