Document: NUREG-0800
Document ID: e8ae4ac1-29ed-46b1-b4c2-19c7f632e815
Document Type: srp
Title: DYNAMIC TESTING AND ANALYSIS OF SYSTEMS, COMPONENTS, AND
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070336.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.9.2
CFR Part: 
CFR Title: 

Content:
ts and equipment should preferably be selected to be less than 1/2 or more than twice the dominant frequencies of the support structure. Use of equipment frequencies within this range is acceptable if the equipment is adequately designed for the applicable loads. d. Three Components of Earthquake Motion Depending upon what basic methods are used in the seismic analysis, i.e., response spectra or time history method, the following two approaches are considered acceptable for the combination of three-dimensional earthquake effects. (Refs. 11, 12, and 1312, 13, and 14 ) 29 (1) Response Spectra Method When the response spectra method is adopted for seismic analysis, the maximum structural responses due to each of the three components of earthquake motion should be combined by taking the square root of the sum of the squares of the maximum codirectional responses caused by R [ N k 1 Rk 2 ] 1 2 DRAFT Rev. 3 - April 1996 3.9.2-10 (1) EQUATION DELETED each of the three components of earthquake motion at a particular point of the structure or of the mathematical model. (2) Time History Analysis Method When the time history analysis method is employed for seismic analysis, two types of analysis are generally performed depending on the complexity of the problem. (a) to obtain maximum responses due to each of the three components of the earthquake motion: in this case the method for combining the three-dimensional effects is identical to that described in (a) except that the maximum responses are calculated using the time history method instead of the spectrum method. (b) To obtain time history responses from each of the three components of the earthquake motion and combine them at each time step algebraically: the maximum response in this case can be obtained from the combined time solution. When this method is used, to be acceptable, the earthquake motions specified in the three different directions should be statistically independent. e. Combination of Modal Responses When