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Shrinkage cracks are some of the most common defects in timber structures obtained from woods with an uneven distribution of moisture content and are subject to external dynamic environmental changes. To accurately predict the changes in the moisture content of wood components at any time and position, this study first applied the principles of food drying and established a moisture field model for laminated wood based on the analogy between heat and humidity transfer. A model for predicting the moisture content of wood that considers time and spatial distribution was then proposed. Second, by collecting relevant experimental data and establishing a finite element analysis model, three moisture absorption conditions (0–9.95%, 0–13.65%, and 0–17.91%) and four desorption conditions (34–5.5%, 28–8.3%, 31–11.8%, and 25.5–15.9%) were analyzed. In the moisture absorption comparison, the time needed to reach 95% equilibrium moisture content was 2.43 days, 4.07 days, and 6.32 days. The rate at which the internal components reached equilibrium moisture content exceeded 10 days. The temporal and spatial distribution of wood moisture content revealed the correctness of the proposed wood moisture field model. Finally, the moisture content prediction model was applied in the order of characteristic equation solutions, moisture content gradient difference, and laminated wood size. The results revealed that the established humidity field model can predict the wood moisture content and how it changes over time and in space. Notably, 1–2 orders for the solution of the characteristic equation are recommended when applying the prediction model. The greater the difference in moisture content, the faster the equilibrium moisture content is reached. The moisture content varies greatly based on the component size and position. Notably, the influence of moisture gradient and wood size on the average wood moisture content cannot be ignored.

This work investigates the influence of ISO 834 temperature-time and heat release rate (HRR)-time fire curves on compartments featuring inert or exposed cross-laminated timber (CLT) ceilings. A series of tests was performed in a scaled compartment, aiming to investigate the observed effects on the temperature distribution, heat flux values and the overall fire behaviour. Under the standard ISO 834 temperature-time curve, the CLT-equipped compartment required 55% less fuel to replicate temperature profiles compared to an inert configuration, reflecting the timber’s contribution to fuel load. In contrast, when an HRR-time curve was used, an 80% increase in HRR for the CLT-equipped compartment was observed, due to sustained combustion of the exposed timber; also, HRR-based testing elevated compartment temperatures by 20% on average, with transient deviations exceeding 80% during early fire stages. The results underscore the limitations of temperature-time curves, which impose fixed thermal profiles and neglect fuel contributions from combustible materials, potentially underestimating fire risks, thus highlighting the need for fire testing methodologies that incorporate HRR as a key parameter when assessing the fire performance of combustible construction materials.

Timber has become known to be a sustainable alternative building material. Engineered wood products such as glulam and cross-laminated timber provide suitable structural performance, however, they present challenges regarding their reusability, recyclability, health, and broader environmental impact due to the use of adhesive to connect the layers. This research explores alternative mechanical connection systems of X-shaped hardwood shear connectors and micro-notches to join timber layers, eliminating the need for adhesives or metal fasteners. A series of 40 push-out tests with 10 different configurations are carried out to evaluate the stiffness and load-bearing capacity of each method. The variables under investigation include lamella thickness, inclusion of micro-notches between layers, grain direction of the shear connector, distance between the connectors, alignment or shifting of the position of two rows of shear connectors, presence of conical cuts, and three different heights of X-shaped connector. The results are analyzed to determine the optimal shear connection configuration for enhanced structural performance of the mechanically connected timber beams.

Timber structures are vulnerable during the cooling phase of a fire, especially in compression, a factor not currently addressed by design methods based on standard fire exposure. This paper presents an experimental investigation on the thermal and mechanical performance of encapsulated cross-laminated timber (CLT) elements during and after standard fire heating. Data from two reduced-scale furnace tests on CLT specimens, encapsulated with either one or two layers of fire-rated plasterboard, were used to evaluate the reduction in compression and bending capacity. The effective cross-section and bending capacities were determined using the Reduced Cross-Section Method (RCSM) and an Advanced Calculation Method (ACM), both provided in the current and proposed versions of Eurocode 5. The most significant capacity reductions were predicted for the cooling phase when using the ACM, where the bending capacity dropped below 45% of the original capacity for both cases. In the RCSM, the capacity fell below 85% for both samples when using the current Eurocode 5 and below 67% for both samples when using the revised Eurocode 5. These results show the inadequacy of simplified methods based on standard fire exposure to predict the capacity of timber elements in the cooling phase of a fire.

Mass timber products can reduce greenhouse gas emissions by replacing steel and cement. However, the increase in wood demand raises wood prices, and the environmental consequences of these market changes are unclear. Here we investigate the global carbon and land use impacts of adopting mass timber products, focusing on cross-laminated timber as a case study. Our results show that higher wood prices reduce the production of traditional wood products but expand productive forestland by 30.7–36.5 million hectares from 2020 to 2100 and lead to more intensive forest management. If the cumulative global cross-laminated timber production reaches 3.6 to 9.6 billion m 3 by 2100, long-term carbon storage can increase by 20.3–25.2 GtCO 2 e, primarily in forests (16.1–17.7 GtCO 2 e) and in cross-laminated timber panels (4.1–8.1 GtCO 2 e). Including emission reductions from steel, cement, and traditional wood products, the net reduction of life-cycle greenhouse gas emissions will be 25.6–39.0 GtCO 2 e. This study reveals that global adoption of mass timber products can expand forestland, increase carbon stocks in forest and wood products, and decrease life-cycle greenhouse gas emissions.

