Group Effects for Shear Connections with Self-Tapping Screws in CLT
Publication: Journal of Structural Engineering
Volume 145, Issue 8
Abstract
Cross-laminated timber (CLT) panels, when used as shear walls or diaphragms, are commonly connected with multiple () dowel-type fasteners in a row. For such connections, it is frequently observed that the load-carrying capacity of multiple fasteners is less than the sum of the individual fastener capacities, a phenomenon referred to as the group effect. The research presented in this paper investigated the group effect in self-tapping screw (STS) shear connections between CLT panels. Different joint types (surface splines with STS in shear, and half-lap and butt joints with STS in either shear or withdrawal) were evaluated in a total of 175 quasi-static monotonic and reversed cyclic tests, with the number of STS in one row varied between 2 and 32. The results showed that the group effect for the joint capacity (strength) can be expressed as for all joints under static loading, where is the effective number of fasteners. In case of cyclic loading, a more pronounced group effect was observed that can be expressed as . These reductions are significantly less conservative than the current Canadian design provisions for lag screws. For the reduction in stiffness and ductility, and can be used for all joints under static and cyclic loading, respectively. Finally, the capacity, ductility, and stiffness for joints under cyclic loading where the STS acted in withdrawal were on average 10% lower compared with the static values.
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Acknowledgments
This research was supported by MITCAS Canada through an Accelerate project with My-Ti-Con Timber Connectors, Canada. The support by SWG-Schraubenwerk Gaisbach Germany, Structurlam Products, and the help of the technicians at the University of British Columbia is much appreciated. The analytical work was supported by the British Columbia Innovation Council through funding to the BC Leadership Chair in Tall Wood and Hybrid Structures Engineering.
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©2019 American Society of Civil Engineers.
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Received: Jul 26, 2018
Accepted: Dec 17, 2018
Published online: May 17, 2019
Published in print: Aug 1, 2019
Discussion open until: Oct 17, 2019
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