Project Manager:
Yasser Korany, Ph.D., P.Eng., P.E., LEED AP, PMP
Technical Experts Involved:
Yasser Korany, Ph.D., P.Eng., P.E., LEED AP, PMP
Incident Description
Snow and wind storm was reported to have caused the wood-framed roof of a large trout hatchery to collapse. Origin and Cause Inc. was retained to investigate and determine the cause of the collapse.
Investigation
A detailed visual examination of the affected structure was carried out and Environment Canada weather data for snow accumulation and wind gust on the day of the incident were reviewed. The adequacy of the roof framing was evaluated against the requirements of the building code in effect at the time of construction.
Cause of Loss
As-built, the roof framing system was already flexible due to lack of bottom ties for the rafters and the trussed members being only face-nailed together. All the connection capacities become substantially reduced in wet service conditions. Origin and Cause Inc. determined that the outward rotation of the east and west exterior walls due to the horizontal thrust of the weight of ice was most likely what triggered the roof collapse. The limited number of ties between the east and west walls were insufficient to resist the horizontal force from the weight of the ice, which was found to be within design limits.
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