Document: NUREG-0800
Document ID: 29f5ac9f-4962-4021-913a-6375076e03fd
Document Type: srp
Title: SEISMIC SYSTEM ANALYSIS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052340566.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.7.2
CFR Part: 
CFR Title: 

Content:
tion for surface or embedded structures. Any analysis method based on either a direct approach or a substructure approach can be used provided the following conditions are met: 3.7.2-8 Rev. 2 - August 1989 I: a. The structure, foundation, and soil are properly modeled to ensure that the results of analyses are within the range of applicability of the particular method employed. b. The input motion at the base of a discrete soil model or soil column should produce the specified design spectra at the free surface of the soil profile in the free field (finished grade). 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 (Ref. 4): a. Perform sensitivity studies to identify important parameters (e.g., bonding and debonding of side walls, nonsymmetry of embedment, location of boundaries) and to assist in judging the adequacy of the final results. These sensitivity studies can be performed by the use of well-founded and properly substantiated simple models to give better insight; b. Through the use of some appropriate benchmark problems, the user should demonstrate its capability to properly implement any SSI methodologies; and c. Perform enough parametric studies with the proper variation of para- meters (e.g., soil properties) to address the uncertainties (as applicable to the given site) discussed in subsection 1.4 of this SRP section. For sites where SSI effects are considered insignificant and fixed base analyses of structures are performed, bases and justification for not performing SSI analyses are reviewed on a case-by-case basis. If the SSI analysis is not required, the input motion at the base of the structures will be the design