Document: NUREG-0800
Document ID: 7c104096-d040-463a-a94b-a0af08ab3478
Document Type: srp
Title: DYNAMIC TESTING AND ANALYSIS OF SYSTEMS, STRUCTURES, AND
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0702/ML070230008.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.9.2
CFR Part: 
CFR Title: 

Content:
sed in subsection II.9 of SRP Section 3.7.3. In lieu of the response spectrum approach, time histories of support motions may be used as excitations to the systems. Because of the increased analytical effort compared to the response spectrum techniques, usually only a major equipment 3.9.2-14 Revision 3 - March 2007 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. H. Use of Constant Vertical Static Factors. The use of constant vertical load factors as vertical response loads for the seismic design of all Category I systems, components, equipment, and their supports in lieu of a vertical seismic system dynamic analysis is acceptable only if the structure is demonstrably rigid in the vertical direction. The criterion for rigidity is that the lowest frequency in the vertical direction be more than 33 Hz. I. Torsional Effects of Eccentric Masses. For Seismic Category I systems, if the torsional effect of an eccentric mass like 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 criteria for significance will have to be determined case by case. J. Category I Buried Piping Systems. For Category I buried piping systems, the following items should be considered in the analysis: (i) The inertial effects due to an earthquake upon buried piping systems should be adequately considered in the analysis. Use of the procedures described in the references is acceptable. (ii) 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 the references is acceptable. (iii) When applicable, the effects of local soil settlements, soil