Study on the torsion and sway responses of a massless rigid foundation excited by spatial obliquely incident P-waves considering the nonlinearity of the surrounding soil

In this study, the influences of the spatial incidence angles of P-waves and soil nonlinearity on the soil–structure interaction system are investigated. A finite element model of the SSI system is developed using the equivalent nodal force method, viscoelastic artificial boundary, and the revised Davidenkov model to analyze the dynamic responses of a rectangular foundation and its associated structure. The results indicate that the rectangular foundation predominantly exhibits sway responses to spatially oblique incidence P-waves, with a negligible torsion response. Compared with vertically incident P-waves, spatially oblique incident P-waves significantly increase the maximum sway and torsional angles of structural floors. Furthermore, soil nonlinearity increases the sway angle of the foundation and intensifies the maximum torsional and sway responses of the floors. Therefore, soil nonlinearity and the spatial incidence angles of P-waves need to be considered in structural seismic hazard assessments.