Influence of 3D Urban Dense Building Groups on Magnification of Ground Motion in Homogeneous Sedimentary Basin

Abstract

By using the harmonic response analysis in the finite element analysis method, the seismic dynamic interaction of the three-dimensional urban building group-homogeneous sedimentary basin is studied. The viscoelastic artificial boundary is introduced, which can overcome both the defects of low-frequency drift and high-frequency instability, and the equivalent load in frequency domain is obtained by fast Fourier transform for loading, to explore the influence of the different incident frequencies (0.5–5.0 Hz), different numbers (196, 400, 676), and spacing (55 m, 62.5 m, 70 m) of building groups on the ground motion of homogeneous sedimentary basin under the incidence of SV wave. Numerical results illustrate that at low frequency, the displacement cloud image of the homogeneous sedimentary basin model shows an obvious phenomenon of “central focusing.” With the increase of frequency, the displacement cloud image gradually changes from “central focusing” to “multipoint focusing.” Meanwhile, the displacement peak gradually moves from the surface to the center of the basin. At a certain incident frequency, the existence of dense building groups will change the spatial distribution of displacement amplitude in the basin. Under the action of high-frequency incident waves, denser building groups with more buildings and smaller building spacing have a more pronounced weakening effect on the seismic response of homogeneous sedimentary basins. The displacement response of the center of the basin is generally large. When planning important buildings, the center area should be avoided as much as possible. For existing buildings, structural reinforcement is needed. It is of great significance for the planning and layout of buildings in the soft sedimentary basin and the reasonable spacing of buildings to reduce the risk of urban earthquake disaster.