Bending and Shear Stiffness of Cross-Laminated Timber Using a Variable Span Bending Test

Abstract Cross-laminated timber (CLT) is a novel wood product composed of lumber layers adhered orthogonally to create a two-way composite plate. The orthogonal orientation of the layers creates bending stiffness in both in-plane directions. However, compared to a solid wood beam, the orthogonal orientation of CLT reduces the shear stiffness in the longitudinal direction. Compared to a solid wood beam of the same material, shear deformation in CLT increases by approximately 30 %. Test methods to evaluate the shear stiffness terms of CLT beams are needed. This article examined two possible methods to obtain the bending and shear stiffness terms of CLT beams: (1) a simultaneous solution of the beam formulas currently tested in the product standard for CLT and (2) a regression method for variable span beams. Both methods produced similar bending and shear stiffness results. The use of a wide range of length-to-depth (L/d) ratios is recommended, with a minimum L/d value less than 10:1. Different loading configurations can be incorporated into the regression method provided that the regression terms are kept consistent. The simultaneous solution is of particular interest since no additional testing is needed beyond the current beam configurations in the CLT product standard.