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:
to envelop the design response spectrum when no more than five points fall below, and no more than 10 percent below, the design response spectrum. Recent studies indicate that numerically generated artificial ground acceleration histories produce power spectral density (PSD) functions having a quite different appearance from one individual function to another, even when all these time histories are generated so as to closely envelop the same design response spectra. For example, the use of the available techniques of generating acceleration histories that *satisfy enveloping Regulatory Guide 1.60 (Ref. 5) spectra usually results in PSD functions that fluctuate significantly and randomly as a function of frequency. It is also recognized that the more closely one tries to envelop the specified design response spectra, the more significantly and randomly do the spectral density functions tend to fluctuate and these fluctuations may lead to an unconserva- tive estimate of response of some structures, systems, and components. Therefore, when a single artificial time history is used in the design of seismic Category I structures, systems, and/or components, it must in general satisfy requirements for both enveloping design response spectra as well as adequately matching a target PS0 function compatible with the design response spectra (Ref. 7). Therefore, in addition to the response spectra enveloping requirement, the use of a single time history will also be justified by demonstrating sufficient energy at the frequencies of interest through the generation of PSD function, which is greater than a target PSD function throughout the frequency range of significance. . 3. 7.1- 6 Rev. 2 - August 1989 When Regulatory Guide 1.60 spectra are used as design spectra the requirements 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