Document: NUREG-0800
Document ID: 671effeb-08bf-46ab-b6de-dd19a026ebb6
Document Type: srp
Title: -
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1235/ML12353A354.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.7.2
CFR Part: 
CFR Title: 

Content:
nd mode shapes may be spurious in the SM solution, which can lead to unconservative or erroneous results. They can be identified as spikes in the transfer functions computed using the SM, which do not appear in the corresponding transfer functions computed using the DM. (2) The limitations of the SM can be mitigated by constraining sufficient interior nodes (as interaction nodes) of the excavated soil volume. This approach is known as the modified subtraction method (MSM). The effect of these additional constraints is to shift the frequencies of the spurious vibration modes above the frequency range of interest to the SSI analysis. (3) A converging trend in the MSM solution may be established by carefully examining the computed transfer functions. The additional interaction nodes should shift the frequencies of the