Document: NUREG-0800
Document ID: 6171d065-38ce-4cde-aa53-058baf32948a
Document Type: srp
Title: 2.82
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1419/ML14198A460.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.16
CFR Part: 
CFR Title: 

Content:
sed to generate the Fourier spectrum using Equation (1). The PSD function was linearly interpolated in the log-log scale to fill all frequency points for the Fourier coefficients. This method produces the same acceleration time histories as the method in Appendix B of NUREG/CR-5347. (2) Apply a trapezoidal envelope function to the synthetic time histories (rise time = 1.4 s, strong motion duration = 10.24 s, and decay time = 7.0 s), which is Function B in Appendix B of NUREG/CR-5347. (3) Calculate the 5 percent damped absolute acceleration response spectra for the synthetic time histories and obtain the arithmetic average RSavg. (4) Multiply the PSD frequency-by-frequency by (RSrep/RSavg)2, and use this adjusted PSD in the next iteration. Convergence on the bin representative RSrep can be quickly achieved in the dominant frequency range of interest to structural response. However, in some cases, at the very low and/or very high frequencies, successive iterations could lead to increase or decrease of the PSD values without noticeable improvement to the RSrep match. This behavior may be due to the inadmissibility of the bin representative RSrep; they were developed by statistically fitting to the bin average RS shapes and may not necessarily be physical at these extreme frequencies. Therefore, in those cases, the PSD values at a few very low frequencies (close to 0.1 Hz) or very high frequencies (close to 100 Hz) were manually adjusted. The tabulated target PSD’s in Tables 1 and 2 are values after the manual adjustment. The converged target PSD’s were smoothed using cubic splines at the frequency points as shown in the first column of Tables 1 and 2, and the tabulated target PSD’s represent the smoothed PSD’s. 3.7.1-33 Revision 4 – December 2014 B.2 Development of Target PSD for Other Response Spectral Shapes For a design response spectrum different from the NUREG/CR-6728 bin representative RSrep, the iterative frequency-by-frequency scaling procedure