Document: NUREG-0800
Document ID: b7a0d763-ceb9-4c46-9f32-fe983972eb1a
Document Type: srp
Title: -
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1235/ML12353A354.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.7.2
CFR Part: 
CFR Title: 

Content:
onal 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, to develop seismic responses to high frequency ground motion inputs, incorporating the effect of ground motion incoherency. The phenomenon of ground motion incoherency in the free field has been investigated and characterized in terms of coherency functions, based on recorded earthquake data collected from dense array seismic data. The ground motion incoherency effect on structural response is considered by incorporating a coherency function in analytical methods for SSI analyses. SSI analyses based on analytical methods that consider ground motion incoherency generally reduce structural response in high frequencies, compared to the response based on the traditional assumption of ground motion coherency. However, the effect of incoherent ground motion may cause an increase in motions associated with overturning and torsional structural responses. Although the development of the coherency function incorporated a degree of conservatism which was intended to compensate to a certain extent for the uncertainty associated with the lack of data for the high frequency hard rock sites in the Eastern US and the ground motion variability with depth, it is important to recognize that the reductions in structural response due to ground motion incoherencies are quantified based on analytical models which utilize the coherency function described in DC/COL-