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:
al 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 target PSD as defined by Equation (2) from 0.3 Hz to 24 Hz. Less than 2.5 Hz ( ) S f o = 0.419 m 2/sec 3 ( f / 2.5 Hz) 0.2 2.5 Hz to 9.0 Hz ( ) S f o = 0.419 m 2/sec 3 (2.5 Hz / f ) 1.8 ........................................................................(2) 9.0 Hz to 16.0 Hz ( ) S f o = 418 cm 2/sec 3 (9.0 Hz / f ) 3 Greater than 16 Hz ( ) S f o = 74.2 cm 2/sec 3 (16.0 Hz / f ) 8 ( ) ( ) S f F f T o D = 2 2 2 π 3.7.1-25 Draft Revision 4 - December 2012 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 24 Hz for the target PSD is so low as to be inconsequential so that checks above 24 Hz are unnecessary. (However, note that the response spectrum calculations are required beyond 24 Hz as governed by RG 1.60 definitions.) 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 RG 1.60 response spectrum. A time history meeting this minimum PSD requirement will produce a response spectrum that lies below the RG 1.60 response spectrum at all frequencies. To produce a response spectrum that accurately fits the 2 percent damped, 1.0 g, RG 1.60 response spectrum at all frequencies above 0.25 Hz, the PSD defined by Equation (2) can be used with the resulting time history being clipped at ±1.0 g (see NUREG/CR-3509). To produce a response spectrum that conservatively envelops the 1.0 g, RG 1.60 response spectrum at 2 percent damping and