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:
structures, if any, on structural response are reviewed. To perform a seismic analysis for an SSI system, it may be necessary to have well- defined excitation or forcing functions applied at the model boundaries to simulate the design earthquake ground motion. It is therefore required in such cases to generate an excitation system acting at the boundaries such that the response motion of the soil media at the plant site in the free field is identical to the design earthquake ground motion. The procedures and theories for regeneration of such an excitation system are reviewed. Any other modeling methods used for SSI analysis are also reviewed, as is any basis for not using an SSI analysis. 5. Development of In-Structure Response Spectra. The procedures and methods for developing in-structure response spectra (e.g., floor response spectra) are reviewed. There are several methods for generating in-structure response spectra. One method makes use of time history analysis by considering single or multiple (real or artificial) ground motion time histories which have response spectra that satisfy the enveloping criteria for the design ground response spectra and the target power spectral density (PSD) function. A second method, which does not require time history analysis, is generally referred to as direct generation of in-structure response spectra. The basis and justification for the use of either of the above methods are reviewed. 6. Three Components of Earthquake Motion. The staff reviews the procedures by which the three components of earthquake motion (time history or response spectra) are considered in determining the seismic response of all seismic Category I SSCs. If three artificial ground motion time histories (two horizontal and one vertical) are applied in a single time history analysis, the statistical independence among the three components is also reviewed. 7. Combination of Modal Responses. When a modal time history analysis method or a response spectrum