Strength of Fabricated Joists with Flanges of Minimally Machined Whole Or Half Stems of Lodgepole Pine

When loaded at 7 to 10 percent moisture content in edgewise flexure, over a 15-foot span, with load points 40 inches apart and symmetrical about the midlength of the joist, 9.59-inch-deep lodgepole joists with 4-inch half-round flanges (edged to 3.4-in. width) and flakeboard webs carried significantly more load at failure than did Douglas-fir and larch 2 by 10’s and 2 by 12’s, and 9-1/2-inch-deep joists fabricated with parallel-laminated Douglas-fir veneer flanges. Moreover, they had significantly less deflection than 2 by 10’s and joists with laminated-veneer flanges, and were equal in stiffness to 2 by 12’s. At 3.0 pounds per lineal foot (ovendry basis), these lodgepole joists were intermediate in weight between the 2 by 10’s and 2 by 12’s, which weighed 2.7 and 3.3 pounds per lineal foot respectively, but heavier than the joists with laminated veneer flanges, which averaged only 1.7 pounds per lineal foot. All of the lodgepole joists tested (with 2-in. round, and 3- or 4-in. half-round flanges) were significantly stronger and stiffer than the 2 by 10’s. Lodge-pole joists with 2-inch round flanges and plywood webs (2.4 lb. per lineal foot) and lodgepole joists with 3-inch half-round flanges and plywood or flakeboard webs (2.3 and 2.5 lb. per lineal foot, respectively) weighed less than the 2 by 10 fir and larch joists.

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