Storm Shelter Design
Reese Hundley, Sean Mallory, Heidi Stair, Kaite Whitehurst
A tornado is defined as a rotating column of air that extends from the ground to a cumulonimbus cloud bank that has the capability of causing catastrophic danger to structures. Tornadoes can be categorized based on the enhanced Fujita Scale. Tornadoes generally travel in a southwest to northeast direction and are most commonly caused by super cell thunderstorms. EF4 and EF5 tornadoes are extremely rare where the probability of an impacted structure in the Midwestern United States is 0.002%.FEMA (Federal Emergency Management Agency) standards require that a storm shelter must withstand wind loads from extreme events with MRIs up to 20,000 to 100,000 years (FEMA P-361, 6.2.1). Due to the risk of catastrophic damage caused by extreme tornadoes, storm shelters must be built according to certain standards.
The Storm Shelter Senior Design Team has been tasked with designing an above ground storm shelter that utilizes the Weatherboss 412 panel already available from BRB Roofing as the primary building material of the storm shelter.
Scope of Work
To design a safe, cost effective, and quickly manufactured above ground storm shelter with BRB’s metal roof materials to be implemented into their business.The shelter must use the metal roofing materials provided by BRB Roofing. The panels used in the design must be the current panel dimensions of the Weatherboss 412 panel. The panel thickness will be 18 gauge with a yield stress of 50 ksi. The shelter must be small enough to fit inside a small room in a house or garage with a previously established concrete foundation. Due to pressure changes in the event of a tornado, a vent must be placed in the shelter. The vent will allow for sudden pressure changes to equalize the pressure in the shelter to prevent the shelter from exploding or imploding, as well as provide ventilation to allow those using the shelter to breathe comfortably. The shelter must meet FEMA Test Standards. The FEMA Test Standards state that the structure must withstand a wind gust of 250 miles per hour for three seconds. The structure must also withstand impact by a plank of wood with dimensions two inches tall (nominal) by four inches wide (nominal) by six feet long (2”x4”x6’) that weighs 15 pounds. The plank must travel 100 miles per hour horizontally, and 67 miles per hour vertically when impacting the structure.