Glulam Research Articles

Enhancing fire performance of glulam beams through thermal treatment, inorganic impregnation, and densification techniques

The present research investigates a novel, environmentally benign modification method for improving the fire performance of Chinese fir that grows quickly and at low density. This wood is known for its susceptibility to burning and rapid loss of load-bearing capacity in fires. After thermal treatment, inorganic impregnation, and densification, Chinese fir was utilized as the fire-exposure surface for glulam beams. Three sides of full-size members were subjected to fire tests lasting 60 and 90 minutes. Considering the gluelines' thermal conductivity, the improved glulam beams' fire performance was thoroughly evaluated using the finite element program ABAQUS. The study found that the composite modification approach enhanced the weight percentage and mass density of the wood laminates by 32.53 % and 67.87 %, respectively. After 60 min of fire exposure, the charring rates on the exposed surface of the members with the modified laminates were 13.5 % and 27.8 % lower than those of standard glulam beams, indicating a considerable improvement in fire resistance. Greater post-fire residual cross-sectional area and improved fire resistance performance were correlated with an increase in the quantity of modified laminates. The composite modified glulam beams showed a noticeable temperature gradient, which was explained by higher density and specific heat capacity and consequently improved overall fire resistance, according to finite element analysis. The corner effect on the glulam beam cross-section became more evident with prolonged heating, while the gluelines had minimal impact on overall heat transfer.

Study on bending performance of prefabricated glulam-cross laminated timber composite floor

Abstract The glulam-cross laminated timber (CLT) composite floor is a type of prefabricated composite floor that integrates glulam beams and CLT slab into a unified structure using shear connectors. To investigate the bending performance of the glulam-CLT composite floor, the bending test was conducted on a full-scale composite floor under static load. The study comprehensively analyzed the failure mechanism, load–deflection behavior, interface slip and strain distribution of the glulam-CLT composite floor. The test results of the composite floor indicated that the failure mode was tensile fracture of the wood beam at the bottom. As the load increased, the deflection deformation of the mid-span beam exceeded that of the edge beam. When the load reached its ultimate limit, the deflection deformation of the mid-span beam increased by 14.4% compared to the edge beam. In the early loading phase, the strain distribution of the composite section satisfied the assumption of a plane section. However, the strain distribution deviated from this assumption with the increased load due to the relative slips between the glulam beam and CLT flange. To calculate the bending performance of the composite floor, the M-shaped section of the glulam-CLT composite floor was simplified as T-section composite beams. The linear-elastic method for determining the flexural rigidity and ultimate bearing capacity of the glulam-CLT composite floors was proved to be accurate and reliable. The findings provided valuable insights into the bending behavior of the CLT flange under load and emphasized the non-uniform stress distribution caused by shear lag effects.

Cold temperature effects on the impact behaviour of glued-laminated timber beams

Engineered wood products, such as glued-laminated timber (glulam), have been and are continuously being utilized in the construction of tall timber buildings and notable landmark bridges. This infrastructure, particularly the latter, may be exposed to hazardous impact loads throughout their service life. As little research has been conducted on the impact behaviour of glulam beams under cold temperature conditions, there is a need to investigate the potential effects of impact loading on glulam structural elements at cold temperatures. This paper presents an experimental investigation aimed at understanding the effects of cold temperatures on the impact behaviour of glulam timber beams. Fifteen glulam beams were tested under quasi-static and impact loading, under ambient and cold temperatures. Drop weight impact testing was performed to simulate dynamic loading conditions similar to those experienced in real-world scenarios. The results indicate that both the loading regime and cold temperatures have a significant influence on the strength and stiffness of glulam beams, whereby statistically significant increases in the moduli of rupture and elasticity were observed, however, no interaction between the two variables occurred. A single-degree-of-freedom (SDOF) model was developed and validated using the experimental test results and found to provide good accuracy.

