Cross laminated timber (CLT) is a new engineered wood product that has experienced rapid growth and market acceptance for residential and non-residential construction in western and central Europe. Potential exists for rapid market adoption in North America if manufacturing capacities are developed...
Development of cross laminated timber (CLT) manufacturing facilities will require an optimization of manufacturing parameters to ensure efficient production. This study examined the effects of press pressure, press time and the addition of water to bond surfaces for a CLT panel composed of southern pine lumber and polyurethane adhesive. Evaluation of the CLT panels used the five-point bending test for bending stiffness, bending strength and shear stiffness in addition to measuring the resistance to shear by compression loading. The shear strength and percent wood failure values obtained from the resistance to shear by compression loading. The optimal combination of manufacturing parameters studied was 100% press pressure and a press time of 80% of the manufacturer recommendations. The addition of water to the bondline surfaces was deemed unnecessary for CLT materials conforming to the PRG-320 standard. Comparison of mechanical properties with Grade V3 showed higher bending strength and shear stiffness values.
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 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 the ANSI/APA PRG-320 product standard. Bending strength, bending stiffness, shear strength, resistance to shear by compression loading strength, and resistance to delamination were measured according to ANSI/APA PRG-320, and test results were compared to the V3 grade values. 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 V3 grade, while resistance to delamination did not meet the established criteria. The resistance to delamination results may have been effected 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 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.