Document: NUREG-0800
Document ID: 228b9b6e-c81e-4d76-9b8e-12f6c3bd7fa1
Document Type: srp
Title: and Regulatory Guide 1.92,(Reference 10) "Combining Modal Responses
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070336.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.7.2
CFR Part: 
CFR Title: 

Content:
ponents, equipment, and their supports in lieu of the use of a vertical seismic system dynamic analysis is acceptable only if it can be justified that the structure is rigid in the vertical direction. The criterion for rigidity is that the lowest frequency in the vertical direction is more than 33 hz. i. Torsional Effects of Eccentric Masses For seismic Category I systems, if the torsional effect of an eccentric mass such as a valve operator in a piping system is judged to be significant, the eccentric mass and its eccentricity should be included in the mathematical model . The 38 criteria for significance will have to be determined on a case-by-case basis. 3.9.2-13 DRAFT Rev. 3 - April 1996 j. Category I Buried Piping Systems For Category I buried piping systems, the following items should be considered in the analysis: (1) The inertial effects due to an earthquake upon buried piping systems should be adequately accounted for in the analysis. Use of the procedures described in References 11 and 1412 and 15 is acceptable. 39 (2) The effects of static resistance of the surrounding soil on piping deformations or displacements, differential movements of piping anchors, bent geometry and curvature changes, etc., should be adequately considered. Use of the procedures described in Reference 1516 is 40 acceptable. (3) When applicable, the effects due to local soil settlements, soil arching, etc., should also be considered in the analysis. k. Interaction of Other Piping with Category I Piping To be acceptable, each non-Category I piping system should be designed to be isolated from any Category I piping system by either a constraint or barrier, or should be remotely located with regard to the seismic Category I piping system. If it is not feasible or practical to isolate the Category I piping system, adjacent non-Category I piping should be analyzed according to the same seismic criteria as applicable to the Category I piping system. For non-Category I piping systems