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:
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 internal surfaces, where there are openings in the structure, appropriate shape coefficients shall be used in accordance with ASCE Paper No. 3269 (Ref. 2). Gust factors may be taken as unity. b. If venting of a structure- is adopted as a design measure to permit transforming the tornado-generated differential pressure into an effective reduced pressure, the acceptance criteria are established on a case-by-case basis, upon request, by the Auxiliary Systems Branch (ASB). c. The acceptance criteria for transforming the tornado-generated mis- sile impact into an effective or equivalent static load on structures are delineated in subsection II of SRP Section 3.5.3. d. Having established the effective loads for each of the above three individual tornado-generated effects, the combination thereof should then be determined in a conservative manner for each particular structure, as applicable. An acceptable method of combining these effects is as follows: i) Wt = WW (ii) Wt = W (iii) Wt = WM (iv) Wt Ww + .5 Wp (v) Wt =Ww + Wm (vi) Wt= Ww + .5 Wp + WM where: Wt total tornado load, Ww ..... tornado wind load, W ..... tornado differential pressure load, and p Wm ..... tornado missile load. For each particular structure or portion thereof, the most adverse of the above combinations should be used, as appropriate. These combined effects constitute the total tornado load which should then be combined with other loads as specified in SRP Sections 3.8.1, 3.8.4, and 3.8.5. 4. The information provided to demonstrate that failure of any structure or component not designed for tornado loads will not affect the capability of other structures or components to perform necessary safety functions, is acceptable if found in accordance with either of the following: a. The postulated collapse or