Project Manager:

Amir Jamshidi, Ph.D., P.Eng., P.E.

Technical Experts Involved:

Yasser Korany, Ph.D., P.Eng., P.E., LEED AP, PMP
Amir Jamshidi, Ph.D., P.Eng., P.E.

Client Testimonial:

“Thank you so much for this very comprehensive report that has helped us understand the situation pertaining to the building and also the claim presented by our Insured.”

Incident Description

A 96’ long by 48’ wide by 16’ high pre-engineered farm building located near Regina in Saskatchewan was lifted 2” on one side during a windstorm. This incident was the third time in a 5-year period that upward movement due to wind was reported for the same farm building. Origin and Cause Inc. was retained to investigate the root cause of the repeat wind damage.

Investigation

A detailed visual examination of the farm building was carried out and as-built drawings were prepared. The adequacy of the vertical and lateral load resisting systems was evaluated by comprehensive structural analyses using available weather data for wind gusts for the month of the event. The resistance of the wood posts and foundation was estimated, and the uplift forces developed from wind pressures were analyzed.

Cause of Loss

Based on available historical climate data, wind pressures sustained by the farm building never exceeded the specified wind pressure the building should have been designed to resist. Our investigation identified significant pre-existing structural deficiencies that rendered the building particularly vulnerable to twisting and uplift under wind including: the absence of proper bracings for wind resistance, high eccentricity under wind pressure due to a large sliding door opening on one of the short end walls, and the lack of footing for the wood posts which were embedded in ground.

The imbalance between the stiffness of the end walls resulted in the development of torsional moments (twisting of the building) under wind pressures acting on the longitudinal walls. Because the posts were not tied down to footings, the twisting of the building under wind pressure lifted the posts on the windward side and compressed the ones on the leeward side.