Document: NUREG-0800
Document ID: b759cd98-66f9-41cf-b880-4b1e52a3561c
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:
Draft Revision 4 - December 2012 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 analysis method is used to calculate the seismic response of SSCs, the contribution to the total response due to the effects of high frequency modes (i.e., modes with natural frequencies greater than the frequency at which the spectral acceleration converges to approximately the zero period frequency, ZPA) is reviewed, to ensure that the total response closely simulates the behavior of the SSC during a seismic event. For the case of the Regulatory Guide (RG) 1.60 response spectrum, ZPA is about 33 Hz. When a response spectrum method is used, the procedure for combining modal responses, including modes with closely spaced frequencies, is reviewed. 8. Interaction of Non-Category I Structures with Category I SSCs. The design criteria to account for the seismic motion of non-Category I structures (or portions thereof) in the seismic design of Category I structures (or portions thereof) are reviewed. The seismic design of structures whose continued function is not required but whose failure could adversely impact the safety function of a Category I SSC, or result in incapacitating injury to control room occupants, is reviewed. Any special design features employed to protect Category I SSCs from the structural failure of non-Category I