Document: NUREG-0800
Document ID: 73747cf4-ff95-449b-b6b0-53dc0755b9e0
Document Type: srp
Title: OTHER SEISMIC CATEGORY I STRUCTURES
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1235/ML12353A382.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.8.4
CFR Part: 
CFR Title: 

Content:
3.8.4 “Other Seismic Category I Structures” Description of Changes This SRP section affirms the technical accuracy and adequacy of the guidance previously provided in Revision 3, dated May 2010 of this SRP. See ADAMS Accession No.ML100630323. I. AREAS OF REVIEW 1. Enhanced SRP Section 3.8.4 I.3 “Loads and Load Combinations” item A, to include loads induced by the construction sequence and differential settlements. See item 2 in SRP Section 3.8.5, “Description of Changes, II Acceptance Criteria,” for the technical rationale for this change. II. ACCEPTANCE CRITERIA 1. Revised SRP Section 3.8.4 II.4 “Design and Analysis Procedures” item H, to include enhanced guidance to compute dynamic soil pressures on embedded walls. The technical rationale for this change is as follows. The computation of seismically induced lateral soil pressures on embedded walls is acknowledged to be complex and dependent on many factors. Under static at-rest conditions, the soil pressures are primarily controlled by soil type, soil compaction (or relative density), and groundwater conditions. For granular materials, typically placed as backfill in the immediate vicinity of the wall, the static at-rest pressures at a given depth are estimated by Ko x σv, where σv is the vertical intergranular stress due to the weight of the soil above the depth of interest and Ko is called the at-rest coefficient of earth pressure. The parameter Ko is typically estimated to be approximately 0.5. Under seismic conditions, the pressures change from the static case and are primarily controlled by the relative motion developed between the wall or structure and the free- field. If the wall or structure moves away from the soil, these dynamically induced pressures decrease from the static at-rest pressures. This stress state is termed the active state. The minimum value of this active state is estimated for ordinary conditions as Ka x σv, where Ka is called the Rankine active coefficient of earth