Numerical investigations of structure-soil-structure interaction in buildings

The influence of structure-soil-structure interaction (SSSI) in low- to medium-rise buildings is investigated through numerical simulations, and observations are compared with those from previous studies that analyzed data from a set of centrifuge experiments of similar models. The buildings include a one-story moment-resisting frame building on spread footings and a two-story shear wall building on a basemat. The numerical simulations are performed using the industry-standard, frequency-domain, linear analysis code SASSI, and the time-domain nonlinear finite-element analysis code, LS-DYNA. In LS-DYNA the simulations are performed with and without geometric nonlinearities (gapping, sliding and uplift) to understand their effects on SSSI. Three plan arrangements of the buildings are considered to characterize the influence of relative location on SSSI: (1) an in-plane SSSI (iSSSI) arrangement, in which the two buildings are placed adjacent to each other along a line parallel to the direction of ground shaking, (2) an anti-plane arrangement (aSSSI), in which the two buildings are placed adjacent to each other along a line perpendicular to the direction of ground shaking, and (3) a combined in-plane-anti-plane (cSSSI) arrangement, in which two shear wall buildings are placed at two adjacent sides of the frame building on footings. Results from the numerical simulations in SASSI and LS-DYNA show that SSSI has negligible effect on the global spectral accelerations of the buildings in these arrangements. The numerical simulations agree with experimental observations in this regard. Numerical investigations into the SSSI response of the frame building on footings placed adjacent to a deep basement show that the presence of the deep basement reduces uplift in the footings and results in smaller peak spectral accelerations at the roof, underscoring the potential importance of geometric nonlinearities (gapping, sliding and uplift) in SSSI and foundation design.