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:
ubmitted on or after January 10, 1997. Applications subject to this appendix must: $ Demonstrate that the SSE ground motion in the horizontal direction in the free-field at the foundation level of the structures must be an appropriate response spectrum with a peak ground acceleration of at least 0.1g. $ Design SSCs to the OBE and SSE loadings. However, if the OBE is set at one-third or less of the SSE, an explicit analysis or design is not required. If the OBE is set at a 3.7.1-3 Draft Revision 4 - December 2012 value greater than one-third of the SSE, an analysis and design must be performed for the OBE to demonstrate that the applicable stress, strain, and deformation limits of the SSCs are satisfied. The magnitude of the OBE in the application is reviewed to determine whether a seismic analysis is required for this earthquake level. Throughout this SRP section, whenever the OBE is discussed, it is understood that it may not apply to the particular licensing application being reviewed depending on the magnitude of the OBE as defined above. A. Design Response Spectra. Design response spectra are used in the design of seismic Category I SSCs, and they are generally specified at the top of the ground surface in the free-field or at the top of the first layer of competent material as outcrop motion if soil layers near the surface will be completely excavated to the competent material. The proposed design response spectra for the OBE and SSE are reviewed against the free-field site-specific GMRS that are reviewed and accepted under SRP Section 2.5.2. The design response spectra, in general, are relatively smooth plots not exhibiting random peaks and valleys. The use of smooth spectra is preferred in the design and is needed for generic site seismic hazard evaluation, as in the design of a standard plant. The use of unsmoothed design response spectra to develop the input ground motion (design time history) will be reviewed on a case-by-case basis. A review is also made