Mechanical Properties of Southern Pine Cross-Laminated Timber

Abstract

Cross-laminated timber (CLT) is a novel wood building material suitable for floor, roof, and wall assemblies in low- and mid-rise construction as an alternative to concrete and steel. CLTs are considered to provide good seismic resistance, fast erection times, carbon sequestration, and a significant reduction in greenhouse gas emissions over other construction materials. Southern pine is an abundant forest resource; yet it has not been commercially used for CLT manufacturing. The purpose of this paper was to measure the bending and shear properties of CLT material fabricated using southern pine lumber compared to product standards. Bending strength, bending stiffness, shear strength, resistance to shear by compression loading strength, and resistance to delamination were measured according to product standards, and test results were compared with values given in the standards. Bending tests were conducted on jointed beams due to test length requirements. Bending strength, bending stiffness, and wood failure in resistance to shear by compression loading tests exceeded the published values for the published values, while resistance to delamination did not meet the established criteria. The resistance to delamination results may have been affected by the uncontrolled moisture content of the lumber during fabrication of the CLTs. The application of glued laminated lumber standards to CLT products requires clarification in the orientation of loading directions for the resistance to shear by a compression loading test and the measurement of all four sides of the resistance to delamination specimens. Increased scrutiny of moisture content quality control is highly encouraged for the production of CLTs.