Can notched CLT panels be reinforced with fully threaded screws?

Tension-site notches can result in excessive tensile stresses acting perpendicular to the grain of the panel.
Fully threaded screws can be installed to prevent splitting of notched wood members. This reinforcing application is backed by numerous studies and approved for ASSY VG Fully-Threaded Self-Tapping Screws in the approval ETA 11-0190. However, in the case of CLT notch reinforcement, a definitive mechanical model has not been developed yet for this specific application, however notched CLT panels can certainly be reinforced with fully-threaded ASSY screws. Three key points need to be addressed in order to do this.

The mechanical model used to calculate splitting stresses assumes that the wood member is under unidirectional bending. More importantly, it assumes a parabolic shear stress distribution along the cross-section of the member based on Beam Theory. Due to anisotropic behaviour, lamellas will experience different shear stresses depending on their orientation (rolling shear).

Crack formation and propagation in the crossing layers at the notch corner, and the influence of sliding shear fracture, to our knowledge, has not been investigated for CLT.

Lamellas are typically glued on the wide face and not the narrow face. This means that crack propagation can follow gaps in the panels rather than the grain direction.
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Relevant Technical Resources

Gallery perpendicular grain reinforcement cover Design for Reinforcement of Perpendicular to Grain Connection
Gallery notch reinforcement usa cover Notch Reinforcement Design USA
Gallery tall wood webinar Webinar: Structural Screw Technology in Tall Wood Buildings
Gallery webinar2 cover Webinar: Reinforcing Wood with Full Thread Screws

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