47.5 MB - The Whole Building Design Guide

Figure 3-80:The antenna tower atthis fire station buckled.Hurricane Katrina(Mississippi, 2005)Electrical service masts: Service mast failure is typically caused bycollapse of overhead power lines, which can be avoided by usingunderground service. Where overhead service is provided, it isrecommended that the service mast not penetrate the roof. Otherwise,a downed service line could pull on the mast and rupture theroof membrane.Satellite dishes: For the satellite dish shown in Figure 3-81, thedish mast was anchored to a large metal pan that rested on theroof membrane. CMU was placed on the pan to provide overturningresistance. This anchorage method should only be usedwhere calculations demonstrate that it provides sufficient resistance.In this case the wind approached the satellite dish insuch a way that it experienced very little wind pressure. In hurricane-proneregions, use of this anchorage method is notrecommended (see Figure 3-82).Lightning protection systems: For attachment of lightning protectionsystems on buildings higher than 100 feet above grade, andfor buildings located where the basic wind speed is in excess of 90mph, see Section 3.4.4.3.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-93