Document: NUREG-0800
Document ID: 47e82a83-5ed9-4532-9612-496bc297f1d4
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 6. Enhanced SRP Section 3.7.2 II.4 “Soil-Structure Interaction” by adding acceptance criteria related to SSI analysis of embedded structures using the substructure approach (direct vs. subtraction methods). The technical rationale for this change is as follows. For the case of embedded structures, two analytic methods have been used in SSI computations based on the substructure approach. The first method, referred to as the flexible volume or DM, is the most reliable but also the most computationally intensive method. The DM incorporates all nodes of the finite element mesh for the excavated below-grade zone of the embedded structure (termed the interaction nodes) in the solution. The second method, known as the SM, uses an approximate simplification that yields significant reductions in computational effort. It reduces the number of the interaction nodes to only those on the boundary of the excavated zone and assumes that the remaining interior nodes do not need to be connected to the boundary nodes. However, recent SSI analyses performed for certain U.S. Department of Energy facilities identified limitations associated with the SM. It was found that, if not implemented properly, the application of the SM to the SSI analysis of embedded structures may result in erroneous and unconservative SSI responses when compared to the DM. To identify limitations and mitigate potential errors associated with the SM, and to ensure that a conservative seismic analysis is performed, SRP Section 3.7.2 guidance regarding SSI analysis was enhanced to provide additional criteria for reviewing SSI analysis of embedded structures performed using the SM. 7. Enhanced SRP Section 3.7.2 II.4 “Soil-Structure Interaction” by adding acceptance criteria related to SSI analysis incorporating the effects of ground motion incoherency. The technical rationale for this change is as follows. Advanced analytical methods are being applied in the nuclear industry,