Document: NUREG-0800
Document ID: e40387bd-a6d6-49ae-a11b-6d22124df03a
Document Type: srp
Title: Each calculated spectrum of the artificial time history is considered to envelop the
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070317.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.0
CFR Part: 
CFR Title: 

Content:
tra generated from these time histories envelop the design response spectra. The 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. DRAFT Rev. 3 - April 1996 3.7.1-8 Additional information on the use of multiple time histories can be found in NUREG/CR-1161 (Reference 88) . This information may be used for reference 40 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 SSCs are considered to be acceptable if they are in 41 accordance with Regulatory Guide 1.61 (Ref. 3) . Alternatively, damping values 42 derived from Appendix N to ASME Code Section III, Division 1, Code Case N-411-1, insofar as they are compatible with the guidance provided in Regulatory Guide 1.84, are acceptable. Higher damping values may be used in a dynamic seismic analysis if test 43 data are provided to support them. These values will be reviewed and accepted by the staff on a case-by-case basis. 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 NUREG/CR-1161References 8 and 9in ASCE Std 4-86 (Reference 11) . If such 44 45 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,