Experimental investigation on the effect of accelerated ageing conditions on the pull-out capacity of compressed wood and hardwood dowel type fasteners

• Published in: Holzforschung Vol. 76; no. 1; pp. 89 - 98
• Main Authors: Mehra, Sameer, Harte, Annette M., Sotayo, Adeayo, Guan, Zhongwei, O’Ceallaigh, Conan
• Format: Journal Article
• Language: English
• Published: Berlin De Gruyter 27.01.2022; Walter de Gruyter GmbH
• Subjects: accelerated ageing; Accelerated aging tests; Adhesives; Aging; Climatic conditions; compressed wood; Connectors; Densification; dowel type connections; Dowels; End of life; Fabrication; Fasteners; Friction; Hardwoods; Laminates; mass timber; Mechanical properties; Pull out tests; pull-out capacity; Recovery; Shape effects; shape-recovery; Substitutes; Substrates; Timber; Timber (structural); Timber construction; Wood
• ISSN: 0018-3830; 1437-434X
• DOI: 10.1515/hf-2021-0097

The widespread use of adhesives in timber construction has negative implications for the end-of-life disposal or re-use of the structural timber components. To promote the circular bioeconomy, it is preferable to substitute adhesives with more sustainable alternatives such as wood-based connectors. Today, robotic fabrication technologies facilitate the development of dowel-laminated timber (DLT) products whereby hardwood dowels are used to connect timber laminates as a substitute to adhesives. In recent years, thermo-mechanical densification of wood has resulted in significant improvements in the mechanical performance of the wood. This modified product often termed compressed wood (CW) has a shape-recovery effect which may be beneficial for the development of DLT products and timber-timber connections with improved friction fit with time. To test the hypothesis, accelerated ageing tests were carried out on CW-timber and hardwood-timber dowel type connections subjected to variable climate conditions. Finally, the capacity of the connections or friction fit was assessed using pull-out tests. Results show that the shape-recovery effect leads to the continuous expansion of the CW dowels and facilitates a friction fit with the timber substrate yielding higher pull-out loads when compared to hardwood dowels.