Institute for Transportation

A red oak glued-laminated beam combination was developed to achieve a bending strength of 16.5 Mpa (2,400 psi) and a modulus of elasticity of 12.4 GPa (1.8 ÌÑ 106 psi). Thirty beams of two sizes were evaluated to determine the adequacy of ASTM D 3737 (ASTM, 1992a) procedures for prediction of glued-laminated beam design stress and stiffness, and to verify the volume effect equation currently in use. Lumber properties were recorded prior to beam manufacture for use in the ASTM D 3737 analysis. Data were analyzed using both knot data collected for each lamination grade, and for the pooled knot data of combined lamination grades to increase knot data sample size. Beam data were normalized to distinguish the difference in bending strength due to volume effect from the difference in bending strength due to lumber properties. Beam strengths from pooled knot data were not normalized. Beam tests indicate that ASTM D 3737 can be used to satisfactorily predict the strength and stiffness of red oak glued-laminated beams, and that the current volume effect model adequately predicts the behavior of red oak glued-laminated beams.
Keywords. Red oak, Glued-laminated beams, Strength, Stiffness, Volume-effect.