Nos talents en construction bois au cœur des discussions lors de la 2e NextGen Wood Conference 2025!

Plusieurs membres de notre centre ont pris part à la 2e édition de la NextGen Wood Conference, qui s’est tenue à Ottawa du 26 au 28 mai 2025. Cet événement d’envergure a réuni chercheurs, professionnels de l’industrie et décideurs afin d’échanger sur les avancées en construction bois et les innovations dans le domaine des assemblages structurels.

Le professeur Alexander Salenikovich a joué un rôle central dans l’organisation du « Timber Connections Workshop » du 28 mai, en collaboration avec le professeur Thomas Tannert (University of Northern British Columbia). Cet atelier spécialisé a réuni une cinquantaine de participants venus de divers horizons – chercheurs universitaires, ingénieurs praticiens, représentants de l’industrie et étudiants aux cycles supérieurs – pour discuter des avancées les plus récentes en matière d’assemblages pour les structures en bois massif et en bois lamellé-croisé. L’événement a permis de faire le point sur les tendances actuelles en matière de conception, de performance mécanique et de sécurité des assemblages, tout en offrant une plateforme d’échange entre la recherche et la pratique. Le professeur Christian Dagenais, a également pris la parole à titre de conférencier. Il a présenté ses recherches sur la performance au feu des connexions modernes en bois massif, suscitant un grand intérêt chez les participants. Sa présentation a contribué à alimenter les discussions sur les enjeux normatifs et les défis de la conception sécuritaire en contexte de changement climatique.

Plusieurs membres de notre communauté étudiante ont activement contribué aux différentes activités de la NextGen Wood Conference 2025, illustrant la vitalité et l’engagement de la relève en construction bois.

• Antony Beaulieu, Luc Girompaire et Rosalie Côté ont donné des conférences, permettant d’échanger avec les professionnels lors des sessions techniques, du réseautage et des débats sur les enjeux actuels de la construction bois.

• Kiavash Gholamizoj a donné une conférence et présenté une affiche scientifique lors du Timber Connections Workshop. Ses travaux, portant sur les essais cycliques d’assemblages en bois lamellé-collé à l’aide de goujons et de plaques en acier, ont suscité l’intérêt des spécialistes en génie structural désireux d’optimiser la performance sismique des bâtiments en bois.
• Félix Coulaud a assisté à la fois à la conférence et à l’atelier, bénéficiant d’une vision complète des défis et avancées dans le domaine.
• De leur côté, Christopher Gagnon et Coralie Offroy ont activement participé au Timber Connections Workshop, approfondissant leurs connaissances sur les approches innovantes en matière d’assemblages structuraux et de matériaux hybrides, notamment à travers les démonstrations expérimentales et les discussions techniques.

Cette participation a renforcé les liens entre la recherche universitaire et l’industrie, et a permis à nos membres de s’affirmer comme des acteurs engagés dans la réflexion sur le développement durable en construction bois.

Nous remercions chaleureusement les organisateurs et tous les participants pour cette occasion unique de collaboration et d’échanges inspirants.

Quelques présentations marquantes :

• Fire Performance of Modern Mass Timber Connections
  Par Christian Dagenais et Monireh Aram
  Cette présentation portait sur les défis liés à la performance au feu des assemblages modernes en bois massif, en soulignant les lacunes des normes actuelles canadiennes et en présentant des résultats préliminaires d’un projet de recherche de 5 ans mené en collaboration avec FPInnovations et le Ministère des ressources naturelles et de la faune du Québec.

• Brittle Failure of CLT Connections with Inclined STS
  Par Amir Einipour, Alexander Salenikovich, Jianhui Zhou et Thomas Tannert
  Cette étude a exploré les modes de rupture fragile dans les assemblages CLT avec vis autotaraudeuses inclinées, révélant des comportements plus complexes que ceux prévus par la norme CSA O86 et proposant une nouvelle approche prédictive.

• Cyclic Tests on Glulam Timber Connections with Dowels and Slotted-in Steel Plates
  Par Kiavash Gholamizoj et collaborateurs
  Des tests expérimentaux ont été menés pour évaluer la résistance, la ductilité et les modes de rupture des assemblages à goujons renforcées par des plaques en acier, en vue d’améliorer leur conception dans les structures à contreventement en bois lamellé-collé.

