Document: NUREG-0800
Document ID: a3c4cb91-c557-4043-bb50-8da01264de08
Document Type: srp
Title: Each calculated spectrum of the artificial time history is considered
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052340564.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.0
CFR Part: 
CFR Title: 

Content:
e design response spectra are considered to be the mean plus one standard deviation (or 84th percentile) response spectra as defined in Section 2.5.2. The review of the real time histories used in the nonlinear analysis is conducted on a case-by-case basis. Some of the specific items of interest are number of time histories, frequency content, amplitude, energy content, duration, number of strong-motion cycles, and the basis for selection of time histories. Additional information on the use of multiple time histories can be found in Reference 8. This information may be used for reference only, as it does not constitute the staff's acceptance criteria. 2. Percentage of Critical Damping Values The specific percentage of critical damping values used in the analyses of Category I structures, systems, and components are considered to be accept- able if they are in accordance with Regulatory Guide 1.61 (Ref. 3). Higher damping values may be used in a dynamic seismic analysis if test data are provided to support them. These values will be reviewed and accepted by the staff on a case-by-case basis. 3.7.1-7 Rev. 2 - August 1989 In addition, a demonstration of the correlation between stress levels and damping values will be required and reviewed for compliance with regulatory position C.3 of Regulatory Guide 1.61. Methods for correlation of damping values with stress level are discussed in References 8 and 9. If such methods are used, they will be reviewed and accepted on a case-by-case basis. The damping values for foundation soils must be based upon measured values or other pertinent laboratory data, considering variation in soil properties and strains within the soil, and must include an evaluation of dissipation from pore pressure effects as well as material damping for saturated site conditions. 3. Supporting Media for Category I Structures To be acceptable, the description of supporting media for each Category I structure must include foundation embedment depth, depth