RED MAPLE LUMBER RESOURCES FOR GLUED-LAMINATED TIMBER BEAMS

This paper presents test evaluation results for red maple structural g lued-laminated (glulam) beams manufactured from two different lumber r esources. Two types of red maple glulam beam combinations were evaluat ed: 1) a glulam combination designed with E-rated lumber in 25 percent of the outer laminations (top and bottom) and visually graded lumber in 50 percent of the center laminations; and 2) a wide-width glulam co mbination with laminations made from nominal 2- by 4- and 2- by 6-inch No. 2 grade lumber laid edge-to-edge having staggered end joints (ter med 2 by 4/2 by 6 glulam combination). The two research studies differ ed in that one study obtained red maple lumber using common sawing pra ctices used for appearance hardwood lumber recovery, whereas the other study exclusively obtained lumber from the red maple log cants that h ad been processed for removal of furniture-grade material. Given these two lumber resources, the test results from the two studies showed th at it was feasible to develop structural glulam combinations made from E-rated lumber that would meet or exceed a target design bending stre ss of 2,400 psi and a target modulus of elasticity (MOE) of 1.8 x 10(6 ) psi. In addition, the 2 by 4/2 by 6 glulam combination exceeded publ ished design stresses for vertically laminated bending strength, MOE i n both the horizontally and vertically laminated orientations, and hor izontal shear stress in the vertically laminated orientation; Based on the results of the 2 by 4/2 by 6 glulam combination, it was determine d that edge gluing the laminations to form wide-width lumber is not re quired to achieve targeted strength and stiffness levels. Data analysi s showed that ASTM D 3737 procedures developed for softwood species ac curately predict beam stiffness and provide conservative bending and h orizontal shear strength estimates for red maple glulam beams. Also, i t was shown that results from ASTM D 143 shear-block tests could be us ed to accurately predict horizontal sheer strength of 2 by 4/2 by 6 re d maple glulam beams.