• Stiffness of Timber Connections with Dowel-type Fasteners
  Par Tao Gui, Ying Hei Chui et Alexander Salenikovich
  Ce travail a comparé plusieurs modèles théoriques pour prédire la raideur des assemblages à goujons, essentiel pour assurer le bon comportement structurel des systèmes en bois.

• Impact of Forestry Practices on the Carbon Footprint of Lumber Products
  Par Rosalie Côté, Évelyne Thiffault et Ben Amor
  Cette recherche a quantifié l’influence des pratiques forestières sur le bilan carbone biogénique du bois d’œuvre, un aspect crucial pour mieux intégrer les flux de CO2 biogénique dans les analyses de cycle de vie des produits du bois.

Détails:

Session « Timber connections Workshop»

Fire Performance of Modern Mass Timber Connections (présentation orale)- Christian Dagenais, Monireh Aram
Mass timber buildings are becoming popular worldwide, with their environmental benefits becoming ever more important as the effects of climate change becoming increasingly apparent. One of the challenges of building timber structures is evaluating and properly designing for its performance in fire, with the connections between timber elements typically being seen as critical components of the structure. Recent studies have largely focused on evaluating the fire performance of connections using bolts and dowels. These types of connection can be challenging to design and are usually found in “Heavy Timber Construction” (Type IV in the US). They are not quite found in recently constructed timber structures in North America. Modern mass timber connections have seen little research attention regarding their fire performance. Modern concealed connections include, among others, proprietary connectors made of cold-formed steel, milled or extruded aluminum, as well as knife plates and bearing plates made of custom steel. In Canada, very little information is given in Annex B of CSA O86 [1] related to fire-resistance of timber connections. It essentially only requires that all metallic components should be located within the effective cross-section, thus providing some level of thermal cover. It however lacks at providing guidance on gap tolerances between the elements, char penetration (if any) and performance criteria. When designing for the American market, fire design of connections is given in the Fire Design Specification (FDS) for Wood Construction [2] and Technical Report 10 [3], both published by the American Wood Council. Guidance is given with respect to char penetration at unbonded intersections (joints), thermal separation time and maximum temperature rise criteria. When the gap between elements is greater than 3.2 mm (1/8”) and air flow through the gap is not prevented, it is assumed that the joint is fully exposed to fire. Given the conservatism of the US provisions, a few design teams, mass timber manufacturers and connectors’ suppliers conducted fire-resistance tests so that code-compliant solutions could be made available to the design community. While these tests provided code-compliant solutions to achieve from 1-hr to 2-hrs fire-resistance rating, most of them used fire stop sealant and large beams to provide sufficient wood cover to the metallic components. This result in solutions that are likely overdesigned and no longer cost-competitive against other types of construction since sustainable materials are typically more effective on cost and more sustainable by wasting less material. There is a need to develop design provisions based on first principles and applicable to modern mass timber connections, for ultimately implementing into the next edition of CSA O86. This presentation will present preliminary results of a 5-years research project led by FPInnovations in collaboration with industry partners and Ministère des ressources naturelles et de la faune du Québec. Main observations will be presented along with potential recommendations for future work. The work done is also complimentary to the CWCRN Theme 2-2A projects on connections.

Cyclic tests on glulam timber connections with dowels and slotted-in steel plates (affiche)- Kiavash Gholamizoj , Alexander Salenikovich , Ying Hei Chui , David Hanna

Modern mass timber braced frames rely on ductile connections to dissipate energy effectively. However, brittle failure modes in dowel-type connections may occur before the fasteners yield, limiting ductility and energy dissipation capacity. This study addresses these challenges by conducting experimental cyclic tests on dowel connections with one or two slotted-in steel plates. Connections were designed per CSA O86 [1] and Eurocode 5 draft [2] and tested to evaluate stiffness, resistance, ductility, energy dissipation, and failure modes, as well as to compare the two design approaches.
The tested connections form part of glulam brace elements in multi-storey timber braced frames. Each joint includes 12.7 mm (1/2-in.) dowels in various configurations at one end, while the opposite end, features steel side plates with inclined self-tapping screws, overdesigned to allow for reuse across tests (Figure 1). A total of 72 tests were conducted across nine series: five configurations with single slotted-in plates and four with double plates, using 6 or 12 dowels in various spacings (Figure 2). Each series included two static tests and six one-directional cyclic tests in axial tension. The static tests are used to determine the cyclic displacement protocols based on ISO 16670 [3]. Performance parameters, derived from load-slip graphs, highlight the effects of fastener spacing and end distance on resistance and failure modes. Experimental results are compared with predictions from CSA O86 and Eurocode 5, providing insights for designing reliable connections that meet the high force demands of mass timber braced frames.

