Benchmark Study of Tornado Wind Loading on Low-Rise Buildings with Consideration of Internal Pressure

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Tornadoes are historically among the most devastating natural hazards in the United States, as observed by the damage and fatalities during recent major tornadoes, including the Joplin, Missouri and Tuscaloosa-Birmingham, Alabama tornadoes in 2011, the Moore, Oklahoma tornado in 2013, and the Dallas, Texas area tornado in 2015. As post-tornado disaster surveys have repeatedly revealed, tornado-induced losses and fatalities are often due to damage to low-rise buildings. A critical factor contributing to such building damage is that many low-rise buildings are designed only for winds that travel mostly along a straight line near the earth's surface, and not for the rotating tornado winds that are potentially more damaging, primarily due to inadequate understanding of tornadoes and tornado wind loading on structures. The goal of this research is to formulate computational models that comprehensively characterize rotating tornado wind loading and the impact of such wind loading on low-rise buildings. Such models can be used by engineers to conduct performance-based evaluation of low-rise buildings subjected to tornado hazard as a way to reduce damage and fatalities. To raise awareness of the impact of natural hazards, including tornadoes, on buildings and communities, this research will be integrated into education and outreach activities within existing programs at Texas Tech University (TTU), such as courses offered by TTU's National Wind Institute Wind Science and Engineering Ph.D. program and ongoing outreach activities, including a 4-H Mentoring Program, Science Camp, and Lubbock's Annual Severe Awareness Day. To achieve this research goal, this project will test models of low-rise buildings with two roof types in various types of tornadic vortices simulated in a large-scale tornado simulator at TTU and straight-line winds simulated in the NSF-supported Natural Hazards Engineering Research Infrastructure (NHERI) boundary layer wind tunnel at the University of Florida to provide two benchmark datasets. These two datasets will be used to quantify the differences between the loadings by tornado and boundary-layer-type straight-line winds. The focus will be placed on the effects of building internal pressure and the nonstationary and non-Gaussian nature of tornado loading introduced by the translation of spatially varying wind speed and static pressure deficit in tornado vortices. On this basis, an innovative approach based on discrete wavelet transform and Gaussian filtering will be used to characterize, model, and simulate nonstationary, dynamic tornado wind loading on low-rise buildings to enable probabilistic evaluation of the loading effects. Project data will be made available in the NHERI Data Depot at https://www.designsafe-ci.org/.