Grant: Discovery Grants Program - Individual

Damage and economic losses due to severe storms continue to grow exponentially in Canada due to population growth and climate change. A large proportion of these losses are to buildings under extreme wind. While Canada has excellent building codes, there are significant gaps in design requirements for thunderstorm winds, such as tornadoes and downbursts, which are not considered. The applicant's research program is focussed on reducing losses to buildings from such storms. This involves identifying and documenting the damage and failures to buildings (using post-storm field studies), determining the capacities and responses of building systems under extreme loads, and determining the aerodynamic loads. The objective of this proposal is to develop an improved understanding of building aerodynamics in tornadoes. The detailed objectives include examining the effects of turbulence near the building, the effects of the swirling motion of tornadoes, and the effects of tornado translation speed, which causes rapid changes in wind speed as the tornado passes the building. All of this is done to develop aerodynamic models of buildings that could be used for tornado design in building codes and in wind tunnel test methods. The methods used to meet the detailed objectives primarily involve wind tunnel testing. In the experiments, velocities and pressure forces on the buildings will be measured. At least 7 students will be trained from the funding provided by this grant. Over the longer term, the expected impact will be to contribute to reduced losses and damage and increased safety from severe storms. This will be achieved primarily through improved building codes and building-product design standards. The expected impact of this proposal will be to improve the fundamental understanding of winds storms on the aerodynamic loads on buildings. These will directly affect engineering design load standards including Part 4 of the National Building Code of Canada, and the ASCE 7 Standard "Minimum Design Loads and Associated Criteria for Buildings and Other Structures." This work is also expected to lead to changes to the ASCE 49 Standard "Wind Tunnel Testing for Buildings and Other Structures". Finally, it is worth pointing out that wind speeds in tornadoes are rarely measured directly; rather, they are based on assessing their damage. Thus, the assessment of tornado intensity is based entirely on what they encounter in their path. For example, if a tornado only travels over an open field, the actual wind speed cannot be determined. If it travels through a suburban neighbourhood, it will be rated based on the structures it encounters and damages, which would be primarily houses. Therefore, the improved understanding of effects of tornadic wind fields on buildings developed in this proposal will also impact wind speed estimation techniques for tornadoes, when combined with a details of various failure mechanisms of buildings.