Influence of Embedment Depth on Floor Response Spectrum of SMR Structure Incorporating Dynamic Soil–structure Interaction

Small Modular Reactors (SMRs) offer significant advantages over traditional large-scale Nuclear Power Plants (NPPs) in terms of simplicity, scalability, cost-effectiveness, and safety. However, ensuring the seismic safety of SMRs is of paramount concern, as they must endure the effects of earthquakes without compromising their safety and functionality. SMR structures are often partially or completely submerged below the surface, making their seismic responses influenced not only by their inherent characteristics but also by their interaction with the surrounding soil, a phenomenon known as soil–structure interaction (SSI), and embedment depth. Although previous studies have performed seismic SSI analyses of general structures, SMR structures have unique characteristics that affect their SSI effects, making their responses different from those of general structures. In addition to these considerations, the Floor Response Spectrum (FRS) holds critical importance as a structural response parameter for a NPP. Consequently, this study investigates how embedment depth influences the FRS of SMR structures under seismic SSI effects. The analysis considers three soil sites with different geological properties to capture the variability of SSI effects. The investigation results show how FRS changes with different embedment depths under seismic excitation. SSI effects can either reduce or increase FRS, largely depending on the frequency contents of foundation input motions and site conditions. Embedment depth generally reduces amplitudes of FRS, but it can also cause FRS peak shifting that increases amplitudes of FRS at some frequencies. Based on the investigation, the study recommends careful analysis of site conditions and embedment depth for optimal seismic design of SMR structures.