Document: NUREG-0800
Document ID: c3ea80e5-e862-496d-babf-f2404035419d
Document Type: srp
Title: 4.76
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1419/ML14198A460.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.05
CFR Part: 
CFR Title: 

Content:
derprediction at adjacent frequencies. 3. Enhanced guidance in SRP Section 3.7.1 II.1.B ii, Option 1 - single set of time histories, Approach 2) Item (d). The technical rationale for this change is as follows. The first criterion in Item (d) of the SRP ensures there is no significant over-prediction of the response spectrum of the ground motion time history. The second criterion ensures that there will not be a significant energy gap at any frequency over the frequency range of interest. Both criteria should be satisfied to ensure that overestimation of the spectral matching at certain frequencies would not cause significant deficiencies in energy at other frequencies. 4. Enhanced guidance in SRP Section 3.7.1 II.1.B, Option 2 - multiple sets of time histories. The technical rationale for this change is as follows. 3.7.1-44 Revision 4 – December 2014 In view of the complexities of performing nonlinear time history analyses, it is difficult to identify a specific number of time history input motions that should be used. To do so would require additional research that should include performing many nonlinear time history analyses on various structures and components. However, there is some guidance in other standards on selection of the number of earthquake motions and how to select the responses from the multiple nonlinear time history analyses. For seismic analysis and design of buildings, Section 1618 of the 2003 International Building Code (IBC) identifies that dynamic analysis including nonlinear time history analysis shall be performed in accordance with the requirements of the ASCE 7 Standard Section 16.2.4 of ASCE/SEI 7-05 indicates that: “If at least seven ground motions are analyzed, the design values of member forces, QE, member inelastic deformations, Ψ, and story drift, Δ, are permitted to be taken as the average of the QEi, Ψi, and Δi values determined from the analyses. If fewer than seven ground motions are analyzed, the design member forces,