Lateral and Withdrawal Capacity of Fasteners on Hybrid Cross-Laminated Timber Panels

Abstract

Cross-laminated timber (CLT) is an orthogonally laminated timber panel product made using dimensional lumber. It is gaining traction in the construction industry, as is evident by the increasing number projects using CLT. Currently, CLT panels are manufactured using single species of wood; however, as the product matures, several combinations of species/grades layups may be used to optimize the properties and achieve economic efficiency. The panels using these different combinations of species and grades are called hybrid CLT. For successful integration as a new panel layup in the CLT market, the performance of different connections using the hybrid layup of panels needs to be evaluated. Because hybrid CLT panels can possibly use materials of different densities into which the fasteners embed, fastener performance needs to be characterized according to the existing density profile. A series of laboratory tests are performed to obtain the performance of two different fastener types (a screw and a nail) on seven different layups to provide quantitative information about the performance of single fasteners used for common connection system. Additionally, the existing analytical models for predicting fastener performance under loading are adjusted to account for potential density profiles in hybrid CLT panel applications, and the results are compared to experimental results. Marked effects of face-layer density on the performance of the fasteners under lateral and withdrawal loading are captured. Neither yield mode nor the strengths of the fasteners are affected significantly. Results suggest that the adjusted models can be used to account for the effect of varying density.