Document: NUREG-0800
Document ID: 6b7eddf4-f7ce-4821-9f11-e37070221e57
Document Type: srp
Title: DYNAMIC TESTING AND ANALYSIS OF SYSTEMS, STRUCTURES, AND
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1613/ML16133A418.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.9.2
CFR Part: 
CFR Title: 

Content:
systems and components are designed, and the criteria and the applicant’s procedures to establish these parameters are reviewed by the staff in accordance with the guidance of SRP Section 3.7.3. C. Basis for Selection of Frequencies. To avoid resonance, the fundamental frequencies of components and equipment selected should be less than 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 acceptable for the combination of three-dimensional earthquake effects: (i) Response Spectra Method. When the response spectra method is applied 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 co- directional responses caused by each of the three components of earthquake motion at a particular point of the structure or the mathematical model. (ii) Time History Analysis Method. When the time history analysis method is applied for seismic analysis, two methods for combining the responses are acceptable as follows: (1) The method for combining the three-dimensional effects is identical to that described in Item (i) except that the maximum responses are calculated by the time history method instead of the response spectrum method, or (2) 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 is obtained from the combined time solution. When this method is used, the earthquake motions specified in the three different directions should be statistically independent. E. Combination of Modal Responses. SRP