Document: NUREG-0800
Document ID: d74a6696-a613-445d-bde8-c50caadd4e4a
Document Type: srp
Title: -
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1235/ML12353A357.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.7.3
CFR Part: 
CFR Title: 

Content:
Draft Revision 4 - December 2012 portion of the fluid contents that moves in unison with the shell. In addition, the fundamental sloshing (convective) mode of the fluid must be included in the horizontal analysis. B. The fundamental natural horizontal impulsive mode of vibration of the fluid-tank system must be estimated giving due consideration to the flexibility of the supporting medium and to any uplifting tendencies for the tank. It is unacceptable to assume a rigid tank unless the assumption can be justified. The horizontal impulsive-mode spectral acceleration, Sa1, is then determined using this frequency and the appropriate damping for the fluid-tank system. Alternatively, the maximum spectral acceleration corresponding to the relevant damping may be used. C. Damping values used to determine the spectral acceleration in the impulsive mode shall be based upon the system damping associated with the tank shell material as well as with the SSI, as specified in NUREG/CR-1161 and Veletsos and Tang (1989.) D. In determining the spectral acceleration in the horizontal convective mode, Sa2, the fluid damping ratio shall be 0.5 percent of critical damping unless a higher value can be substantiated by experimental results. E. The maximum overturning moment, Mo, at the base of the tank should be obtained by the modal and spatial combination methods discussed in Subsection II of SRP Section 3.7.2. The uplift tension resulting from Mo must be resisted either by tying the tank to the foundation with anchor bolts, etc., or by mobilizing enough fluid weight on a thickened base skirt plate. The latter method of resisting Mo must be shown to be conservative. F. The seismically induced hydrodynamic pressures on the tank shell at any level can be determined by the modal and spatial combination methods in SRP Section 3.7.2. The maximum hoop forces in the tank wall must be evaluated with due regard for the contribution of the vertical component of ground shaking. The effects of SSI