Document: NUREG-0800
Document ID: 33bf90c7-61c7-4135-894a-cfd9f89a8981
Document Type: srp
Title: -
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1319/ML13198A223.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.7.2
CFR Part: 
CFR Title: 

Content:
Revision 4 – September 2013 embedded structures. Any analysis method based on either a direct approach or a substructure approach can be used provided the following conditions are met: A. The structure, foundation, and soil are properly modeled to ensure that the results of analyses properly capture spatial variation of ground motion, three dimensional effects of radiation damping and soil layering, as well as nonlinear effects from site response analyses. The analyses should incorporate the appropriate soil profiles determined in SRP Sections 2.5.1 through 2.5.3, as well as SRP Section 3.7.1. B. For structures with either surface or shallow embedded foundations, the seismic input motions to the SSI analyses can be typically placed at the free ground surface or at the foundation level using the guidance in SRP Section 3.7.1, as supplemented by DC/COL- ISG-017. However, the input motions defined at locations other than the foundation level may not be appropriate for embedded structures. In these situations, the seismic input should only be specified at the foundation level as the FIRS. C. Perform enough parametric studies with the proper variation of parameters (e.g., soil properties) to address the uncertainties (as applicable to the given site) discussed in Subsection I.4 of this SRP section. It is noted that there is enough confidence in the current methods used to perform the SSI analysis to capture the basic phenomenon and provide adequate design information; however, the confidence in the ability to implement these methodologies is uncertain. Therefore, in order to ensure proper implementation, the following considerations should be addressed in performing SSI analysis: A. Perform sensitivity studies to identify important parameters (e.g., potential foundation uplift, separation and sliding of soil from sidewalls, non-symmetry of embedment, location of boundaries) and to assist in judging the adequacy of the final results. These sensitivity studies can be