Throughout the United States, hundreds of tornadoes and several hurricanes affect people’s livelihoods each year. Nearly every state east of the Rocky Mountains faces the possibility of devastating tornadoes, with the Midwest being particularly at risk. Living along the gulf and east coasts offers little respite, as powerful hurricanes are apt to cause similar, and potentially more widespread, damage. The following maps show this sobering possibility. Check out those wind speeds!
These natural disasters not only cause structural damage to property, they also cause numerous injuries, and regrettably, far too many deaths of people caught in their path. When the envelope of a structure is punctured by debris, pressure changes from the wind can cause the structure to rapidly fail. In many areas, buildings were not built with resistance to debris in mind. However, with the extensive media coverage of recent disasters such as the devastating tornadoes in Joplin, Missouri, and Moore, Oklahoma, as well as Hurricanes Katrina and Sandy, greater numbers of home and small business owners are seeking to increase their probability of surviving a storm by voluntarily installing a “safe room” to shelter in.
A safe room is defined by the Federal Emergency Management Agency (FEMA) as “a space where you, your family, or friends and employees can survive a tornado or hurricane with little to no injury.” Guidelines for safe room design are detailed in FEMA P-361, Design and Construction Guidance of Community Shelters, and FEMA P-320, Taking Shelter from the Storm: Building a Safe Room Inside Your Home.
Safe room design must meet two main criteria. The first is that the room’s structural components must be able to withstand the basic wind load of the tornado or hurricane. The second design criterion is that the safe room must have resistance to flying debris, a particular danger of tornadoes and hurricanes.
As part of their ongoing efforts to improve safe room design, James Bridwell, Robert Ross, Zhiyong Cai, and David Kretschmann conducted performance tests on a series of materials and wall designs that might be used in the construction of safe rooms. Next week we will delve into this unique research described by Bridwell and others in the publication, USDA Forest Products Laboratory’s Debris Launcher.