Mechanical Characteristics of 21-Year-Old Weathered Nailed Joints

Nailed plywood-lumber joints were cut from the sidewalls of portable hog houses of single-skin type construction. The plywood houses had shown remarkable performance after at least 21 years of continuous weathering and periodic dynamic racking. Even after such lengthy abusive use the houses retained a unit or box-like rigidity. Identically paired joints using new nails were prepared and the mechanical behavior of laterally loaded “old” and “new” nail joints compared. Two types of nails were involved: 6d common and 6d box bright wire nails. Weathering and use had a much greater deleterious effect on joint stiffness than strength and the large diameter common nail was less affected than the box nail. Design load-slip curves are suggested for the nails. For the 6d common nail, this test indicates a reduction of but 12 percent in joint stiffness and essentially no loss in strength for laterally loaded weathered joints. Test results of the residual mechanical characteristics of the individual nail joints agree with the overall outstanding structural behavior of the houses from which they were removed.

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