Document: NUREG-0800
Document ID: df28a5de-563d-4e9d-89a2-3436e072c82c
Document Type: srp
Title: TORNADO LOADINGS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052340625.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.3.2
CFR Part: 
CFR Title: 

Content:
all be the most severe wind that has been historically reported for the site and surrounding area with sufficient margin for the limited accuracy, quantity, and period of time in which historical data has been accumulated. 2. The acceptance criteria for the tornado wind velocity, the differential pressure and its associated time interval, the spectrum of tornado- generated missiles and their characteristics, and the bases for deter- mining these parameters, are established by the Accident Evaluation Branch (AEB) as described in SRP Sections 2.3.1, 2.3.2, and 3.5.1.4. The approved values of these paramenters should serve as basic input to the review and evaluation of the structural design procedures. 3. The acceptance criteria for the procedures used to transform the tornado parameters into effective loadings on structures are as follows: a. For transforming the tornado wind velocity into an effective pres- sure applied to structures, the criteria delineated in either the American Society of Civil Engineers (ASCE) Paper No. 3269, "Wind Forces on Structures" (Ref. 2), or in ANSI A58.1, "Building Code Requirements for Minimum Design Loads in Buildings and Other Structures" (Ref. 3), are, in general, acceptable. In particular, the following shall apply: (i) The maximum velocity pressure, p, should be based upon the maximum tornado velocity, V, using the following formula: p = 0.00256 V2 psf, in which V is in mph. (ii) The velocity pressure should be assumed constant with height. (iii) The maximum velocity pressure, p, applies at the radius of the tornado funnel at which the maximum velocity occurs. The tan- gential velocity varies with the radial distance from the center of the tornado core. The variation may be considered in accord- ance with that described in the paper, "Tornado Resistant Design of Nuclear Power Plants" (Ref. 4). 3.3.2-2 Rev 2 - July 1981 (iv) For calculating velocity pressures on external surfaces of struc- tures, on external portions thereof, and on