Search Results (200)

Cross-laminated timber (CLT) is increasingly used in multi-story timber construction, but its combustible nature requires reliable fire protection, particularly in layered wall assemblies with concealed cavities. This study compares two medium-scale cross-laminated timber (CLT) sandwich wall assemblies exposed to radiant heat flux of 20 kW/m² for 90 min: an uncoated reference assembly and an assembly with PROMADUR^® intumescent coating applied to the CLT surfaces. Both specimens consisted of a 90 mm three-ply CLT panel encapsulated with 12.5 mm gypsum-fiber boards fixed to a wooden stud frame forming a 40 mm installation cavity. Fire-test observations were supplemented by simultaneous thermal analysis (STA), i.e., thermogravimetry (TG)/differential thermogravimetry (DTG)/differential scanning calorimetry (DSC), of uncoated and coated CLT specimens under oxidative conditions. During the applied medium-scale radiant exposure, the unexposed-face temperatures of both assemblies remained below the insulation temperature-rise limits defined in STN EN 1363-1; however, these limits were used only as a comparative benchmark and the test does not represent a formal fire-resistance classification. The coated assembly showed improved thermal protection during the early and intermediate stages of exposure, delaying a critical thermal event near the wooden stud by approximately 35 min. However, flaming combustion of the stud occurred at about 75 min and led to degradation of the intumescent char within the cavity. In contrast, the uncoated assembly reached higher early CLT surface temperatures but showed no flaming combustion during the test. STA results supported the fire-test interpretation: the coated specimen showed a 37% reduction in peak DTG rate, a higher residual mass at the end of the test, and substantially greater mass loss in the 150–280 °C range, consistent with intumescent activation and volatile release. The results indicate that, under the tested medium-scale exposure, the intumescent coating improved early and intermediate thermal protection of the CLT surface, but did not prevent late-stage cavity flaming involving the wooden stud. Therefore, the behavior of intumescent-coated CLT in partially enclosed cavities with combustible framing should be validated under replicated, standardized and larger-scale fire exposure. Full article

Point-supported connections are an innovative modern connection design that can benefit from the 2-way structural action of cross-laminated timber (CLT) slabs, which is typically not considered in traditional timber design. It also allows for flatter ceiling surfaces where no beams are needed to support the mass timber floor slabs. In an attempt to better understand the structural behaviour of this type of connection in fire conditions, preliminary unloaded fire tests were conducted to evaluate their thermal performance. The test results indicated that, for these tested configurations, the presence of steel connection components does not inherently increase charring rates within adjacent mass timber elements. While the outcomes provided valuable insights on the thermal performance of such assemblies, their actual mechanical behaviour under structural loading in fire conditions remains unknown. This paper presents the results of two structural fire-resistance tests under load: Test 1 had the gap fully exposed to fire, and Test 2 had the gap protected by a firestop. Neither assembly reached failure during the 2 h of standard fire exposure, while the target load could not be fully maintained to the end of the tests. Test 1 experienced charring at the CLT-steel plate interface, while Test 2 did not. Their mechanical behaviours were also similar. Lastly, a preliminary design approach is being proposed, although it requires further validation. Full article

Cross-laminated timber (CLT) is recognized as a leading engineered wood product because of its sustainability, reduced carbon footprint, and growing application in civil engineering structures. However, the numerical modeling of CLT systems is challenging due to numerous connection details and the lack of standardized models. This study evaluates the effect of different types of experimental data on the finite element model (FEM) updating process for CLT panels. To this end, 30 CLT panels with varying configurations were subjected to monotonic loading to characterize their load–displacement responses, and ambient vibration tests were conducted to identify their dynamic characteristics. Initial FEMs of the CLT panels were developed and then updated using three different approaches: displacement-based, frequency-based, and a combined method. The results indicated that updating based solely on displacement data accurately captures static responses but fails to adequately represent modal behavior. In contrast, frequency-based updating yielded reliable natural frequencies but resulted in significant discrepancies in displacement predictions. The combined updating method provided consistent results, reducing displacement differences to 0–14.29% with an average of 3.23%, while maintaining frequency discrepancies below 5%. Overall, the results show that obtaining a reliable numerical model of CLT systems requires combining different types of experimental data. Full article