To reduce the carbon impact of new buildings, wood is seeing increased use as a structural material. Cross-laminated timber (CLT) and glue-laminated wood (glulam) elements allow the construction of multi-storey buildings. However, wood is vulnerable to moisture, especially when naked wood is exposed to weather during the construction process. This paper presents the moisture strategy employed during the construction of a four-storey CLT/glulam building in Trondheim, Norway. The building was constructed without the use of a weather-protective tent, requiring alternative protective measures. The construction of the main structure was scheduled to be as short as possible. Local protective measures were employed to protect the structure from rain and free water was removed after rain events. The project was closely supervised by the client, with particular care for moisture control. Moisture was regularly measured at 50 points throughout the building. No wooden surfaces were encapsulated until a wood moisture content below 15 weight-% was measured. The performance of the moisture strategy was evaluated using measurements of wood moisture, indoor climate, airtightness, and visual inspections. The wood moisture content quickly decreased as the building envelope was assembled, indicating that drying was well facilitated. In the first year after construction, gaps between the flooring and baseboards were observed, suggesting that the wooden elements have experienced some shrinkage. The moisture safety strategy is deemed to have been generally successful. The overall experiences were important in the development of new recommendations in the SINTEF Building Research Design Guides for CLT structures.

As timber is combustible, the inherent fuel load of a mass or engineered timber structure can significantly impact compartment fire dynamics compared to a non-combustible structure. Recently, large-scale open-plan testing reaffirmed these phenomena in compartments with exposed timber, with a rapid transition to fully developed fire following the ignition of the exposed timber ceiling. However, no standardised approaches have been developed to investigate this phenomenon at a bench-scale inverted (i.e. downward-facing) orientation. A method to study the ignition of inverted combustible surfaces is proposed whereby the Fire Propagation Apparatus (FPA) is modified to permit testing at this inverted orientation. Results for this comparative piloted ignition study for a conventional horizontal orientation and an inverted orientation indicate proof of the applicability of the methodology whereby the times to ignition of Cross-Laminated Timber (CLT) were higher for the inverted orientation, compared to a horizontal orientation, demonstrating the suitability of the methodology.

European beech is one of the dominating wood species in central Europe and the most abundant hardwood species in Austrian, German and Swiss forests. Today, it is predominantly used for the provision of energy and in the furniture industry. With the increasing demand on forests to provide sustainable raw materials for energy as well as products, the importance of lesser-used wood species like European beech has continuously increased over the last decade. The application in load-bearing products has gained significant interest. In order to connect the current and historical state of knowledge about this wood species, this review provides an overview of the past and present utilization of European beech wood. On the basis of the historical literature, technical approvals and standards of established products, it aims to summarize the extensive state of the art of this wood species and provide an overview of recent scientific publications in the field of wood material science. Based on the reviewed literature, current research efforts deal with different engineered wood products like glued laminated timber, cross-laminated timber and laminated veneer lumber. Furthermore, strength grading, adhesive technology as well as improving dimensional stability is of particular interest.

This paper presents how procedures of building design can be improved by integrating trustable structural knowledge. Such a procedure allows closing the gap between as-designed building behavior and as-built building behavior and is particularly crucial for innovative structures where extensive engineering expertise may be lacking. By leveraging validated engineering principles and data-driven insights, the proposed methodology ensures more reliable and predictable design outcomes. The framework emphasizes the importance of transparent building behavior, allowing continuous monitoring and iterative refinement for designers. It also highlights how evidence-based decision-making may enhance structural performance. The capacities of this approach are demonstrated through a real-world application, specifically by improving the vibration serviceability of tall structures made of cross laminated timber (CLT) panels. This is achieved by utilizing modal property measurements from two case study buildings and applying a generalized updating procedure to refine the scaling factor for the elastic moduli, adjusting the manufacturer’s assessed values of the CLT panels.

There is an increased interest in using Cross-laminated timber (CLT) in construction, but many buildings are erected without weather protection, which poses a risk of moisture impact if wood is exposed to precipitation during construction. The construction industry argues that there are no documented critical moisture levels for CLT and no specific test method. In the study, a laboratory test set-up was developed to study mould growth under realistic and controlled climatic conditions after exposure to distilled water and spore suspension. In the experiments, small test specimens of CLT structures were exposed to distilled water for 1 day or 1 week. During the development of the method it was found that exposed for one day and then given the opportunity for open drying did not give rise to mould growth. On the other hand, growth occurred on surfaces that could not dry immediately, for example at connection points. For specimens exposed for one week, mould growth arose regardless of whether the surfaces could dry immediately or not. The conclusions apply primarily to the climates studied. The methodology needs to be further developed, with other scenarios being studied, and calibrated against samples exposed to outdoor air, dust, dirt and rainwater.