A Review of Cradle-to-Gate Greenhouse Gas Emission Factors for Canada’s Harvested Wood Products

Abstract With the previous decade’s (2010 through 2019) greenhouse gas emissions remaining the highest on record, focus on emissions mitigation efforts is paramount. Harvested wood products (HWPs) can store carbon for various timespans depending on the product and its end uses. Life cycle inventories (LCIs) are the base for life cycle analyses (LCAs), as they represent a comprehensive catalogue of the raw data essential to complete an LCA. However, most LCI documentation is in the form of case studies of different types of HWPs, with varying LCI results that reflect varied system boundaries, case-specific conditions, and assumptions. Our goal was to conduct a systematic literature review to evaluate, analyze, and synthesize previously reported Canadian HWP data and to initiate a Canadian database based on reported cradle-to-gate HWP emission factors. HWPs were categorized as lumber, traditional structural panels, mass timber, nonstructural panels, and wood pellets. Based on our analysis, we found that softwood lumber produced the lowest cradle-to-gate emission factor (61.99 kg of CO2 equivalent [CO2eq] per m3 HWP) while I-joists produced the highest (218.55 kg of CO2eq per m3 HWP). Resource extraction emissions accounted for most of the overall emissions for softwood lumber, oriented strand board, cross-laminated timber, and glue-laminated timber. Meanwhile, manufacturing accounted for most of the emissions for plywood, I-joists, cellulosic fiberboard, particleboard, and wood pellets. Substantial gaps exist in published LCI data and, when possible, publishing detailed LCI data is encouraged to support additional HWP life cycle analyses.

Identification of Modal Properties of a Tall Glue-Laminated Timber Frame Building under Long-Term Ambient Vibrations and Forced Vibrations

Identification of Modal Properties of a Tall Glue-Laminated Timber Frame Building under Long-Term Ambient Vibrations and Forced Vibrations

FLEXURAL STRENGTHENING OF THERMALLY MODIFIED RUBBERWOOD GLULAM BEAMS WITH FRP UNDER STATIC AND CYCLIC LOADS

The purpose of this research is to investigate the flexural properties and cyclic response of strengthened with fiber reinforced polymer (FRP) of glulam beam made from thermally modified rubberwood. The efficiency of three different FRP was assessed based on the bonding properties. The experimental results demonstrated that the glass fiber-reinforced polymer (GFRP) showed the strongest adhesion. Static and cyclic flexural tests were also carried out to study the behavior of glulam beams. The static test results indicated that double sides strengthened glulam beam enhanced their flexural strength. The strengthened glulam beams under static load demonstrated a reduced deformation rate due to increased modulus of rupture compared to non-strengthening glulam beam. The cyclic load test showed the strengthening effect on improving energy dissipation and ductility, while the impairment of strength did not affect.

Deformation level and specimen geometry in compression perpendicular to the grain of solid timber, GLT and CLT timber products

Compression Perpendicular to Grain (CPG) is a crucial aspect of timber design, particularly with the advent of engineering wood products like Cross Laminated Timber (CLT), often used in point-supported structures. After many years of discussion, the mechanics-based model by Van der Put has finally been included in the new Eurocode draft. This model offers a more systematic approach to design with a solid theoretical foundation for stress dispersion. However, there is still a need for improvement, especially in two areas: accounting for the capacity increment associated with increasing levels of deformation and determining the maximum effective height to be assumed in calculating the load spreading in deep timber elements. In this paper, the authors focus on these two areas of improvement for GLT, solid timber and CLT timber products. They analyse the data of two extensive experimental campaigns conducted at Norsk Treteknisk Institutt (Norwegian Institute of Wood Technology) and at the Norwegian University of Science and Technology (NTNU) on Glued Laminated Timber (GLT), Solid Timber (ST) and CLT. Additionally, they validated a parametric finite element (FE) model in Abaqus to assess the effect of the height of the timber element on stress distribution. A parametric approach developed in Abaqus aims to find the optimal height threshold to be assumed in the new code formulation.

Mass Timber Beams Under Loading

This summer, I participated in a few research projects under the supervision of Dr. Woods, focusing on the load-bearing performance of mass timber structures. The projects aim to address critical gaps in understanding timber beam-column connections under loading to enhance structural safety and promote the use of sustainable building materials. I assisted in the construction and instrumentation of experimental test specimen setup (including retrofit beams from a decommissioned bridge, CLT-Steel composite beams, and curved glulam beams), executing the tests, and analyzing the resulting data. Advanced sensors like digital image correlation and distributed fiber optic sensors provided insights into the behaviour of beams. Through hands-on training in the Structures Laboratory and support in data analysis using MATLAB, I gained a deep understanding of experimental testing under loading and contributed to a collaborative effort in structural engineering.

