Document: NUREG-0800
Document ID: 1121c8ce-ab70-416c-9784-421014a1b25b
Document Type: srp
Title: SEISMIC DESIGN PARAMETERS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1419/ML14198A460.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.7.1
CFR Part: 
CFR Title: 

Content:
k condition as determined from the site exploration activities, and therefore, are unique to a particular site. Competent material is generally considered to be in-situ material having a minimum shear wave velocity of 1,000 feet/second (fps). If non-competent material is present, any excavation and/or backfilling should not alter the development or location of the GMRS. The development of the FIRS should use 1 Outcrop Elevation - An outcrop assumption implies that the outcrop surface is a free surface on which the stresses (normal and shear) are equal to zero, leading to a complete reflection of the incident wave. However, in reality, there may be layers of soil above the assumed outcrop elevation. In these situations, the GMRS or FIRS is computed at depth in a soil profile that includes the effect of the soil layers above on the properties of soil layers below. 3.7.1-3 Revision 4 – December 2014 the site profiles including the effect of backfill. The remaining soft soil or backfill material should be considered in the SSI or other analyses. Further information on the development of the GMRS and FIRS is provided In Interim Staff Guidance (ISG), DC/COL-ISG-01, “Seismic Issues Associated With High Frequency Ground Motion in Design Certification and Combined License Applications,” and DC/COL-ISG-17, “Ensuring Hazard-Consistent Seismic Input for Site Response and Soil Structure Interaction Analyses.” In addition to the FIRS, free-field performance-based surface response spectra (PBSRS) should be developed using the soil column corresponding to the building for which the performance-based FIRS are also generated. The properties of the soil column are used to generate 60 or more randomized sets of properties similar to those used in the probabilistic seismic hazard analysis (PSHA) process as described in SRP Section 2.5.2. The resulting spectra described above are the PBSRS for the horizontal direction. The PBSRS for the vertical direction can be obtained with