Seismic Response of NPP Considering the Non-Linear Soil-Structure Interaction Effects Using DRM

Abstract For improvement of seismic capacity of NPP, the Non-linear SSI (NLSSI) analysis concepts are studied and applied to practical NPP (Nuclear Power Plant) Structural Analysis. Nonlinear SSI analysis requires a different approach from existing linear and frequency domain SSI analysis. In order to consider the non-linear behavior of the ground and structural materials, the analysis must be performed in the time domain, but this is difficult due to a large analysis model and many repetitive analyzes. Accordingly, many researches are being actively conducted to introduce a hybrid method that sets a certain region as the near field, adds boundary elements, and conducts analysis in the frequency domain or time domain. DRM (Domain Reduction Method) is a method proposed by Bielak et al. by developing several theories for calculating effective seismic force, and is the most widely used technique when analyzing NLSSI using the sub-structure method. This method is also provided in LS-DYNA. In this study, the Korean NPP Structures are analyzed with ABAQUS program in the time domain for the NLSSI analysis. The Linear SSI analysis of the NPP Structure is performed with ACS SASSI program in the frequency domain at same time, and LSSI analysis result is compared to NLSSI analysis result. The final produce of NLSSI analysis is the FRS (Floor Response Spectrum) at each story of building. After NLSSI analysis, FRS will be provided for re-calculation of the HCLPF (High Confidence of Low Probability of Failure) of some critical equipment that contribute significantly to the CDF (Core Damage Frequency).