Seismic performance of advanced three-dimensional base-isolated nuclear structures in complex-layered sites

The application of three-dimensional (3D) base isolation for nuclear structures is advantageous. In this study, an advanced 3D base isolation technique was developed and the nonlinear seismic response of 3D base-isolated nuclear structures in complex layered sites was investigated using a global method. The study first designed a novel 3D isolation system, including horizontal and vertical isolation, based on the disc spring theory, which can flexibly adjust the structural stiffness and vertical bearing capacity. To verify the applicability of 3D base isolation, the dynamic behaviour of a 3D base-isolated nuclear island building in complex-layered sites subjected to beyond-design basis ground motion was investigated using a proposed high-precision simulation program of soil-structure interaction (SSI) based on the global method. The findings demonstrate that in complex-layered sites, the SSI increases the horizontal floor response spectra (FRS) but decreases the vertical FRS of 3D baseisolated nuclear power plants, and both the horizontal and vertical isolation rates remarkably decrease. The influence of the SSI becomes more evident as the intensity of the ground motion increases. The proposed 3D base isolation system exhibits excellent isolation effects. When the vertical stiffness is reduced, the vertical isolation effect becomes more significant. However, the adverse rocking motion of the island building should be effectively controlled. The research results support the practical application of 3D base isolation technology for nuclear structures located in complex-layered sites with high seismic intensities.