Theoretical and experimental studies on the bending properties of glued laminated timber manufactured with Chinese fir

China has been increasingly promoting the use of prefabricated timber structure buildings in recent years. However, unlike other countries, China lacks a diverse range of local tree species and engineered wood products suitable for load-bearing components in timber structures. This shortage poses a risk to the sustainable development of timber structures in China. This issue is addressed in this study, which focuses on the development and manufacture of glued laminated timber (GLT) using Chinese fir from plantation forests. The dynamic elastic modulus of 549 laminae was evaluated using the FAKOPP stress wave approach. A total of 28 laminae were randomly selected from Classes I, II, and III to assess the influence of stress grading on bending performance. This study included an analysis of failure modes, bending capacity, and the prediction model for bending stiffness of GLT with different layups and cross-sectional heights. The findings showed that the dynamic elastic modulus of the laminae followed a normal distribution. The bending strength and modulus of elasticity of finger-jointed laminae across different grades were 29.59 MPa to 37.05 MPa and 8.13 GPa to 10.94 GPa, respectively. The mechanical properties of both same-grade and mixed-grade composition GLT manufactured from Chinese fir met the TCT28 (MOR≥28 MPa, MOE≥8000 MPa) and TCYD24 (MOR ≥ 24 MPa, MOE ≥ 8000 MPa) garde requirements in GB/T26889, respectively. Failure modes in the GLT specimens typically began at the knots or finger joints of the bottom layer laminae. The cross-sectional height had no significant effect on the modulus of elasticity of GLT but exerted a significant effect on bending strength. The prediction model for bending stiffness, developed using the transformed section method, agreed with the experimental results. The outcome of this research provides a scientific and data-driven foundation for the application of Chinese fir in the field of structural materials.

Environmental potentials from wood cascading: A future-oriented consequential yet dynamic approach considering market and time-dependent biogenic carbon effects for selected scenarios under German conditions

As sustainable forestry limits the roundwood supply, wood cascading emerges as a promising concept to meet the growing demand resulting from Germany's transition to a bioeconomy. To assess the environmental impacts of wood cascading resulting from shifting the incineration of recovered wood and the associated substitution of future energy mixes and materials, a consequential life cycle assessment (CLCA) of a wood cascading system providing glued-laminated timber (GLT), particleboard, heat, and electricity is conducted. The assessment of environmental consequences requires a holistic approach, including future-oriented German energy and market scenarios. Furthermore, to analyze the impact of biogenic carbon dynamics, this CLCA was coupled with a dynamic life cycle assessment (DLCA) considering forest growth scenarios and temporal aspects. The results indicate a strong influence of market shifts related to material substitution, followed by energy substitution on the environmental impacts of wood cascading. In fact, the results endorse the implementation of the concept of high-quality wood cascading for substituting non-wood products in Germany, as a transformational path towards a bioeconomy and the achievement of net greenhouse gas neutrality. Compared to the effects of the material and energy substitution scenarios, the forest growth scenarios, which focus on tree species composition influenced by future temperature change and CO2 concentration scenarios, only show a minor influence on global warming impacts. As the findings from applying DLCA contrast with the static approach, it emphasizes the importance of a time-differentiated analysis of biogenic carbon in the evaluation of wood cascading.

Timber-timber composite (TTC) joints made of short-supply chain beech: Push-out tests of inclined screw connectors

This paper presents the results of experimental investigations on six-layered, homogeneous glulam beams made of Italian short supply chain beech (Fagus sylvatica L.). At first, the beams were produced and mechanically characterized for bending, then, they were employed to realize timber-timber composite joints and tested under quasi-static monotonic loading. The test configurations were adopted to reproduce connections used in timber-to-timber composite structures for applications in new constructions. Outcomes in terms of connection stiffness, strength, static ductility and failure modes are presented and discussed. Moreover, the experimental stiffness were used to carry out analytical verification at the serviceability and ultimate limit states to extend the validity of the proposed screw and specimen’s configurations.

Performance of ANN, Random Forest and XGBoost methods in predicting the flexural properties of wood beams reinforced with carbon-FRP

ABSTRACT Wooden material can be used in different areas due to its various positive properties. Glued Laminated wooden elements (glulam) are wood composite materials widely used especially in the construction industry. Carbon fiber-reinforced polymers (FRP) are widely used to increase the bearing capacity values of glulam beams and improve their overall load-displacement behavior. This study was carried out in two stages. In the first stage, the bending properties of glulam timbers of different sizes with wide spans reinforced with carbon fiber-reinforced polymers were experimentally examined. In the next stage, the obtained data were predicted with three different machine learning techniques (ANN, Random Forest and XGBoost). As a result of the study, it was determined that as the section dimensions increased, the bending properties increased, and the reinforcement was effective by approximately 22%. All three different prediction techniques used could make predictions with high accuracy. However, it was determined that the best prediction was made with Random Forest (R2: 0.9892). Therefore, the bending properties of reinforced beams of different sizes can be predicted with machine learning (ML) techniques.

