Block tear-out resistance of CLT panels with single large-diameter connectors

Novel solutions with large-diameter connectors for cross-laminated timber (CLT) assemblies require wood brittle failure to be avoided through capacity-design-based provisions to protect the CLT panels. Current design standards, such as the Canadian Standard for Engineering Design in Wood (CSA-O86), do not cover the block tear-out resistance of CLT panels associated with large-diameter connectors. The primary objective of the research presented herein was to assess the block tear-out and net-section tension resistances of CLT panels loaded in plane and to provide guidance for the required end distances of single large-diameter connectors such as internal-bearing hold-downs. A total of 117 full-scale CLT specimens were tested to determine their in-plane tear-out resistance. 3-ply and 5-ply CLT panels with different loaded end and the edge distances and varying the grain direction of the outer layers were tested under quasi-static monotonic loading. The results demonstrate that brittle block tear-out or net-section tension failure can occur in CLT panels. These failure modes have to be accounted for in design. A simple stress-based strength criterion considering the rolling shear strength of wood delivers conservative and reasonably accurate predictions of the CLT brittle resistance.