Cross-laminated timber (CLT), an engineered timber product with distinctive features, has significantly broadened the applicability of timber structures. The self-tapping screws (STSs) with excellent anchorage performance have become one of the primary connectors used in CLT structures. However, the long-term withdrawal resistance is susceptible to environmental factors such as temperature and humidity fluctuations, which may lead to reduced CLT density and corrosion-induced degradation of the steel components. These effects represent a critical life-cycle challenge to the structural integrity and safety of timber connections. This study aims to investigate the withdrawal resistance of STSs in CLT under material aging effects. To achieve this, a two-step experimental program was designed. First, the effects of two artificial accelerated aging methods (ASTM D1037 and improved version of ASTM D1037) on the withdrawal resistance of STSs in glued laminated timber (glulam) were compared to validate the feasibility of the improved protocol. This comparison was necessary to ensure that the improved protocol produces a degradation pattern without altering the failure mechanism. Subsequently, a series of CLT specimens with embedded STSs were subjected to 0, 3 and 6 aging cycles to investigate the withdrawal behavior including aging characterization, failure modes, load–displacement curves, withdrawal capacity, and stiffness. The results indicate that the failure mode of CLT joint with STSs under the improved aging scheme was the consistent pull-out of STSs, identical to that observed in the glulam, confirming mechanistic consistency. After three and six aging cycles, the normalized withdrawal capacity retention rates were 104.98% and 95.36%, respectively. The stiffness is more significantly affected by aging. The corresponding normalized stiffness retention rates were 85.60% and 80.94%, respectively. As the number of aging cycles increased, the occurrence of wood fiber tearing became more pronounced and the ratio of the corresponding load to the peak load decreased. Furthermore, ensuring adequate distance from the vertical glue layer was found to lead to greater long-term resilience and withdrawal capacity. Full article

Dowel-laminated timber (DLT) is a composite structural material manufactured entirely from wood. Increasing awareness of the sustainability, end-of-life recyclability, and potential health concerns associated with synthetic adhesives used in cross-laminated timber (CLT) and glulam has intensified industry and academic interest in adhesive-free mass-timber systems like DLT. In Australia, however, DLT remains under-researched. This paper addresses global and local knowledge gaps by developing a linear-elastic numerical modelling method for DLT using Australian finite element analysis software Strand7 and investigating structural optimisation strategies, including the use of Australian hardwoods. A finite element model captured the characteristic response of a DLT beam from the University of Liverpool within the linear-elastic range. Reduced dowel spacing, alteration of lamella thicknesses and targeted dowel placement in the shear zones increased global stiffness in the parametrisation study. Incorporating Australian hardwood in the outer lamellae further improved bending performance. Structural viability in the Australian context was indicated through the design of a project-scale DLT beam prototype assessed to relevant Australian Standards. The modelling approach and findings are presented alongside a discussion of behavioural nuances, contributing to the growing body of research on DLT. Full article

The post-tensioned cross-laminated timber (CLT) rocking wall is a recently developed resilient CLT lateral force-resisting system with a self-centering feature. The structural responses of the systems with different designs need to be determined and evaluated efficiently to promote the development and standardization of industrial applications. This study developed a computationally efficient, component-assembled numerical model for post-tensioned cross-laminated timber (PT CLT) rocking walls that captures decompression, post-tension self-centering, and energy dissipation within a framework. The single wall model was assembled using nonlinear zero-length springs for the compression at the CLT bottom, truss bar element for the PT tendon, and elastic shell element for the CLT panel deformation. The energy dissipation device, the UFP, was modeled with nonlinear one-dimensional springs between the wall panels in the coupled wall model. The wall models were separately calibrated considering the wall designs of single-panel walls and coupled walls. Both single and coupled wall models predicted the initial stiffness, decompression, yielding, post-yield stiffness, and reloading/unloading stiffness. The residual drift and nonlinear unloading captured with the PT model were also validated with the test data. A two-story platform structure model was established based on the NHERI Tallwood project, assembled with the coupled wall model and CLT slab in shell elements and columns in Euler beam elements. With recorded ground acceleration signals from the test, the platform structure’s peak story displacement and inter-story drift were simulated with less than 30% differences for most cases. Unlike existing detailed contact-based models, the proposed approach balances local damage fidelity and computational efficiency. The validated model provides a framework for evaluating PT CLT wall design parameters considering their influence on full structures. Full article

