BUILDING RESILIENCE TO HIGH WINDS USING FRAGILITY ANALYSIS
North America gets hit with approximately 1,100 recorded tornadoes annually. In Ontario, Canada, more than 12 tornadoes are recorded between the months of May and September annually. Two major tornadoes hit Ottawa, Canada on September 21, 2018. Ottawa, Ontario suffered an Enhanced Fujita (EF 3and EF2) tornado in Dunrobin and Arlington Woods, respectively. These severe events destroyed numerous buildings, and thus, a field investigation was conducted to observe the damages in the structures. Damage-assessment data was recorded with a focus on damage failure modes and functionality of the buildings during the field investigation. According to the data collected, the damage was characterized based on different levels and discussion was formulated surrounding the way residential buildings should be built to assure resilience against tornadoes. Based on the site investigation, it was found that roofs are the most vulnerable component of a residential house and are often left with rafter, sheathing and shingle damages when exposed to high wind pressures. Fragility analysis can be used to estimate the probability of failure of a roof when constructed with specified nails and sheathing sizes. Specific type of nails, roof to wall connection details and sheathing sizes based on the damaged roofs that were previously assessed in the Dunrobin area in Ottawa,Ontario. Empirical fragility analysis considers eight different scenarios, including different sheathing and nail sizes. These baseline structures were used to analyze how different variables in a wooden roof could affect the fragility analysis results. The considered variables included the nail type, panel size, wind load and dead load. Finally, Finite element analysis (FEA) was conducted using the ABAQUS software to model and determine the structural responses of typical residential roofs. The wood-framed roof models permitted visualtion of the structural behaviour under wind pressures such as excessive stresses. The FEA model results were then compared to the results from a field investigation in Dunrobin, Ontario. This methodology will allow for a more accurate prediction of tornadic wind-induced damage on residential roofs to be used for better design and construction practices. The performance of the examined buildings from the field investigation, the fragility models and the initial ABAQUS models, suggests a need for more resilient design and retrofit methods to strengthen buildings envelopes.
URI for this recordhttp://hdl.handle.net/1974/28743
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