Document: NUREG-0800
Document ID: f58a3e4a-be8a-4b75-8b11-b41b7a54a500
Document Type: srp
Title: SEISMIC DESIGN PARAMETERS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052340564.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.7.1
CFR Part: 
CFR Title: 

Content:
ke (SSE) (Ref. 2) are reviewed against the free-field response spectra that are reviewed and accepted under SRP Section 2.5.2. The distinction between the free-field response spectra (site specific or otherwise) reviewed in Section 2.5.2 and the design response spectra reviewed in this section is that a design response spectrum, in general, is a relatively smooth plot not exhibiting random peaks and valleys while a free-field response spectrum may exhibit random sharp peaks and valleys. The use of smooth spectra is preferred in the design and in certain situations it is needed (for example, in the design of a standard plant). The use.of unsmoothed response spectra will be reviewed on a case-by- case basis. b. Design Time History For computing the response of Category I structures and equipments, acceleration time histories may be used. These time histories must be compatible with the design response spectra, site specific or otherwise, as described above. When an appropriate recorded or specified time history is not avail- able as input motion for seismic system analysis, an artificial time history (three components) may be generated from the design response spectra for the purpose of carrying out a time history analysis. The response spectra obtained from such an artificial time history of motion should generally envelop the design response spectra for all damping values to be used. The procedures used to generate response spectra are reviewed. In addition to the comparison of the response spectra derived from the time history with the design response spectra, the frequency intervals at which the spectral values are calculated are also reviewed. When time history analyses are performed, either of the following options may be considered. In either case the time histories may be real or artificial. 3.7.1-2 Rev. 2 - August 1989 Option 1: Single Time History Use of single time history is justified by satisfying a target power spectral density (PSD) requirement in