Laminating Butt-Jointed Log-Run Southern Pine Veneers Into Long Beams of Uniform High Strength

Twenty laminated beams were constructed of log-run, butt-jointed, loblolly (Pinus taeda L.) pine veneers 1/6 inch thick and 100 inches long. The beams were 18 inches deep, 2 inches wide, and 25 feet long. Veneers were arranged in the beams according to their modulus of elasticity (MOE). The stiffest were placed outermost, and the most limber in the center. The veneers, which were cut on a lathe, ranged in MOE from 510,000 to 2,960,000 psi and averaged 1,690,000 psi. This average was 110,000 psi lower than the accepted species average. The beams had an average effective MOE of 2,110,000 psi. Average modulus of rupture was 9,020 psi, with a 95-percent exclusion limit of 7,170 psi, thus justifying an allowable stress in bending of 3,370 psi. A single beam constructed on the same principle but made from veneers selected to simulate log-run slash pine (Pinus elliottii Engelm.) had an MOE of 2,400,000 psi and an MOR of 10,080 psi. The three butt joints in each lamina did not seriously reduce beam MOE.

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