Aerodynamics of low-rise buildings in atmospheric turbulence

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Economic and insured losses due to severe storms continue to grow, both in Canada and around the world. The hurricanes this past summer, which destroyed the infrastructure on several Carribean islands, emphasize what is at stake. The majority of the damage to buildings in severe wind storms is to houses, which are the most common structures. Cladding systems and roof components are particularly vulnerable, noting that the failure of a single roof panel can lead to significant losses because of rainwater entry. For large-scale storms such are hurricanes, methods for determining the wind loads acting on the structural systems of buildings using boundary layer wind tunnels with scale models are well established. However, methods for obtaining wind loads for building components such as cladding systems are still unresolved. For tornadoes, which are just beginning to be considered in design by various communities, little is known about the building aerodynamics even though design guidance is needed. The long-term objective of the applicant's research program is to mitigate the effects of extreme winds on buildings, particularly houses, in order to reduce the losses associated with these storms, for the benefit of all Canadians and, in fact, people around the world. Short-term objectives associated with this proposal are related to resolving aerodynamic issues with respect to obtaining wind loads on building components and cladding systems as well as wind loads in tornadoes. Issues to be examined in the proposed research include how the following affect wind loads on buildings: (i) vertical angle of attack of the wind relative to the roof surface, (ii) vortices in the oncoming flow, (iii) turbulence intensity and scales, and (iv) the geometry of the building edges. Dealing with wind loads on building components and cladding systems in hurricanes (and other large-scale storms) and wind loads in tornadoes require that many of the same issues be resolved. In particular, methods to modify or correct data obtained in one particular turbulent wind field into those appropriate for another are needed and will be developed. An example of this would be applying a method to modify wind loads obtained in the atmospheric boundary layer during a hurricane into what would happen if it were a tornado of similar wind speeds. The research methods involve boundary layer wind tunnel experiments utilizing simultaneous particle image velocimetry and surface pressure measurements. Six graduate students and five undergraduate students will be trained via the proposed research using world-class research infrastructure in a collaborative, international group environment, with opportunities to develop technical research skills, communication skills, along with leadership and teaching opportunities.