Document: NUREG-0800
Document ID: 1f106a50-722f-45fa-952a-2e7ab7d836c1
Document Type: srp
Title: DYNAMIC TESTING AND ANALYSIS OF SYSTEMS, COMPONENTS, AND EQUIPMENT
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052360453.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.9.2
CFR Part: 
CFR Title: 

Content:
- July 1981 displacements can be obtained from the structural response cal- culations or, as a conservative approximation, by using the floor response spectra. For the latter option, the maximum dis- placement of each support is predicted by Sd = Safg/W 2, where Sa is the spectral acceleration in "g's" at the high frequency end of the spectrum curve (which, in turn, is equal to the maximum floor acceleration), g is the gravity constant, and w is the fundamental frequency of the primary support structure in radians per second. The support displacements can then be imposed on the supported item in the most unfavorable combination. The responses due to the inertia effect and relative displacements should be combined by the absolute sum method. In the case :of multiple supports located in a single structure, an alternate 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 iden- tically 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 pro- cedures. In lieu of the response spectrum approach, time histories of support motions may be used as excitations to the systems (Ref. 16). 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. 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, com- ponents, equipment, and their supports in lieu