47.5 MB - The Whole Building Design Guide

Strong and violent tornadoes can generate very powerful missiles.Experience shows that large and heavy objects, including vehicles,can be hurled into buildings at high speeds. The missile stickingout of the roof in the foreground of Figure 3-103 is a double 2-inch by 6-inch wood member. The portion sticking out of the roofis 13 feet long. It penetrated a ballasted ethylene propylene dienemonomer (EPDM) membrane, approximately 3 inches of polyisocyanurateroof insulation, and the steel roof deck. The missilelying on the roof just beyond is a 2-inch by 10-inch by 16-foot longwood member.Figure 3-103:A violent tornadoshowered the roof ofthis school with missiles.(Oklahoma, 1999)There is little documentation regarding tornado-induced damageto critical facilities. Most of the damage reports available pertainto schools because schools are the most prevalent type of criticalfacilities and, therefore, are more likely to be struck. A 1978 reportprepared for the Veterans Administration 13 identified fourhospitals that were struck by tornadoes between 1973 and 1976.Table 3-5 (taken from that report) further illustrates the effectstornados can have on critical facilities.13. A Study of Building Damage Caused by Wind Forces, McDonald, J.R. and Lea, P.A, Institute for Disaster Research, Texas Tech University, 1978.MAKING CRITICAL FACILITIES SAFE FROM High Wind3-127