Measurement of rolling shear modulus and strength of cross-laminated timber using bending and two-plate shear tests

Rolling shear properties of cross-laminated timber (CLT) are very low because of the configuration of the cross layer. In some applications, they are the key properties that govern the design and application of CLT. To explore an appropriate method for assessing the rolling shear properties of CLT, variable span bending tests and two-plate shear tests were conducted. Three types of down-scaled black spruce (Picea mariana) specimens, including wooden cross layer (WCL), steel-wood-steel (SWS), and three-layer down-scaled CLT (wood-wood-wood [WWW]), were fabricated using onecomponent polyurethane (for edge gluing) and epoxy adhesive (for steel and wood bonding). Deflection of a WWW specimen was predicted using a shear analogy method based on rolling shear modulus (Grt) of the cross layer obtained from the variable span bending test and two-plate shear test methods and was then compared with the deflection directly measured on WWW specimens. The test results showed that rolling shear modulus of WCL from the two-plate shear test was 72.61 MPa, which was more than twice that of the cross layer of SWS from the variable span bending test. Rolling shear strength of WWW measured using the three-point bending method was 2.74 MPa at a span-to-depth ratio of 6. © 2014 by the Society of Wood Science and Technology.