Experimental Analysis of Bonding in Steel Glued into Pine Timber.

Combining steel with wood has been practised for many years. The issue is related to two main areas, i.e., bonding steel elements with wood so that they serve as connectors facilitating the assembly of wood elements and bonding steel elements to wood beams to improve their load-bearing capacity. In the first case, the adhesives used may be relatively expensive and more difficult to apply, whereas in the second one, especially when steel elements are glued inside the glulam (GL) beams, it is better if the adhesives used are more accessible to apply and cheaper. As it seems rational to reinforce wood with high-modulus ties, research has been carried out to compare the connection quality of commercially available adhesives that can be used for this purpose. Moreover, thermosetting adhesives have been applied as an alternative and cheaper solution. Thermostat adhesives also have a high pH of the bond, which prevents the steel from rusting. The research shows that the load-bearing capacity of the bond depends on whether the bars are ribbed or sheet metal. Moreover, among thermosetting adhesives, the most favourable load-bearing values were obtained using a mixture of PF/pMDI (phenol formaldehyde resin/polymeric diphenylmethane diisocyanate) and powder from recycled tyres. The shear strength of these joints was 1.63 N/mm2 and 3.14 N/mm2 for flat specimens and specimens with ribbed bars, respectively.

Experimental investigations on the behaviour of structural-sized wood-CFRP composite beams in local fire

AbstractThe study involved combustion of 24 structural-sized beams under three-point bending subjected to substantial loading prior to ignition, reaching 90% of characteristic load-carrying capacity. A localised fire exposure zone was established proximal to the region experiencing the highest bending moment. The specimens were categorised into two groups: the first consisted of tituted by glued-laminated timber (B), and the second comprised wood-CFRP (carbon fibre reinforced polymer) composite (BW). Initial measurements encompassed pre-ignition static deflection and load. Subsequently, the specimens underwent controlled combustion, during which parameters including burning duration and deflection up to failure, were documented. Following cooling with sand, two cross-sectional slices were extracted from each fractured beam, enabling to find vector-based contours of the remaining cross-section. The charring rate and the approximate heat flux density for each test were determined, enabling a direct comparison of the results. A statistically significant number of specimens was examined, facilitating a comparative analysis between reinforced and unreinforced beams concerning failure time and form. Incorporating CFRP tapes among wooden constituents was found to increase the fire resistance of the structure, however, the thickness of the wooden material enveloping the CFRP composite emerges as a pivotal determinant. This issue needs thorough testing under standard fire in the future. Nevertheless, the fact is that adding CFRP tapes engenders a distinct form of beam collapse, transitioning from instantaneous cracking in B-beams to ductile failure in BW-beams.

Enhancement of mechanical characteristics and novel damage assessment for timber post and beam structures with K-braces

Glued-laminated Timber Post and Beam Structural System (GTPBSS) gains widely application in timber engineering because of direct force transmission and simple construction. The present work investigates the influence of introducing K-bracing on the lateral performance of the GTPBSS. To this end, four full-scale GTPBSS specimens with and without braces under horizontal loading conditions were carried out. The obtained test results highlight that the GTPBSS without braces exhibited large deformation. The failure modes predominantly centered on the occurrence of wood cracking at both the column-base joint and beam-column joint. In contrast, the GTPBSS specimens equipped with K-bracing elements exhibited failure modes marked by the instability of the brace components. The inclusion of brace system within the GTPBSS structures yielded positive results, effectively reducing lateral deformations while concurrently augmenting both the elastic stiffness and the later maximum load-carrying capacity. However, it is essential to exercise caution with regard to potential out-of-plane instability. A dual-parameter damage assessment model was developed to evaluate structural damage, incorporating factors related to energy dissipation and deformation. The evaluation results derived from this model were consistent with the test results, affirming the rationality and validity of the proposed approach. This model is expected to provide a scientific foundation for formulating strategies for repair and maintenance.

Analysis of the Bending Behaviour of T-Shaped Glulam Beam

Glulam, a sustainable manufactured wood product, is gaining prominence for its numerous advantages. The current study employed an analytical approach using a finite element model developed in ANSYS Workbench 2023 R2 to investigate the flexural properties of glued-laminated timber beams compared to solid T beams. This research focused on assessing the impact of different lamina thicknesses on glulam beams using Larix wood. Glulam beams were categorized into three groups based on lamina thickness: 30 mm, 15 mm, and 10 mm. Additionally, solid T beams were modelled for comparison. Both solid and laminated wood from Larix species were evaluated using ANSYS 23.2. Glued-laminated timber is produced by adhering to graded-sawn timber pieces to fabricate a robust engineered material. This study assesses the flexural properties of T-shaped glued-laminated timber beams and their comparison with solid T-beams.

