Document: NUREG-0800
Document ID: 274f0789-5956-4979-b7da-3b44ddf985d4
Document Type: srp
Title: TORNADO LOADS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0705/ML070570002.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.3.2
CFR Part: 
CFR Title: 

Content:
und. iii. Design tornado wind loads should be determined in accordance with the following sections in ASCE/SEI 7-05, as applicable. (1) 6.5.12 Design Loads on Enclosed and Partially Enclosed Buildings (2) 6.5.13 Design Wind Loads on Open Buildings with Monoslope, Pitched, or Troughed Roofs (3) 6.5.14 Design Wind Loads on Solid Freestanding Walls and Solid Signs (4) 6.5.15 Design Wind Loads on Other Structures C. Atmospheric Pressure Change Effects RG 1.76 provides guidance for determining the pressure drop and the rate of pressure drop caused by the passage of a tornado. “Wind Effects on Structures: Fundamentals and Applications to Design,” (Third Edition, John Wiley and Sons, Inc., New York, 1996.) by E. Simiu and R. H. Scanlan, provides methods for determining loads on structures due to atmospheric pressure changes during the passage of a tornado. For a structure that is completely open subjected to a tornado, the internal and external pressures on the structure equalize rapidly during the passage of the tornado. Therefore, the atmospheric pressure change between the interior and the exterior of that structure approaches zero. For a structure that is enclosed (unvented structure), the internal pressure remains equal to the atmospheric pressure before the passage of a tornado. The atmospheric pressure outside the structure changes during the passage of a tornado, which creates pressure differences between the interior and the exterior of that structure, and these differential pressures produce outward acting loads on the roof and walls of the enclosed structure. For a structure that is partially enclosed (vented structure), the determination of loads on the structure due to atmospheric pressure changes during the passage of a tornado is more complicated. If venting is adopted as a way to reduce the atmospheric pressure change effect on a structure, the review will be performed on a case-by-case basis. D. Tornado-Generated Missile Impact Effects