Document: NUREG-0800
Document ID: 10bc45c3-8e70-44ed-a57b-2dd08d4ef847
Document Type: srp
Title: SEISMIC SUBSYSTEM ANALYSIS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0706/ML070640313.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.7.3
CFR Part: 
CFR Title: 

Content:
owever, the commonly used alternative of analyzing such tanks by the "Housner-method" described in TID-7024 may be inadequate in some cases. The major problem is that direct application of this method is consistent with the assumption that the combined fluid-tank system in the horizontal impulsive mode is sufficiently rigid to justify the assumption of a rigid tank. For flat-bottomed tanks mounted directly on their bases, or tanks with very stiff skirt supports, the assumption leads to the usage of a spectral acceleration equal to the zero-period base acceleration. Recent studies (Veletsos (1974 and 1984), Veletsos and Yang (1977), Veletsos and Tang (1989), Haroun and Housner (1981), have shown that for typical tank designs, the frequency for this fundamental horizontal impulsive mode of the tank shell and contained fluid is such that the spectral acceleration may be significantly greater than the zero-period acceleration. Thus, the assumption of a rigid tank could lead to inadequate design loadings. The SSI effects may also be very important for tank responses, and they may need to be considered for both horizontal and vertical motions. The acceptance criteria below are based upon the information contained in TID-7024 and NUREG/CR-1161. Additional guidance is provided in ASCE Standard 4-98, Section 3.5.4. These references also contain acceptable calculational techniques for the implementation of these criteria. The use of other approaches meeting the intent of these criteria can also be considered if adequate justification is provided. A. A minimum acceptable analysis must incorporate at least two horizontal modes of combined fluid-tank vibration and at least one vertical mode of fluid vibration. The horizontal response analysis must include at least one impulsive mode in which the response of the tank shell and roof are coupled together with the 3.7.3-7 Revision 3 - March 2007 portion of the fluid contents that moves in unison with the shell. In addition, the