The construction sector’s drive for sustainability has increased the use of Cross-Laminated Timber (CLT), yet its structural reliability is governed by the integrity of the adhesive bond line. This study evaluates the influence of three one-component polyurethane (PUR) formulations (R1, R2, R3) on the adhesion performance of maritime pine CLT. To isolate adhesive-related effects, lamellas were mechanically classified by modulus of elasticity (MOE) and randomly allocated within stiffness classes. Adhesive characterization through ABES, FTIR, and DSC revealed that R3 exhibited slower cure kinetics (t₀ = 5482 s) but higher thermal stability. Mechanical testing showed that all formulations developed structurally effective dry bonds with shear strengths exceeding 7.1 MPa, with R3 achieving significantly higher dry shear and interlaminar strength. However, 24 h water immersion caused a catastrophic strength reduction exceeding 95% across all formulations, shifting the failure mode from the wood substrate to the adhesive layer. DSC analysis identified glass transition temperatures between 28 °C and 32 °C, which are consistent with the potential for moisture-induced plasticization near service temperatures. These results indicate that while slower-curing formulations like R3 enhance bond quality in dense softwoods due to improved interphase formation, all evaluated PUR systems showed significant vulnerability to saturated conditions, suggesting that adequate moisture protection is essential for maritime pine CLT applications. Full article

Cross-Laminated Timber (CLT) has gained increasing attention as sustainable and efficient material for slab systems in construction. However, the lack of standardized design guidelines and comprehensive performance comparisons between different CLT-based slab solutions limits its widespread application, particularly in emerging markets with limited local expertise. This study aims to fill this gap by evaluating the structural performance and applicability of four CLT slab systems: (i) CLT slabs, (ii) CLT–concrete composite slabs, (iii) CLT–glued-laminated timber (GLT) beam ribbed slabs, and (iv) CLT–steel beam composite slabs. A comprehensive design methodology based on the Gamma method and Eurocode 5 is developed, critically applied, and its limitations discussed for each system, considering both ultimate and serviceability limit states, with special attention to vibration criteria and shear connection efficiency. The systems are compared in terms of maximum span, self-weight, thickness, and dynamic response under residential and office load categories. Results show that ribbed slab systems with timber or steel beams achieve the longest spans (up to 14 m for residential use), with lower self-weight, while CLT and CLT–concrete slabs exhibit maximum spans of 9 m with reduced thickness. Serviceability limit states, particularly vibration, were identified as the governing design constraints in most cases. This study provides a systematic comparison of CLT slab solutions, contributes to the development of reliable design tools, and identifies priorities for experimental validation, supporting the broader adoption of CLT in regions with growing timber construction sectors, such as Portugal. Full article

Screw withdrawal force is a key mechanical property related to the load-bearing capacity and reliability of mechanically fastened timber structures. This study investigates the screw withdrawal performance of cross-laminated timber (CLT) manufactured from spruce, beech, and poplar, including both homogeneous and hybrid layups. The selected species represent materials with different densities and regional availability in Hungary. A one-component polyurethane adhesive was used for panel manufacturing. Screw withdrawal force was determined using two methods: a universal testing machine (UTM) and a manual portable device (MPD). The highest withdrawal forces were observed in beech-based configurations, while the lowest values were measured for spruce. Poplar-based configurations demonstrated intermediate but competitive performance, exceeding the reference spruce values. Statistical evaluation confirmed a significant effect of layup configuration on withdrawal resistance. The MPD measurements were on average approximately 9% higher than UTM results, indicating a consistent and quantifiable inter-method difference. The results demonstrate that hybrid CLT configurations can be optimized by combining species of different densities and that portable testing methods provide reliable estimates of withdrawal performance. These findings contribute to the understanding of connection behavior in hybrid CLT and support the practical application of semi-destructive testing methods for in-situ assessment. Full article

