Document: NUREG-0800
Document ID: 129133a3-2833-4da5-a564-052efbadbeb2
Document Type: srp
Title: but as applied to Category I subsystems.
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070319.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.7.2
CFR Part: 
CFR Title: 

Content:
le overestimation of seismic responses. Acceptable analysis methods that provide more realistic estimation of seismic responses are discussed in Section 2 of NUREG-1061 (Reference 4).16 In the case of multiple supports located in a single structure, an alternative acceptable method using the floor response spectra involves determination of dynamic responses due to the worst single floor response spectrum selected from a set of floor response spectra obtained at various floors and applied identically to all the floors, provided there is no significant shift in frequencies of the spectra peaks. In addition, the support displacements should be imposed on the supported item in the most unfavorable combination using static analysis procedures. In lieu of the response spectrum approach, time histories of support motions may be used as excitations to the subsystems. Because of the increased analytical effort compared to the response spectrum techniques, usually only a major equipment system would warrant a time history approach. The time history approach does, however, provide more realistic results in some cases as compared to the response spectrum envelope method for multiply-supported systems. 10. Use of Equivalent Vertical Static Factors The acceptance criteria provided in SRP Section 3.7.2, subsection II.10, are applicable. 11. Torsional Effects of Eccentric Masses For seismic Category I subsystems, when the torsional effect of an eccentric mass is judged to be significant, the eccentric mass and its eccentricity should be included in the mathematical model. The criteria for judging the significance will be reviewed on a case-by-case basis. 12. Category I Buried Piping, Conduits, and Tunnels For Category I buried piping, conduits, tunnels, and auxiliary systems, the following items should be considered in the analysis: a. Two types of groundshaking-induced loadings must be considered for design. (i) Relative deformations imposed by seismic waves traveling through the