Bending and compressive properties of glued-laminated timber composed of Japanese white birch wood using casein adhesive

ABSTRACT Size-reduced model glued-laminated timber (GLT) (1/8 cross-sectional size, six layers, 11 by 18 by 430 mm) was manufactured using birch (Betula platyphylla) wood and a casein adhesive to evaluate the possibility of producing the structural GLT without petrochemical-based adhesives in Mongolia. The same-sized solid lumber and GLT using aqueous vinyl polymer solution-isocyanate adhesives (API) that can be used for structural GLT production in Japan was prepared to evaluate the mechanical performance of GLT using casein adhesive. The effects of lamination configuration and patterns on the mechanical properties (dynamic Young's modulus, modulus of elasticity [MOE], modulus of rupture [MOR], bending work [energy until broken, W], and compressive strength [CS]) were also evaluated using mixed-effect model. Almost no significant differences in the bending and compressive properties were found between GLT using casein and API adhesives, suggesting that, in dry conditions, the bonding performance of casein adhesives closely matches that of API. Modeling results showed that lamina configuration influenced the W and CS even in the Young’s modulus was almost the same, suggesting that the basic wood properties, such as load and deflection characteristics, are important to enhance the mechanical properties of birch GLT with casein adhesive by laminae configurations.

Mechanical characterization of glued laminated timber (glulam) beams produced with rubberwood and green polyurethane adhesive

Increasingly, efforts have been made to replace adhesives that contain formaldehyde in their formulation with others free of this substance in the production of engineered wood. It is known that the release of formaldehyde can cause serious problems to human health, potentially leading to death. As a result, the use of formaldehyde-free adhesives has gained prominence in industries. Furthermore, a major challenge in the use of wood products refers to their durability, which can be reduced by the attack of xylophagous agents. The use of preservative solutions is an alternative that mitigates this problem and guarantees greater durability to the material. Therefore, the objective of this work was to evaluate the mechanical properties of glulam beams produced with rubberwood treated with preservatives chromated copper borate (CCB) and pyrethroid using polyurethane as adhesive, a type of free-formaldehyde adhesive. The glulam beams were produced with 3 lamellas measuring 60 × 20 × 1200 mm, differentiated by the type of adhesive (polyurethane and resorcinol-formaldehyde), and by the presence or absence of preservative treatment. Specimens were obtained from the beams for characterization regarding resistance to normal compression, structural compression, and compression parallel to the fibers in dry and wet conditions. Among the properties evaluated, it was found that preservative treatments did not affect the compressive strength parallel to the fibers in beams produced with polyurethane, with values ​​of 33.77 and 31.61 MPa for those without treatment and treated with CCB, respectively, not showing significant differences. These results show the potential for using polyurethane as an adhesive in glulam beams.

Evaluation and prediction of bending properties of glulam beams made from young plantation-grown Eucalyptus nitens

ABSTRACT Interest in making glulam from plantation-grown Eucalyptus nitens has increased, but current structural timber standards were not designed for species grown in plantations. Additionally, the applicability of classical composite beam theory remains uncertain due to the unique features of this species. This study was designed to assess the hypothesis that the bending performance of glulam made from young plantation-grown E. nitens is reliable and predictable. We tested the hypothesis through experimental procedures and theoretical and statistical analyses. First, we assessed the bending performance of 20 glulam beams, which were manufactured in five configurations. Second, we compared our experimental results with predictive values to evaluate the accuracy of methods in current standards. Third, in our pursuit of improved predictive tools, we developed theoretical and parametric models using mechanical properties of the board elements. Our improved models showed a decreased deviation in both stiffness and strength values. A Monte Carlo simulation was used to determine the distribution for both stiffness and strength. The results validated that this product can be allocated a GL grade using current standards and the bending performance is predictable. The study enhances confidence in incorporating E. nitens into glulam products and offers valuable data for future specification modifications.

Cyclic Behavior of Bolted Glued-Laminated Timber Brace Connections with Slotted-In Steel Plates

Cyclic Behavior of Bolted Glued-Laminated Timber Brace Connections with Slotted-In Steel Plates