This study presents a data-driven and explainable artificial intelligence (XAI) framework for quantitatively analyzing research trends in the seismic performance of timber structures. Unlike conventional bibliometric approaches based on descriptive statistics, the framework integrates large-scale literature mining, natural language processing, topic modeling, network analysis, and SHAP-based machine learning to enable structural and temporal interpretation. A dataset of 248 journal articles from OpenAlex was processed through a unified pipeline, including domain-specific filtering, text preprocessing, and temporal balancing. Topic modeling identified eight research themes spanning traditional component-level mechanics and emerging areas such as cross-laminated timber (CLT), hybrid systems, and performance-based design. Network analysis revealed a highly interconnected structure centered on key concepts such as shear walls, connections, stiffness, and cyclic behavior. SHAP-based analysis further showed that research evolution follows a layered and cumulative pattern rather than simple topic replacement: classical themes remain foundational, while newer concepts such as CLT and structural capacity have become increasingly influential. The proposed framework provides a reproducible and scalable method for quantitatively mapping research structures and temporal dynamics in timber seismic engineering. Full article

Glued-laminated timber (GLT) and cross-laminated timber (CLT) panels are increasingly used as exposed structural elements in representative buildings. These structures are often part of public-use areas, which require the application of restrictive fire-safety measures without significantly affecting the color of exposed wooden surfaces during the service life of these building elements. The effect of fire-retardant treatments on the color of Scots pine (Pinus sylvestris L.) wood was evaluated using five impregnation agents with different active substances. Changes in gloss and color characteristics—lightness (L*), green-red coordinate (a*), and blue-and-yellow coordinate (b*)—were measured sequentially directly after impregnation, after exposure to variable humidity conditions and after exposure to UV radiation. The total color difference (ΔE*) ranged from 2.82 to 17.76 after impregnation and increased to 6.31–20.71 after aging, indicating a risk of aesthetic deterioration of fire-retardant-treated wood surfaces under typical service conditions for timber structures in representative buildings. The most pronounced color changes were observed for the fire retardant containing potassium and copper compounds (FR4) and the combination of 2-aminoethanol with boric acid (FR5). Full article

This work proposes a design-oriented numerical modelling approach for predicting the seismic response of multi-storey Cross-Laminated Timber (CLT) buildings. The model is based on a phenomenological approach and is capable of accurately replicating the seismic behaviour of multi-storey CLT wall systems by means of a properly calibrated equivalent wall stiffness, taking into account both connections and panel deformability. An extensive set of multi-parametric linear analyses is performed to calibrate the wall equivalent stiffness by varying significant design parameters such as: CLT wall geometry, connection pattern, seismic mass and level of seismic intensity. An ad hoc iterative procedure is developed in order to calibrate the wall equivalent stiffness in terms of significant design parameters (e.g., principal elastic period, internal forces in the connection elements and inter-storey drifts). The aim of the procedure was to minimise the error between the results obtained with the proposed phenomenological model and those obtained with refined numerical models. The latter were designed to accurately reproduce the actual response of the CLT systems analysed. The results of the multi-parametric analyses are discussed and summarised in a design abacus that allows a direct implementation of the proposed phenomenological model and, therefore, a simple and efficient seismic analysis for CLT buildings. Full article

