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:
..................................(1) where TD is the strong motion duration over which ( ) F f is evaluated. This duration TD represents the duration of near maximum and nearly stationary power of an acceleration time history record. Additional guidance on estimation of TD for artificial time history or actual earthquake time history is provided in Appendix B of NUREG/CR-5347. The average one-sided PSD defined by Equation (1) should exceed 80 percent of the appropriate Magnitude and Distance bin target PSD as shown in Tables 1 through 4. At any frequency f , the average PSD is computed over a frequency band width of ±20 percent, centered on the frequency f (e.g., 4 Hz to 6 Hz band width for f = 5 Hz). The power above 25 Hz for the PSD targets for Western US Sites and Central and Eastern US Soil Sites is so low as to be inconsequential so that checks above 25 Hz are unnecessary. For Central and Eastern US Rock Sites checks above 50 Hz are unnecessary. (However, note that the response spectrum calculations are required beyond 25 Hz and 50 Hz, as appropriate.) Similarly, power below 0.3 Hz has no influence on stiff nuclear plant facilities, so that checks below 0.3 Hz are unnecessary. This minimum check is set at 80 percent of the target PSD so as to be sufficiently high to prevent a deficiency of power over any broad frequency band, but sufficiently low that this requirement introduces no additional conservatism over that already embodied in the specified target response spectrum. ( ) ( ) S f F f T o D = 2 2 2 π 3.7.1-27 Draft Revision 4 - December 2012 A time history meeting this minimum PSD requirement will produce a response spectrum that lies below the target response spectrum at all frequencies. To produce a response spectrum that accurately fits the 2 percent damped, 1.0 g, target response spectrum at all frequencies above 0.25 Hz, the PSD specified in Tables 1 through 4 can be used with the resulting time history being clipped at ±1.0 g (see NUREG/CR-3509).