• White Papers
  • May 18, 2023

Withdrawal Resistances of ASSY Screws at Various Angles to the Grain

Discover the secret to accurately calculating withdrawal resistance in mass timber connections with MTC’s ASSY self-tapping screws (STS). Our comprehensive technical paper delves into the theory, reduction factors, and practical guidance for calculating withdrawal resistance in STS installations. Design engineers often encounter uncertainties surrounding the use of the end-grain adjustment factor, Ceg, and angle-to-grain reduction factor, Rα. Addressing this lack of clarity, our paper provides valuable insights on applying both factors in end-grain applications, including Glulam beams, columns, and CLT panels.

One common question from engineers is whether both reduction and adjustment factors should be applied. Our paper clarifies that both Ceg and Rα factors are crucial in ensuring accurate withdrawal resistance calculations. While the NDS-2018 Ceg factor covers parallel and perpendicular-to-grain applications, it falls short when STS are installed at varying angles to the grain. To bridge this gap, MTC Solutions’ Structural Screw Catalog offers the angle-to-grain reduction factor Rα, designed to address withdrawal applications across a full range of values from 0° to 90°.

Here you’ll find practical examples that showcase the application of adjustment and reduction factors, which can help when interpreting code provisions intended for lag screws in the design of STS connections in withdrawal.

With MTC Solutions’ white paper, enhance your understanding and application of these two factors, the justification of their use, and their implications for the strength and durability of connections in Glulam and CLT.

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