Timber connections are crucial because they function to connect the timber elements together as a structural system. In large-scale timber structures, the structural elements are usually connected by means of steel plates and dowels. We believe that birch plywood could be a potential alternative to the traditional steel plates since the connection with wood-based structural plates is more environmentally friendly, with less prefabrication demand and the ease of on-site installation.
When employing birch plywood as connection plates, there are mainly two types of connections could be developed, namely, mechanical connection and adhesively bonded connection. Compared to mechanical connection, adhesively bonded connection holds the benefits of being cheaper, stiffer, and stronger. However, fundamental knowledge regarding the surface-to-surface bonding technique and bonding performance, particularly in terms of the hybrid bonding between different engineered wood products
(plywood and glulam) and different species (birch and spruce), is vital but currently in lack of research, which raises my interests on this topic.
Additionally, the quality of the bond line is sensitive to the surrounding environment (temperature and relative humidity) during assembly. Gluing on-site is thus not recommended. Instead, it is preferred to do the gluing in the factory and then transport the assembled structure to the construction site. Despite this highly prefabricated approach, the size of the timber structures is often limited by the transportation capacities, such as the length and height of the transporting vehicle.
For long-span timber structures that cannot be entirely transported to the site, we came up with a new connection system with adhesive application in the factory and adhesive-free assembly on the site. Specifically, the workflow of the proposed system consists of: (1) adhesively bonding separate birch plywood plates to each timber element in the factory; (2) transporting these prefabricated packages to the construction site; and (3) assembling them together with an adhesive-free technique by means of steel rods.
We conducted laboratory tests on a timber frame corner to investigate the structural behaviours of the proposed connection system. We found that this system can hold about 70-80% of the load that a fully bonded joint can handle, also with noticeably enhanced ductility. We will present the geometrical illustration of the proposed connection system and more details on the test results in the extended abstract.
Keywords: innovative timber connection, adhesively bonded connection, on-site adhesive-free assembly, birch plywood, ductility
Authors
Tianxiang Wang
Division of Building Materials, Department of Civil and Architectural Engineering, KTH Royal Institute of Technology, Sweden
Yue Wang
Division of Building Materials, Department of Civil and Architectural Engineering, KTH Royal Institute of Technology, Sweden
Mattia Debertolis
Division of Building Materials, Department of Civil and Architectural Engineering, KTH Royal Institute of Technology, Sweden
Roberto Crocetti
Division of Building Materials, Department of Civil and Architectural Engineering, KTH Royal Institute of Technology, Sweden
Magnus Wålinder
Division of Building Materials, Department of Civil and Architectural Engineering, KTH Royal Institute of Technology, Sweden
Login to download the PDF