Document: NUREG-0800
Document ID: e7548e72-8c59-4c82-98dd-ff425e1de29a
Document Type: srp
Title: SEISMIC DESIGN PARAMETERS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1235/ML12352A305.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.7.1
CFR Part: 
CFR Title: 

Content:
rthogonal directions - two horizontal and one vertical. Current practice is to assume that the design response spectra (including maximum ground accelerations) in the two horizontal directions are the same. B. Design Time Histories. The SSE and OBE design ground motion time histories can be either real time histories or artificial time histories. To be acceptable, the design ground motion time histories should consist of three mutually orthogonal directions - two horizontal and one vertical. For both horizontal and vertical input motions, either a single time history or multiple time histories can be used. When time histories are used, each of the three ground motion time histories must be shown to be statistically independent from the others. Each pair of time histories are considered to be statistically independent if the absolute value of their correlation coefficient does not exceed 0.16. Simply shifting the starting time of a given time history cannot be used to establish a different time history. When the seed time histories are selected from real earthquake records, the response spectra corresponding to the seed record should be similar in shape to the target spectra across the frequency range of interest to the analysis (e.g., Houston, et al., 2010) and phasing characteristics of the real earthquake records should be preserved. If the target spectra include multiple characteristic events, a single recorded earthquake time history may not able to capture the response characteristics of the target spectra. To this end, the use of multiple time histories may be appropriate in which individual time histories are developed from real earthquake records fairly representing the characteristic events embodied in the target spectra. Alternatively, an artificial time history may be developed using random generation routines or through the use of multiple time 3.7.1-10 Draft Revision 4 - December 2012 history techniques. If a random time history generator technique is