Tornado papers Wind Loads on Houses: Destructive Model Testing of a Residential Gable Roofed House B. Visscher G.A. Kopp P.J. Vickery March 24, 2004 ICLR Research - Paper 37
In August 1992 Hurricane Andrew struck southern Florida. Thirty people died and 250,000 were left homeless. Damage from this Category 4 hurricane was estimated at 30 billion dollars . After this storm, there was a strong interest to identify the type of damage associated with the large insurance costs. Residential subdivisions located in this region that were relatively unsheltered from the full force of the storm incurred the most damage. The damage to these houses presented a unique opportunity to investigate the type and extent of damage to this type of structure.
Major roof failure was the single most common and abundant type of damage. The investigation concluded that the main types of roof failure were: 1. local failure (loss of sheathing); 2. discrete roof truss failure; and 3. global roof failure (whole roof) due to roof-to-wall connection failure. In the high damage areas, sheathing failures were the most common type of roof failure recorded.
In the current study, a 1:20 scale destructive model of a low-rise gable roofed house was tested in the Boundary Layer Wind Tunnel Laboratory at the University of Western Ontario. The goal was to study the failure of roofs and roof elements. The term ‘destructive’ is used to describe the model because it was designed to fail in the wind tunnel. Both local (roof sheathing panel) and global (whole roof) failures were investigated. A number of different variables were studied to determine their effects on roof and roof panel failure, such as: dominant openings and their location with respect to the wind direction, background leakage, roof-to-wall connection strength, roofing panel hold down strength, the ratio of ridge and soffit vent area to the roof area, and the presence or absence of sheathing panels. The trajectory of airborne sheathing panels (after local roof failure) was studied as in a severe wind event airborne debris from damaged buildings could cause damage to neighbouring structures.