Dynamic structure-soil-structure interaction for nuclear power plants

Abstract

The paper explores the linear and nonlinear dynamic interaction between the reactor and the auxiliary buildings of an idealized Nuclear Power Plant (NPP) on a realistic layered soil profile, aiming to exemplify the significance of structure–soil–structure interaction (SSSI) modelling in designing or re-evaluating critical structures, such as NPPs. Based on realistic geometrical assumptions, high-fidelity 3D finite element (FE) models of increasing sophistication are created in the Real-ESSI Simulator. Starting with elastic soil conditions and assuming tied soil–foundation interfaces, it is shown that the rocking vibration mode of the soil–reactor building system is amplified by the presence of the auxiliary building through a detrimental out-of-phase rotational interaction mechanism. Adding nonlinear interfaces, which allow for soil–foundation detachment during seismic shaking, introduces higher excitation frequencies (above 10 Hz) in the foundation of the reactor building, leading to amplification effects in the resonant vibration response of the biological shield wall inside the reactor building. A small amount of sliding at the soil–foundation interface of the auxiliary building slightly decreases its response, thus reducing its aforementioned negative effects on the reactor building. When soil nonlinearity is accounted for, the rocking vibration mode of the soil–reactor building system almost vanishes, due to the local nonlinear response of the underlying soil. This leads to a beneficial out-of-phase horizontal interaction mechanism between the two buildings that reduces the spectral accelerations at critical points inside the reactor building by up to 55 % for frequencies close to the resonant vibration frequency of the auxiliary building. This showcases the key role of SSSI modelling, and essentially implies that the neighboring buildings could offer mutual seismic protection to each other, in a similar way to the recently emerged seismic resonant metamaterials, provided that they are properly tuned during the design phase, accounting for soil and soil–foundation interface nonlinearities.