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:
for a compatible target PSO are contained in Appendix A. Target PSD functions other than those given in Appendix A can be used if justified. For site-specific design response spectra or spectra other than Regulatory Guide 1.60 spectra, a compatible target PSD should be generated. For generation of target PSD in such cases, procedures outlined in Reference 6 can be used. For cases where a time history ensemble is used for generation of site-specific spectra, the same time histories can be used to generate mean plus one standard deviation (or 84th percentile) PSD function as a target PSD function. Procedures used to generate the target PSD will be reviewed on a case-by-case basis. The PSD requirements are included as secondary and minimum requirements to prevent potential deficiency of power over the frequency range of interest. It should be noted that the ground motion is still primarily defined by the design response spectrum. The use of PSD criteria itself can yield time histories that may not envelop the design response spectrum. Option 2: Multiple Time Histories As discussed in Section I.1.b of this SRP, the use of multiple real or artificial time histories for analyses and design of structures, systems, and components is acceptable. As a minimum, four time histories should be used for analyses. Any lesser number will be reviewed and accepted on a case-by-case basis. The parameters describing the time histories and the calculated response spectra for each time history are reviewed. The response spectra calculated for each individual time history need not envelop the design response spectra. However, the multiple time histories are acceptable if the average calculated response spectra 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