Adhesive-and Metal-Free Assembly Techniques for Prefabricated Multi-Layer Engineered Wood Products: A Review on Wooden Connectors

Abstract

Engineered wood products (EWPs) are being increasingly used as construction materials. EWPs are currently being made using synthetic adhesives or metal fasteners, which lead to poor recyclability and reusability. Therefore, this review paper focused on emerging adhesive- and metal-free assembling techniques including wood dowels, rotary-dowel welding, wooden nails, and dovetail joining as alternative ways of making prefabricated EWPs. This will contribute towards green construction and optimising the building process to minimise its negative impact on the environment and its inhabitants, while maximising the positive aspects of the finished structure. The respective advantages and shortcomings will be compared with those of equivalent EWPs. In general, the dowel-laminated timber (DLT) provides sufficient load-bearing capacity and even better ductility than EWPs of equivalent size, but its relatively low stiffness under a bending load limits its application as a structural element. Optimised manufacturing parameters such as dowel species, dowel spacing, dowel diameter, dowel insertion angle, dowel shape, etc. could be studied to improve the stiffness. The improved mechanical properties and tight fitting due to set-recovery of densified wood support its use as sustainable alternatives to hardwood dowels in DLT to overcome problems such as the loosening of connections over time and dimensional instability. The rotary welding technology could also enhance the strength and long-term performance of dowel-type joints, but its poor water resistance needs further investigation. The main obstacles to implementing DLT products in the market are missing technical information and design guidelines based on national codes.

Views of Cross-Laminated Timber (CLT) Manufacturer Representatives around the World on CLT Practices and Its Future Outlook

“…It is also worth noting that while adhesive bonding and metal fasteners are acknowledged for their reliability and demonstrated long-term efficacy [44,45], there exists a requirement for a more environmentally friendly alternative in joining timber components within multi-layer wooden beams and panels [46,47]. In recent times, various adhesive-free methods for connecting multi-layer beams and panels have been introduced [48]. These techniques encompass the following: (1) joining multi-layer timber with wooden dowels [49] (such as untreated hardwood dowels [50], thermo-hydro-mechanical densified wooden dowels [51], and rotary-welded wooden dowels [52]); (2) dowel-laminated timber (DLT) [53]; (3) wooden nails [54]; (4) dovetailed panels [55,56]; and (5) linear wood-welding technology [57].…”

An Experimental Comparison of Airborne Sound Insulation between Dovetail Massive Wooden Board and Cross-Laminated Timber Elements

“…This fabrication technique presents an alternative to traditional CLTs by eliminating the release of harmful substances from adhesives [17]. Given the novelty of this approach, comprehensive information pertaining to its technical and structural performance remains limited, warranting further research into specific domains such as dimensional and structural stability [18]. As part of the DoMWoB project (Dovetailed Massive Wood Board Elements for Multi-Story Buildings) (refer to Acknowledgment), endeavors encompassing sound insulation were undertaken.…”

Evaluating Fire Performance: An Experimental Comparison of Dovetail Massive Wooden Board Elements and Cross-Laminated Timber

“…Adhesives and metal connectors are commonly employed in EWPs to replace conventional timber-to-timber joints in modern wooden structures [10]. In this regard, adhesive bonding holds significant importance and serves a crucial role in EWPs [11].…”