Stress distribution in structural composite lumber under torsion

Stress distribution in fall-size, structural composite lumber (SCL) under torsion was analyzed using finite element analysis (FEA). The objective was to determine shear strength of SCL using orthotropic torsion theory and compare the results to experimental results. The commercial finite element program ANSYS was used to perform the analysis using orthotropic material properties. A three-dimensional, eight-node brick element was used to model the specimens. The FEA showed that SCL is more orthotropic in material behavior than solid-sawn lumber and orthotropic torsion theory should be used to determine the shear strength of SCL. The degree of orthotropicity depends upon two shear moduli in longitudinal-tangential and longitudinal-radial planes. The shear strength based on orthotropic FEA was within 2 percent of experimental results.