Discrete model for SSSI between critical structures under strong ground motion

Usually, buildings in urban areas are designed by considering the response of structures in isolation i.e. a single structure, with no neighbouring structures. However, the existence of a high density of buildings in large cities inevitably results in the possibility of seismic interaction of adjacent buildings through the underlying soil that can produce an increase or decrease in seismic risk. Critical and important closely spaced structures, such as found in Nuclear power plants, are distinctly vulnerable to dynamic interaction, which should mandate full nonlinear SSSI analyses. In this study, we evaluated the effects of nonlinear Structure-Soil-Structure Interaction (SSSI) between two different buildings. A two-dimensional simple discrete nonlinear model is proposed that is described by a set of nonlinear differential equations of motion. The soil profile directly underneath foundation is modelled as a nonlinear phenomenological Bouc-Wen model and rotational interaction spring between buildings are assumed. We use an EC8 spectrum matched ground motion record. The Reweighted Volterra Series Algorithm (RVSA) is employed for the matching process. The results showed that there are unfavourable configurations of the two buildings that can produce important differences between nonlinear SSSI and nonlinear SSI. In the same way, it is demonstrated that the adverse effects of SSSI can be more pronounced when the nonlinear is considered.