UA Debris Cannon Attacks High Winds Damage

For those who experienced the April 27, 2011 EF-4 Tuscaloosa tornado personally, the event serves as a lifelong memory. For one University of Alabama graduate and now faculty member, the twister serves as an impetus to doing something to affect the impact of future storms.

Dr. Patrick “Shane” Crawford, an assistant professor in the civil, construction and environmental engineering department, was a UA junior in civil engineering when the deadly tornado leveled 12% of the City of Tuscaloosa 15 years ago today. He witnessed the storm's fury and saw it's aftermath. Crawford now is in a position to help mitigate the damage done by future tornadoes and hurricanes.

Dr. Crawford focused his graduate research on the resilience of communities that face natural hazards, an issue that city leaders and emergency managers have wrestled with for years.

“I sought to look at not only reducing the impact of the damage but also understanding how the direct impact to physical infrastructure affects social systems, economic systems and communities,” Crawford said. “I wanted to understand the cascading effect these natural hazards have on all of the interdependent systems within a community and share that information with the public so that local decision-makers could understand how the hazard mitigation policies they make affect the trajectory of the community.”

Communities that lack adequate storm shelters are especially at-risk during tornado events. Mobile home parks, in particular, are at heightened risk, as these structures are often not anchored and can be easily destroyed by tornadoes. Moreover, cities and counties without advanced early warning systems face increased danger. The ability to receive and act on a tornado warning can mean the difference between life and death. Building community resilience also involves urban planning that considers tornado risks and encourages the construction of safe structures. There are too many substandard structures, particularly in regions like Alabama that are prone to destruction by violent storms.

Professional tornado shelter installation costs run between $2,892 and $13,281 depending on the shelter type, size, and location. For most people that is cost prohibitive. That has prompted the Federal Emergency Management Agency (FEMA) and other organizations to encourage states and jurisdictions in tornado and hurricane prone regions like "Dixie Alley" and the Gulf Coast to adopt more stringent building codes. This makes surviving dangerous, high-wind events, more cost effective. FEMA states this can save $11 in damage repairs for every $1 invested.

“Historically, engineers were never required to design buildings for tornadoes, but in recent years that has changed due to new science provided by tornado researchers," says Dr. Crawford.

After stents with the National Institute of Standards and Technology and FEMA, Crawford has returned to UA and is doing research related to building codes, analyzing structures in countless cities after storms to determine if they are meeting performance levels or if their designs need to be updated.

Crawford uses the world's only quad-barrel debris cannon to simulate wind-borne debris which causes damage to structures during severe weather events. The cannon launches projectiles, such as wooden planks, at high speeds to test the impact resistance of storm shelters and building materials. These pneumatic devices help researchers develop safer, wind-resistant structures and enhance public safety against flying debris.

In addition, Dr. Crawford analyzes the barriers, such as cost and education level, that might prevent residents from constructing or purchasing a storm shelter for their homes.

Combined with research being conducted by fellow UA faculty Dr. Sriram Aaleti and Dr. Armen Amirkhanian, progress is being made.

With more frequent and more powerful storms occurring it is critical to provide more structurally sound, survival buildings and shelters. Crawford is coordinating with researchers across many other disciplines covering social science, economics, insurance, and public policy to tackle this issue from a broad perspective. As losses from natural hazards continue to grow and disrupt communities, understanding how to build communities and what measures can be taken to mitigate future damage in a cost-effective manner to sustain social functions will be increasingly important.