Design wind loads for houses in tornadoes

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Economic and insured losses due to severe storms continue to grow, both in Canada and around the world. Canada is vulnerable to severe wind storms, with significant examples being the Barrie tornado in 1985 (12 lives, $300M), the Edmonton tornado in 1987 (27 lives, $670M), and Hurricane Juan in 2003 (8 lives). Wood-frame houses, our most common type of structure, are vulnerable because of the fact that most houses are not engineered and have limited wind-resistant features. The primary safety issue pertains to keeping the whole house on the foundation, and the roof connected to the walls. When this is achieved, loss of life and economic losses are minimized. Wind effects on houses in large-scale storms, such as hurricanes, are now reasonably known because of many years of wind tunnel studies and, more recently, structural testing of full-scale structures along with building components and materials. It is well established that enhanced building codes can reduce losses in these storms. In contrast, wind loads on houses in tornadoes are largely unknown. Notwithstanding the fact that design to mitigate losses in tornadoes is only just beginning to be discussed due to the ever increasing losses, the fact that there are few facilities which can create tornado-like vortices of large enough size that buildings can be tested has also been a barrier. This has changed recently, with the development of the WindEEE Dome. The objective of this proposal is to use this facility as a basis to determine design wind loads for wood-frame houses in tornadoes. In particular, the effects of the (i) shape of the house, the (ii) surrounding terrain and (iii) neighbourhood patterns, along with the (iv) static-pressure drop and internal pressures, on wind loads will be examined in the presence tornado-like vortices. Design wind loads will be based on using a series of factors for each of these parameters, relative to those currently used in building codes. This approach will simplify design for practicing engineers and allow codes to be modified as other factors become more well understood. At least five students will be trained during the course of this investigation.