Residential Damage Patterns Following the 2011 Tuscaloosa, AL and Joplin, MO Tornadoes

Damage survey data was collected following the destruction caused by tornadoes in Tuscaloosa, AL and Joplin, MO that together destroyed over 13,000 buildings, caused over $5 billion in economic losses and left 226 persons dead. Using geotagged photographs for 1,814 residential structures in the two cities, damage ratings were assigned using the Enhanced Fujita Scale and mapped for each building, in an effort to establish the wind field for each tornado. The results depict the physical distribution of the damaging forces away from the centerline of the tornado. The spatial distribution of wind velocities estimated using the EF-Scale were in agreement with measured wind velocity distributions using Doppler radar in other violent tornadoes. A second part of the study identified common failure mechanisms within a data set of 365 light-framed wood residential structures from the Tuscaloosa tornado. The results of this analysis showed that tornado forces rapidly attenuate with distance away from the center of the tornado, as EF-ratings can be reduced from EF-4 to EF-2 within 100 meters. In addition, the seven most prevalent failure mechanisms were identified and the correlations among them are presented. Catastrophic failures are most common at or near the center of the tornado's path (below the vortex). Buildings further away from the center experience damage patterns that are similar to structures subjected to straight-line hurricane force winds. These field studies and analyses are being used to inform the development of full-scale structural testing wall components with the goal of developing structural retrofits and improving design practices for tornado-resilient houses.