47.5 MB - The Whole Building Design Guide

Missile damage is very common duringhurricanes and tornadoes. Missiles canpuncture roof coverings, many types ofexterior walls, and glazing. The IBC doesnot address missile-induced damageexcept for glazing in wind-borne debrisregions. (Wind-borne debris regions arelimited to portions of hurricane-proneregions.) In hurricane-prone regions,significant missile-induced buildingdamage should be expected, even duringdesign level hurricane events, unlessspecial enhancements are incorporatedinto the building’s design (discussed inSection 3.4).Well designed, constructed, and maintainedcritical facilities should experience little ifany damage from weak tornadoes, exceptfor window breakage. However, weak tornadoesoften cause building envelope damagebecause many critical facilities have wind resistancedeficiencies. Most critical facilitiesexperience significant damage if they are inthe path of a strong or violent tornado becausethey typically are not designed for thistype of storm.3.1.3 Wind/BuildingInteractionsWhen wind interacts with a building, bothpositive and negative (i.e., suction) pressuresoccur simultaneously (see Figure 3-4). Critical facilities musthave sufficient strength to resist the applied loads from thesepressures to prevent wind-induced building failure. Loads exertedon the building envelope are transferred to the structuralsystem, where in turn they must be transferred through thefoundation into the ground. The magnitude of the pressures isa function of the following primary factors.Figure 3-4:Schematic of wind-inducedpressures on a building3-8 MAKING CRITICAL FACILITIES SAFE FROM High Wind