Document: NUREG-0800
Document ID: 94da2f11-6df6-47d0-a25e-edeb21a4d649
Document Type: srp
Title: 3.7.1-12
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1419/ML14198A460.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.0
CFR Part: 
CFR Title: 

Content:
he design should be revised to eliminate this behavior. 2. Percentage of Critical Damping Values. The specific percentage of critical damping values used in the analyses of seismic Category I, SSCs is considered to be acceptable if they are in accordance with RG 1.61. Damping values different from those listed in RG 1.61 (e.g., higher damping values) may be used in a dynamic seismic analysis if test data are provided to support them. These damping values are reviewed and accepted by the staff on a case-by-case basis. In addition, a demonstration of the correlation between stress levels and damping values is required and reviewed to determine if the applicable regulatory position in RG 1.61 is met. If other methods for correlation of damping values with stress level are used, they should be reviewed and accepted on a case-by-case basis. The material soil damping for foundation soils should be based upon validated values or other pertinent laboratory data, considering variation in soil properties and strains within the soil, and should include an evaluation of dissipation from pore pressure effects as well as material damping for saturated site conditions. The maximum soil damping value acceptable to the staff is 15 percent. 3. Supporting Media for Seismic Category I Structures. To be acceptable, the description of supporting media for each seismic Category I structure should include foundation embedment depth, depth of soil over bedrock, soil layering characteristics, design groundwater elevation, dimensions of the structural foundation, total structural height, and soil properties such as shear wave velocity, shear modulus, material damping, including strain-dependent effect, as well as Poisson's ratios, and density as a function of depth. If the minimum shear wave velocity of the supporting foundation material is less than 1,000 fps, additional studies should be performed which consider the average shear wave velocity, and its degree of variability addressing