Document: NUREG-0800
Document ID: c165ebfe-8431-4d56-8bc9-97c2227d45bb
Document Type: srp
Title: SEISMIC SYSTEM ANALYSIS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0706/ML070640311.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.7.2
CFR Part: 
CFR Title: 

Content:
rial is defined as in-situ material having a minimum shear wave velocity of 1,000 feet/second (fps). iii. When the guidance for SSI analysis presented above is not completely implemented, the spectral amplitude of the acceleration response spectra (horizontal component of motion) in the free field at the foundation depth shall be not less than 60 per cent of the corresponding design response spectra at the finished grade in the free field. When variation in soil properties are considered (as required by the “Specific Guidelines for SSI Analysis” below), the 60 percent limitation may be satisfied using an envelope of the three spectra corresponding to the three soil properties. If the accompanying rotational components of the input motion are ignored, no reduction is permitted in the horizontal component at the foundation level. Specific Guidelines for SSI Analysis The following specific guidelines are provided here to facilitate the review and draw the attention of reviewers to some important aspects of the SSI analysis. These guidelines are not necessarily requirements for the acceptance of any methodologies or an SSI analysis. ! The behavior of soil, though recognized to be nonlinear, can often be approximated by linear techniques. Truly nonlinear analysis is not required unless the comparison of results from large-scale tests or actual earthquakes and analytical results indicate deficiencies that cannot be accounted for in any other manner. The nonlinear soil behavior may be accounted for by the following: 3.7.2-12 Revision 3 - March 2007 - Using equivalent linear soil material properties typically determined from an iterative linear analysis of the free-field soil deposit. This accounts for the primary nonlinearity, or - Performing an iterative linear analysis of the coupled soil-structure system. This accounts for the primary and secondary nonlinearities. In the event the nonlinear analysis is chosen, the results of the nonlinear analysis should be judged