Because of concentrated connection damage, the impact of sequential hazards on CLT shear wall systems is much more severe than that on traditional concrete and steel structures considering ductile component behaviors. The present paper evaluated the dynamic response of CLT wall structures in wind-only and sequential seismic–wind scenarios and compared the structural dynamic responses and damage levels of different CLT wall systems. The structural models were established separately based on an SOM benchmark structure, a SOFIE project three-story CLT shear wall structure, and a PT CLT wall platform structure from the NHERI Tall Wood project. The equivalent fluctuating wind load was calculated with the ASCE 7 average wind speed, the reference ESDU wind profile, calibrated wind pressure distribution, and simulated fluctuation from the NatHaz Online Wind Simulator. The sequential load was applied to the structural models in the order of seismic excitation, resting time, and then dynamic wind load. The dynamic responses of different CLT wall structures were compared among loading scenarios with increasing seismic and wind intensities. The wind-excited peak story displacement and acceleration for both CLT structures were significantly magnified in the sequential seismic–wind scenarios compared with the wind-only scenarios. The simulation results indicated that the sequential seismic–wind scenarios caused significant acceleration in damaged connections for the conventional CLT shear wall structure. The PT CLT wall structure had minor displacement and acceleration, which were linear to the wind loading factors. For the conventional CLT shear wall structure, the magnification of the acceleration was found to have a strong correlation with the natural frequencies of the damaged structure. This study demonstrated that the wind responses of the PT wall structures were in a safe range after the seismic event, and conventional CLT wall structures need to be re-evaluated under sequential scenarios for structural resilience assessment. Full article

Mass timber elements such as glued laminated timber (Glulam) and cross-laminated timber (CLT) have become increasingly prominent in sustainable construction due to their structural efficiency and reduced environmental impact. However, fire performance remains a critical consideration for structural safety. This paper presents a comparative assessment of experimentally measured and code-predicted fire performance parameters for Glulam and CLT, including charring rate, effective charring depth, zero-strength layer (ZSL) thickness, and residual mechanical properties. The evaluation covers major international fire design standards: Eurocode 5 (EC5), the Australian Standard (AS/NZS 1720.4), the Swedish Handbook (Swedish), American Wood Council (AWC TR10), and the Canadian Standard (CSA O86). Across all Glulam datasets, charring rate predictions agreed with tests within approximately ±20%, while AS/NZS 1720.4 consistently over predicted charring and effective char depth by around 40%. In contrast, CLT demonstrates greater variability, primarily due to adhesive degradation, delamination, and lamella orientation, which influence heat transfer and post-fire capacity. CLT data exhibited higher scatter, with effective charring depth showing standard deviations of approximately 30 to 40%, ZSL thickness averaging about 2.5 times the typical 7 mm assumption, and residual stiffness commonly reducing to around 20 to 25% of initial values after standard fire exposure. Overall, findings suggest that current standards adequately address Glulam performance but require refinement to capture the complex fire response of CLT. Continued experimental research and targeted code development, particularly within the Australian Standard, are essential to improve reliability and confidence in performance-based fire design for mass timber structures. Full article

The increasing use of engineered timber in modern architecture raises critical concerns about fire safety, particularly when combustible linings are exposed within compartments. Classical compartment fire framework, largely derived from non-combustible enclosures, may not adequately capture the dynamics introduced by materials such as cross-laminated timber (CLT). This study investigates how combustible linings influence the fluid dynamic fields of compartment fires derived from the thermal field using CFD simulations informed by experimental data. A series of configurations, from inert to fully lined compartments, were analysed to isolate the effect of burning boundaries. Results show a progressive intensification of fire conditions with additional combustible surfaces: upper-layer temperatures approach 900 °C, smoke layers thicken, and stratification becomes more pronounced. Velocity fields are similarly affected, with peak inflow and outflow velocities doubling compared to the inert case and new vortical structures emerging near burning walls. These findings highlight that exposed CLT significantly amplifies radiative and convective heat feedback, modifying both temperature distributions and flow patterns in ways not captured by the traditional framework based on the inverse opening factor. This underscores the need for performance-based fire design approaches integrating both thermal and fluid dynamic perspectives, ensuring safe implementation of timber in modern construction. Full article