Document: NUREG-0800
Document ID: 78905d69-1945-4638-99b9-2db68eb3da77
Document Type: srp
Title: SEISMIC SYSTEM ANALYSIS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070318.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.7.2
CFR Part: 
CFR Title: 

Content:
tural model and proper representation of DOF masses. An acceptable alternative to this procedure is as follows: Modal responses are computed for enough modes to ensure that the inclusion of additional modes does not increase the total response by more than 10 percent. Modes that have natural frequencies less than that at which the spectral acceleration approximately returns to the ZPA (33 Hz in the case of Regulatory Guide 1.60 response spectra) are combined in accordance with Reference 8Regulatory Guide 1.92. Higher-mode responses are combined algebraically (i.e., 91 retain sign) with each other. The absolute value of the combined higher modes is then added directly to the total response from the combined lower modes. DRAFT Rev. 3 - April 1996 3.7.2-30 [This Page Intentionally Left Blank] SRP Draft Section 3.7.2 Attachment A - Proposed Changes in Order of Occurrence 3.7.2-31 DRAFT Rev. 3 - April 1996 Item numbers in the following table correspond to superscript numbers in the redline/strikeout copy of the draft SRP section. Item Source Description 1. Editorial - Current PRB names and Editorial change made to reflect current PRB name abbreviations. and responsibility for SRP section 3.7.2. 2. Editorial. Consistent with other SRP sections, added the acronym SSC for "structure system and component," to be used in lieu of the full expression. 3. Editorial. Substituted grammatically correct verb form to match subject of clause; the soil deposits are assumed to be symmetrical. 4. Editorial. Substituted the acronym SSC for "structure, system and component." This acronym was introduced at the beginning of this SRP section, as its use is consistent with other SRP sections. 5. Editorial. Substituted the acronym SSC for "structure, system and component." This acronym was introduced at the beginning of this SRP section, as its use is consistent with other SRP sections. 6. Integrated Impact 101. Revised paragraph I.8 of Areas of Review to clarify the applicability of seismic