Document: NUREG-0800
Document ID: c165ebfe-8431-4d56-8bc9-97c2227d45bb
Document Type: srp
Title: SEISMIC SYSTEM ANALYSIS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0706/ML070640311.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.7.2
CFR Part: 
CFR Title: 

Content:
ting structure, the in-structure response spectra are smoothed and broadened in accordance with the provisions of RG 1.122, to account for uncertainty. (3b) When multiple sets of three time histories, derived from actual earthquake records, are used as the input motion to the supporting structure, the multiple sets of in-structure response spectra already account for some of the uncertainty. Therefore, the provisions of RG 1.122, to account for uncertainty, do not strictly apply. The use of multiple sets of time histories to generate in-structure response spectra is reviewed and accepted on a case-by-case basis. Particularly, the basis for procedures used to account for uncertainties (by variation of parameters) are evaluated. The same acceptance criteria apply to the in-structure response spectra as apply to the design ground response spectrum, reviewed in subsection II.l.B of SRP Section 3.7.1. As an example, if the average of the multiple response spectra generated from the multiple design time histories is used to envelop the design ground response spectrum, then the average of the multiple in-structure response spectra generated from the multiple analyses (each of which used one of the multiple design time histories) are used in design. An evaluation of the statistical correlation between the input ground response spectrum and the output in-structure response spectra should also be provided. The methods used for direct generation of in-structure response spectra are reviewed and accepted on a case-by-case basis. 6. Three Components of Earthquake Motion. RG 1.92, describes acceptable methods for combining the responses due to three components of earthquake motion, for both the response spectrum method and the time history method. Use of alternate methods are evaluated on a case-by-case basis for acceptability. When the three components of earthquake motion are applied simultaneously, using a set of three artificial time histories, the statistical independence of