Volume 33, Issue 2 (March 2005)
Shear Strength of Structural Composite Lumber Using Torsion Tests
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 (GLT and GLR). Based on orthotropic theory, the shear strength of LSL, LVL, and PSL is 6.43 MPa (TLR), 7.96 MPa (TLT), and 6.82 MPa (TLT), 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.