Document: NUREG-0800
Document ID: e7548e72-8c59-4c82-98dd-ff425e1de29a
Document Type: srp
Title: SEISMIC DESIGN PARAMETERS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1235/ML12352A305.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.7.1
CFR Part: 
CFR Title: 

Content:
d, either of the following options 3.7.1-4 Draft Revision 4 - December 2012 may be considered. In either case, the time histories may be real or artificial. Option 1: Single Set of Time Histories. The justification for the use of the single set of time histories is reviewed. The approach used to demonstrate that the response spectra generated from the time histories envelop the design response spectra are reviewed. Depending on the approach used, the application of the requirements to match a target power spectral density (PSD) function compatible with the design response spectra may also need to be reviewed. Option 2: Multiple Sets of Time Histories. In lieu of the use of a single time history, multiple artificial or real ground motion time histories may be used for the seismic analyses and design of the SSCs. The parameters describing the time histories and the number of time histories are reviewed. The approach used to demonstrate the adequacy of the set of multiple time histories, in terms of the enveloping requirements and having sufficient power over the frequency range of interest, is reviewed. In some instances, a nonlinear analysis of the SSCs may be appropriate (e.g., the evaluation of existing structures). Multiple time history analyses incorporating real earthquake time histories are appropriate when such analyses are proposed. The adequacy of time histories used for the nonlinear analyses is reviewed. 2. Percentage of Critical Damping Values. The percentage of critical damping values used for the seismic analysis of Category I SSCs is reviewed for both the OBE and the SSE. Critical damping is the amount of damping that would completely eliminate free vibration and is an important measure of the damping capacity of a structure. Vibrating SSCs have energy losses that depend on numerous factors, such as material characteristics, stress levels, and geometric configuration. This dissipation of energy, or damping effect, occurs because a part of the