Shear Strength of Structural Composite Lumber Using Torsion Tests

摘要

Torsion tests were used to determine the shear strength of full-size structural composite lumber (SCL). Eighty-five rectangular specimens of laminated strand lumber (LSL), laminated veneer lumber (LVL), and parallel strand lumber (PSL) were tested. LSL failed along the strand (LT Plane) and in a brittle manner. LVL and PSL failed across the veneer/strand (LR plane) and in a ductile manner. Different failure modes were observed due to the differences in the shear moduli in two longitudinal planes (Gu and G_(LR)). Based on orthotropic theory, the shear strength of LSL, LVL, and PSL is 6.43 MPa (tau_(LT)), 7.96MPa (tau_(LT)), and 6.82MPa (tau_(LT)), respectively. Based on the results of this study, the torsion test is recommended as a standard method for determining the pure shear strength of full-size SCL, since it is the only known test method to date that imposes a state of pure shear stress in the specimens.