47.5 MB - The Whole Building Design Guide

Structural system: Structural damage (e.g., roof deck blow-off, blowoffor collapse of the roof structure, collapse of exterior bearingwalls, or collapse of the entire building or major portions thereof)is the principal type of damage that occurs during strong and violenttornadoes (see Figure 3-16).Figure 3-16:The school wing wasdestroyed by a violenttornado. (Oklahoma,1999)Modest wind speeds can drive rain intoexterior walls. Unless adequate provisionsare taken to account for water infiltration(see Sections 3.3.3.1 to 3.3.3.3),damaging corrosion, dry rot, and moldcan occur within walls.3.2.1.2 Ramifications of DamageThe ramifications of building component damage on critical facilitiesare described below.Property damage: Property damage requires repairing/replacingthe damaged components (or replacing the entire facility), andmay require repairing/replacing interior building components,furniture, and other equipment, and mold remediation. Evenwhen damage to the building envelope islimited, such as blow-off of a portion of theroof covering or broken glazing, substantialwater damage frequently occurs becauseheavy rains often accompany strong winds(particularly in the case of thunderstorms,tropical storms, hurricanes, and tornadoes).At the newly constructed gymnasiumshown in Figure 3-17, the structural metal3-26 MAKING CRITICAL FACILITIES SAFE FROM High Wind