This paper presents a case study of the soil-structure interaction (SSI) effects on the seismic response of reactor containment and reactor building (RB Complex) structures at a rock site in the Eastern US with input ground motion that is characterized with high frequency content and high peak ground acceleration (PGA). The study includes the effects of 40 ft thick embedment backfill soil on the SSI response and the effects of seismic motion incoherency on the structural response at high frequencies. The responses obtained from these site-specific SSI analyses are compared with results of a set of site-independent SSI analyses that envelope the response of the R/B Complex structures at a wide range of sites characterized with seismic ground motion with frequency content similar to the US NRC RG 1.60 and PGA of 0.3 g. The focus of the study is on the responses obtained from the SSI analyses that serve as basis for defining the demands for seismic design of the building structural members and in-structure response spectra (ISRS) used for seismic design of subsystems, components and equipment. The results of this case study indicate that the seismic design of R/B Complex structures based on SSI responses with a design ground motion which content is reach in the frequencies corresponding to the natural frequencies of vibration of the R/B Complex structures, covers with a significant safety margin the site-specific seismic demands for the hard rock site with high frequency ground motion. Due to the high-frequency seismic input for the site-specific SSI analyses, the site-specific ISRS can be significantly larger in the high-frequency range than the ISRS used for generic design that can affect the operation of high frequency sensitive equipment.
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