6 Natural Hazard Design and Analysis Other than Earthquake
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Published:2006
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The structural loads associated with extreme straight and hurricane wind velocities have usually been considered statically applied and distributed in accordance with the American Society of Civil Engineers (ASCE) 7-05 Standard for buildings and other structures to include chimneys, tanks and rooftop equipment [1] or ACI-307 [2] for concrete stacks and STS-1-2000 [3] for steel stacks.
Tornado wind effects as a design-basis load have generally not been defined or required for consideration in design as a normal or severe load as defined in Chapter 3. They have been prescribed as an extreme load for nuclear safety-related structures. In some cases they have also been considered for petrochemical facilities in tornado-prone regions, but this has not become a standardized design practice associated with hazardous, petrochemical or biomedical facilities. As a result a tornado wind field and the methods used to combine the effect of wind or “dynamic pressure” and the associated reduced atmospheric pressure to include building openings and potential airborne missile effects have not been defined in general industry standards for design purposes, except as applied to the nuclear industry. A rational yet simple combination of the wind field and reduced atmospheric pressure effects for use in analysis and design or evaluation of structures subject to design-basis tornado loadings is presented in this chapter. There is also a suggested procedure for including the effect of postulated, straight, hurricane and tornado-borne missiles in structural design in this chapter as well as in Chapter 8.