Document: NUREG-0800
Document ID: 94da2f11-6df6-47d0-a25e-edeb21a4d649
Document Type: srp
Title: 3.7.1-12
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1419/ML14198A460.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.0
CFR Part: 
CFR Title: 

Content:
in (b) above from falling below the target response spectrum. (d) The computed 5 percent damped response spectrum of the acceleration time history should not exceed the target response spectrum at any frequency by more than 30 percent (a factor of 1.3) in the frequency range of interest. In addition, the power 3.7.1-14 Revision 4 – December 2014 spectrum density of the accelerogram should be computed and shown to not have significant gaps in energy at any frequency over this frequency range. If the design ground motion time history, defined in Approach 2 above, is intended to be compatible to a site-specific FIRS, it should have characteristics consistent with characteristic values for the magnitude and distance of the appropriate controlling events defined for the corresponding uniform hazard response spectrum (UHRS). Option 2: Multiple Sets of Time Histories. As discussed in Section I.1.B and Section II.1.B of this SRP section, the use of multiple real or artificial time histories for analyses and design of SSCs is acceptable. For linear structural analyses, a minimum of four times histories should be used (NUREG/CR-5347). For nonlinear structural analyses, the number of time histories should be greater than four and the technical basis for the appropriate number of time histories are reviewed on a case-by-case basis. This review also includes the adequacy of the characteristics of the multiple time histories. The response spectra calculated for each individual time history may 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. An acceptable method to demonstrate the adequacy of a set of multiple time histories, in terms of enveloping criteria and having sufficient power over the frequency range of interest, is to follow the procedures described for Approach 2 presented in Subsection II.1.B.ii of this SRP.