47.5 MB - The Whole Building Design Guide

3.3.1.1 SiteWhen selecting land for a critical facility, sites located in ExposureD (see Section 3.1.3 for exposure definitions) should be avoided ifpossible. Selecting a site in Exposure C or preferably in ExposureB would decrease the wind loads. Also, where possible, avoid selectingsites located on an escarpment or the upper half of a hill,where the abrupt change in the topography would result in increasedwind loads. 6Trees with trunks larger than 6 inches in diameter, poles (e.g.,light fixture poles, flag poles, and power poles), or towers (e.g.,electrical transmission and large communication towers) shouldnot be placed near the building. Falling trees, poles, and towerscan severely damage a critical facility and injure the occupants(see Figure 3-19). Large trees can crash through pre-engineeredmetal buildings (which often house fire stations) andwood frame construction (which is commonly used for nursinghomes). Falling trees can also rupture roof membranes andbreak windows.Figure 3-19:Had this tree fallen inthe opposite direction, itwould have landed onthe school. Hurricane Ivan(Florida, 2004)6. When selecting a site on an escarpment or the upper half of a hill is necessary, the ASCE 7 design procedure accounts for wind speed-upassociated with this abrupt change in topography.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-33