Seismic Interactions among Multiple Structures Founded on Liquefiable Soils in a City Block

Buildings are often located in close proximity to each other in urban settings. Seismic structure-soil-structure interaction near two adjacent buildings (${\mathrm{SSSI}}_2$) on liquefiable soils has previously been investigated and shown to be consequential. However, these studies did not evaluate the impact of multiple ${\mathrm{SSSI}}_{3+}$ (exceeding three buildings in a cluster) on key engineering demand parameters (EDPs). In this paper, we systematically explore the influence of ${\mathrm{SSSI}}_{3+}$, building spacing (S) in relation to width (W), arrangement, and location in a larger cluster on building EDPs. ${\mathrm{SSSI}}_{3+}$ is shown to reduce the foundation’s average settlement compared to an isolated structure (SSI) or even two adjacent structures (${\mathrm{SSSI}}_2$). Similar to ${\mathrm{SSSI}}_2$, however, ${\mathrm{SSSI}}_{3+}$ notably amplifies the permanent rotation of side or corner structures compared to an isolated counterpart or the neighboring center structure(s). The resultant tilt magnitude of corner structures experiencing ${\mathrm{SSSI}}_{3+}$ is greater than those under ${\mathrm{SSSI}}_2$ at $\mathrm{S}/\mathrm{W}<0.3$, while a slight reduction is observed for ${\mathrm{SSSI}}_{3+}$ at greater spacings ($0.3<\mathrm{S}/\mathrm{W}<1$). These rotations cannot be captured in a model of SSI or ${\mathrm{SSSI}}_2$. In all models considered, the direction and magnitude of flexural drifts within the superstructure are shown to depend on the orientation and magnitude of foundation rotation, which are themselves sensitive to building spacing and cluster arrangement. Overall, the numerical sensitivity study presented in this paper shows that ${\mathrm{SSSI}}_{3+}$ can adversely influence the performance and damage potential of corner or side structure-foundation systems compared to more simplistic cases of SSI and ${\mathrm{SSSI}}_2$ at $\mathrm{S}/\mathrm{W}<0.3$, which should be considered particularly for L- or square-shape cluster configurations.