Document: NUREG-0800
Document ID: 45f5d841-54ef-4876-be3e-86eafc6ca90a
Document Type: srp
Title: Each calculated spectrum of the artificial time history is considered to envelop
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1235/ML12352A305.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.0
CFR Part: 
CFR Title: 

Content:
ide a Nyquist frequency (Nf =1/(2Δt), where Δt = time increment) above the maximum frequency of interest. The total duration of the record can be increased by zero packing to satisfy these frequency criteria. (b) Spectral acceleration at 5 percent damping shall be computed at a minimum of 100 points per frequency decade, uniformly spaced over the log frequency scale from 0.1 Hz to 50 Hz or the Nyquist frequency. The comparison of the response spectrum obtained from the artificial ground motion time history with the target response spectrum shall be made at each frequency computed in the frequency range of interest. (c) The computed 5 percent damped response spectrum of the accelerogram shall not fall more than 10 percent below the target response spectrum at any one frequency. To prevent response spectra in large frequency windows from falling below the target response spectrum, the response spectra within a frequency window of no larger than ±10 percent centered on the frequency shall be allowed to fall below the target response spectrum. This 3.7.1-13 Draft Revision 4 - December 2012 corresponds to response spectra at no more than 9 adjacent frequency points defined in (b) above from falling below the target response spectrum. (d) The computed 5 percent damped response spectrum of the artificial ground motion time history shall 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 spectrum density of the accelerogram needs to be computed and shown to not have significant gaps in energy at any frequency over this frequency range. If the artificial ground motion time history, defined in Approach 2 above, is intended to be compatible to a site-specific GMRS, it shall 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).