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Practical Engineering: Resisting Tornado Damage, continued

A breach in the garage door opening of this home first pressurized the inside of the garage, resulting in devastating failure of the garage walls and the home's roof. In a similarly built home nearby (bottom), the garage door was bowed outward by the tornado's suction. The door held, preventing further damage to the home.

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This plywood-sheathed house (top) fared much better than another home (bottom), which was sheathed with non-structural rigid foam board. Rigid foam offers no racking resistance, and little resistance to damage from flying debris.

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Vinyl siding and extruded polystyrene sheathing were no match for flying debris, which pierced holes in this dormer.

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By contrast, the plywood sheathing on this home remains intact, although the vinyl siding is in tatters. Though this OSB sheathing also fared well, it couldn't completely stop a flying pipe.

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An initial breach at a large window resulted in internal pressurization and loss of the roof structure over the vaulted ceiling of this stairway. The rafters had been toenailed in place.

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Here, in a home still under construction, a breach resulted because a pair of French doors were poorly fastened into the rough opening.

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The hold-down anchors weren't adequate to keep this home from shifting 5 feet off its foundation.

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The anchor bolts in this slab-on-grade foundation below were located 20 feet on-center and had no washers; none of the structure was left.

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