Brittle failure of clt connections with inclined STS  (présentation orale)- Amir Einipour , Alexander Salenikovich , Jianhui Zhou , Thomas Tannert

The crosswise layup in ross-laminated timber (CLT) panels leads to distinct brittle failure modes compared to those observed in solid timber or glulam. CLT connections with self-tapping screws (STS) installed at an inclined angle, may fail under brittle failure modes for which the guidance in the 2024 edition of the Canadian Standard for Engineering Design in Wood (CSA O86) is limited. In a recent study at the UNBC Wood Innovation Research Lab, the brittle failure modes and load-carrying capacities of CLT connections with inclined STS were investigated, see Figure 1a. A total of 18 series with six two-sided with STS connections installed at a 45º angle were tested under uniaxial tension, encompassing a range of connection layouts that considered CLT lay-up, screw penetration length, edge distance of the connection, and screw arrangements.
All connections exhibited quasi-linear behaviour up to the maximum load and failed in a brittle manner. The observed brittle failure modes across different test series were more complex than those outlined in CSA O86, including occurrences of rolling shear and layer separation alongside the predominant plug shear, see Figure 1b. Using screws of the same length in CLT with different layups affected the load-carrying capacity due to changes in the failure plane. Connections near the panel edge showed lower capacity than those in the centre, highlighting the impact of edge distance on brittle failure. Based on these findings, a new approach for predicting brittle failure in CLT connections with inclined STS will be proposed.

Session « NextGen Wood Conference »

Characterizing char rate of wood under real-fire scenarios- Antony Beaulieu

The use of engineered wood in construction is increasing in popularity due to its numerous advantages. However, its combustible nature remains a significant constraint in building construction to comply with fire safety requirements provided in building codes. The existing common design methods for wood structural elements rely on a normalized time-temperature curve from CAN/ULC S-101 (Standard Methods of Fire Endurance Tests of Building Construction Materials). However, this curve does not accurately reflect real fire scenarios, as it assumes a continuously increasing temperature over time, whereas in reality, the temperature eventually decreases. This project aims to characterize the charring rate of wood exposed to real fire conditions by analyzing important factors that influence this rate, such as heat flux and oxygen concentration. The goal is to provide performance-based design data to improve knowledge of the behaviour of the charring rate of wood exposed to different parameters. To obtain these data, experimental tests will be carried out using a controlled atmosphere cone calorimeter device to evaluate various parameters and a propane furnace to simulate real fire time-temperature curves. The collected data will be compared to assess the impact of different factors on the charring rate of wood and will be used to propose a charring rate equation for real-fire scenarios in design applications. This research will help characterize the charring rate of wood to propose design data that better represents a real fire scenario in buildings.

Stiffness of timber connections with dowel-type fasteners- Tao Gui , Ying Hei Chui , Alexander Salenikovich

When designing structural timber systems, serviceability limit states (SLS) can govern the final design solutions. Deformations in mechanical timber connections play a key role in controlling common SLS, such as vibration and deflection, which are dependent on the stiffness of the connections. It is also required for ultimate limit states (ULS) design. For instance, in statically indeterminate structures where the applied design load is resisted simultaneously by more than one component, and the load distribution is governed by stiffness properties of these components. Therefore, accurate models predicting the deformation or stiffness of timber connections are required for design purposes. Early timber connection models were largely based on the theory of beam on elastic foundation (Winkler foundation). Winkler foundation model works reasonably well for strength prediction but not stiffness. This is because the Winkler theory tends to lead to an over-estimation of the deformation due to the assumption of decoupling of the foundation springs. An improved approach is necessary for connection stiffness prediction. This paper investigates the use of Multi-spring foundation  and Half-space foundation  theories to address the limitations of Winkler foundation model. Finite element models based on the three different foundation theories were developed and the predicted results are compared. It was found that the Multi-spring foundation and Half-space foundation theories provide more accurate predictions of connection stiffness for dowel-type fasteners compared to the Winkler foundation theory. However, further experimental studies are required to determine the specific application ranges of these models.

