Rolling shear strength is one of the key design parameters for point-supported cross-laminated timber (CLT) flat-slab system where the panels are directly supported by columns without any beams. The specified rolling shear strength of CLT in the current Canadian design standard could be conservative estimates considering the variability in wood species, stress grade, thickness of lamellas, layups and grain orientations. To address these gaps in knowledge for the North American market, a Post + Plank research project is being undertaken by Fast+Epp structural engineers in collaborations with the University of Northern British Columbia. In the first phase of the project, presented herein, CLT rolling shear strength under in-plane shear loading was evaluated. A total of 330 specimens (11 series with 30 replicate each, sized 100 mm (width) × 300 mm (length) were tested. The parameters varied were thickness: 3-ply of 89 mm and 105 mm, and 5-ply of 139 mm and 175mm with multiple species and fabricators, and both visual and machine stress graded CLT. The mode of failure was crack development along the growth ring. The results show that the mean rolling shear strength of various Canadian CLT species was between 0.94 MPa to 1.8 MPa. Although thin layers exhibited relatively higher rolling shear strength, these differences were found not to be statistically significant.
