Mechanical properties of laminated strand lumber and hybrid cross-laminated timber

• Hybrid CLT was fabricated using lumber and/or LSL.
• The bending properties of generic CLT were improved by using LSL as core or outer layers.
• Planar shear failure in lumber core layer was the key failure mode of CLT with a lumber cross layer.
• Tension failure in bottom layer was the key failure mode of CLT with a LSL core layer.

Hybrid cross laminated timber (HCLT) was fabricated using lumber and/or laminated strand lumber (LSL), the mechanical performances of which were evaluated. To reach this goal, the mechanical properties of LSL and the bending properties of CLT and HCLT were measured in this study. The properties of LSL measured included the tension strength (only in the major direction), shear strength, shear modulus, and modulus of elasticity (MOE) and modulus of rupture (MOR). The failure mode of each kind of specimens was visually examined and recorded. Four types of CLT panels, one generic CLT (used as control) and three types HCLT were fabricated. The properties measured included the bending properties (in the major direction) and planar shear properties (in both major and minor directions). It was found that the HCLT had better bending and planar shear properties than that of generic CLT. The MOE and MOR of HCLT having LSL as the outer layers were 19% and 36% higher than those of generic one, respectively. The MOE and MOR of HCLT having LSL as core layer (replacing the cross lumber layer) were 13% and 24% higher than that of generic CLT, respectively. The failure modes of four types of CLT observed included the planar shear failure of cross lumber layer, tension failure of bottom LSL, and tension failure of bottom lumber, especially tension failure of lumber originated at a knot(s).