Are Present Wall Constructions Structurally Sound?

Tests were made by the U.S. Forest Products Laboratory to determine racking resistance to horizontal forces of several types of house wall construction. Wall panels tested were 8 feet by 8 feet, and 8 feet by 12 feet, constructed of full size lumber members. Panels were fastened in place by means of a hold-down strip at the free bottom and a hold-down rod at the loaded end to prevent uplift. Loads were applied horizontally at the top corner of the panel. Loads were removed and residual deflection measured for each increased load, and loads were increased until failure or until the top plate of the panel was deflected 6 inches. A panel with lumber sheathing nailed horizontally on studs 16 inches on center with a single 1-inch by 4-inch let-in 45? brace was used as a standard for comparison. A similar panel, with the 1 by 4 brace extending across only three studs, often used next to doors, failed at 35 percent less load than the standard panel. Panels with similar construction but with a two-piece symmetrical K-brace failed at approximately 45 percent of the load for the standard panel. An unsymmetrical K-brace (one short piece and one long piece) was somewhat longer than the symmetrical K-brace panel. Panels with vertical siding applied to 1-inch by 4-inch diagonal boards nailed to studs 24 inches on center had from 65 to 95 percent of the strength of standard panels, depending on whether the diagonal braces were placed in tension or in compression. One panel tested had a 6- by 8-foot 1/4-inch-thick plate glass window centrally located in an 8-foot by 12-foot panel, the window was flanked by 2-foot-wide panels of 1/4-inch plywood. This panel failed by buckling of the plywood at about 40 percent of the maximum load carried by the standard panel, but the glass was not damaged. A post and lintel wall tested about 10 percent stronger than the standard panel. This wall consisted of T-shaped posts made by nail-gluing a 2 by 2 to a 2 by 4 member; posts were nailed to a 2- by 6-inch bottom plate, and to a top plate (lintel) consisting of a 2 by 4 nailed to a 2 by 8 member; openings between post and plates were filled by 4-foot by 8-foot panels comprised of 1/4-inch thick cement asbestos facing bonded to each side of an insulating fiberboard core.

You must be logged in to download any documents. Please login (login accounts are free) or learn how to Become a Member