Grant: Alliance Grants

The advent of large and tall mass timber structures over the last 10-20 years is a result of innovations in both product and connection development. One of these innovations is self-tapping screws (STS) that tap the timber material as they are driven in. It is not an understatement to say that without the availability of STS, the use of mass timber products would still be largely limited to small structures. The Canadian standard for Engineering Design in Wood, CSA O86, includes provisions for the design of connections with STS for the first time in the 2024 edition of the standard. These provisions will provide designers with more confidence in specifying STS. Due to their ease of on-site installation and high withdrawal resistance, STS are an excellent fastener to reinforce timber members to enhance their load-bearing resistances in a number of applications, including: i) connections with dowel-type fasteners (loaded perpendicular and parallel to the wood grain as well as moment connections); ii) timber beams with end notches, openings and engineered beam hanger connections; iii) bearing details including point-supported cross-laminated timber panels. To facilitate the wider use of the above applications of self-tapping screws, standardized design procedures are necessary, so that engineers can properly design the reinforcement details instead of adapting empirical approaches. This research project will generate empirical data on tested connections and components, both reinforced and unreinforced, and material strength data input for the analytical models. These models will form the basis of design methods to be implemented in the 2029 edition of CSA O86.