Cyclic tests on glulam timber connections with dowels and slotted-in steel plates – Kiavash Gholamizoj , Alexander Salenikovich , Ying Hei Chui , David Hanna

Modern mass timber braced frames rely on ductile connections to dissipate energy effectively. However, brittle failure modes in dowel-type connections may occur before the fasteners yield, limiting ductility and energy dissipation capacity. This study addresses these challenges by conducting experimental cyclic tests on dowel connections with one or two slotted-in steel plates. Connections were designed per CSA O86 and Eurocode 5 draft  and tested to evaluate stiffness, resistance, ductility, energy dissipation, and failure modes, as well as to compare the two design approaches.
The tested connections form part of glulam brace elements in multi-storey timber braced frames. Each joint includes 12.7 mm (1/2-in.) dowels in various configurations at one end, while the opposite end, features steel side plates with inclined self-tapping screws, overdesigned to allow for reuse across tests (Figure 1). A total of 72 tests were conducted across nine series: five configurations with single slotted-in plates and four with double plates, using 6 or 12 dowels in various spacings. Each series included two static tests and six one-directional cyclic tests in axial tension. The static tests are used to determine the cyclic displacement protocols based on ISO 16670. Performance parameters, derived from load-slip graphs, highlight the effects of fastener spacing and end distance on resistance and failure modes. Experimental results are compared with predictions from CSA O86 and Eurocode 5, providing insights for designing reliable connections that meet the high force demands of mass timber braced frames.

Fire performance of modern connections in mass timber construction- Luc Girompaire, Christian Dagenais, Alexander Salenikovich

The fire performance of mass timber connections is influenced by multiple factors extensively documented in the literature, including structural load ratio, type of fastener, diameter and number. Another critical factor is the gap size between connected elements, which can significantly affect the fire performance by increasing temperatures within joints and accelerating fastener heating. Like other construction materials such as steel and aluminium, timber experiences a reduction in mechanical properties as temperature rises. Gap size also impacts the charring rate. Both U.S. and European  standards introduced a gap factor that locally increases the charring rate of timber at joints. In European standards, a gap between 2 mm and 5 mm increases the charring rate by 20% , while in U.S. standards, gaps exceeding 3.2 mm (1/8”) are considered fully exposed to fire. Currently, Canadian standards do not account for gap size in charring rate adjustments. Therefore, further investigation is needed to assess its impact and establish clear guidelines for Canadian designers. This study aims to quantify the effect of gap size between two timber members exposed to the CAN/ULC S101 time-temperature curve on heat flux and the charring propagation within the joint. Additionally, the influence of wood grain orientation on charring rate will be examined. To this end, four joint configurations (shown in Figure 1) and four gap sizes will be tested. In the first test series, the lateral sides of the specimens will be encapsulated to ensure unidirectional charring propagation. A second test series will investigate tri-directional charring propagation.

Impact of Forestry Practices on the Carbon Footprint of Lumber Products- Rosalie Côté, Évelyne Thiffault, Ben Amor

Forest management influences the carbon balance of the forest ecosystem. Thus, forestry practices influence the biogenic carbon footprint of harvested timber. However, in current life cycle assessments for building timber, biogenic CO2 fluxes are not systematically considered. The aim of this research was to quantify the effect of forest management parameters on the biogenic carbon balance of a m3 of timber from the eastern boreal forest. Using forest management compartment units of the boreal balsam fir forest of Quebec as case studies, we created forest management scenarios that included variations in four parameters: harvest type, i.e., the proportion of clearcut vs. partial cut harvesting, harvest intensity in % area harvested yearly, harvest rotation age and proportion of harvested lumber destined to sawmilling vs. destined to other wood products. We then simulated scenarios over a 150-year period in CBM-CFS3 for the ecosystem dynamics and MoSiR for the product end-of-life to obtain average biogenic CO2 fluxes per m3 of lumber, with positive flux values indicating net carbon emissions to the atmosphere, and negative values indicating net ecosystem carbon sequestration. Our results suggest linear or non-linear relationships for each of the four parameters tested. Simulations enabled us to find threshold points for harvest type and intensity where the carbon balance becomes negative, i.e. where the m3 of lumber generates net sequestration of biogenic CO2. Quantifying the effect of forest management will enable us to improve our practices to achieve carbon neutrality, and also to better include biogenic carbon accounting in life-cycle analyses.

Pour en savoir plus sur la 2e édition de la NextGen Wood Conference & Workshop 2025 ! Cliquez ici 

Par : Besma Bouslimi

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