Testing and modeling of CLT-to-CLT joints made using hardwood dowels and screws with varying spacing

• Published in: Construction & building materials 2025-01, Vol.458, Article 139449
• Main Authors: Vilguts, Aivars, Phillips, Adam R., Antonopoulos, Chrissi, Griechen, Darrin
• Format: Article
• Language: English
• Subjects: Cross-laminated timber; Hardwood dowels; Mass timber; Self-tapping screws; Single-shear connection; Timber connections; Timber materials; Wooden dowels
• ISSN: 0950-0618
• DOI: 10.1016/j.conbuildmat.2024.139449

With the increasing popularity of mass timber, utilizing large-diameter wood screws and hardwood dowels can offer an easy and cost-efficient way to join structural elements. However, the existing research on hardwood dowels is limited to single fastener joints under monotonic loading. No research is available on the group effects of joints with multiple hardwood dowels. This paper presents the results of 96 monotonic and cyclic single-shear plane CLT-to-CLT joint tests with hardwood dowels (Red Oak and Yellow Birch, 25.4 mm diameter) and self-tapping wood screws (8 mm diameter) in Grand-Fir CLT, where screws were inserted both perpendicular and at a 45-degree angle to the grain for comparison to hardwood dowels. The study evaluated the mechanical properties of the joints by changing fastener spacing. Mechanical properties such as yielding and peak strength, displacement, elastic and yielding stiffness, and ductility were evaluated. The results showed equal strength and stiffness properties for hardwood dowels comparable with large-diameter screws. Additionally, the hardwood dowel joints demonstrated moderate ductility properties. The strength and stiffness of the tested joints were compared with analytical equations found in the literature by considering the group action factor of the fasteners. Lastly, a nonlinear force-displacement model was presented and compared to the experimental results and analytical calculations, which gives the possibility to predict and optimize the mechanical behavior of hardwood dowel and screw joints with varying numbers and spacing between fasteners. •Experimental and analytical analysis of 96 single shear-plane CLT-to-CLT joints with hardwood dowels and screws.•The strength and stiffness of hardwood dowels are comparable to those of large-diameter screws.•Hardwood dowel and screw joints demonstrated moderate and high ductility properties.•A nonlinear force-displacement model developed to predict and optimize joints' mechanical behavior.