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A feasibility study of glulam was carried out in French Guiana using local wood species. The aim was to determine gluing parameters affording satisfactory behaviour to manufactured glulam in a tropical climate. Three abundant wood species, with special properties, were selected for the study and resorcinol–phenol–formaldehyde resin was used for bon...
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... Glued-laminated Timber Post and Beam Structures (GTPBS), renowned for their renewable, lightweight, high-strength, and ecofriendly attributes, have found widespread use in timber buildings, primarily owing to their outstanding seismic performance [1,2]. However, under the influence of a severe earthquake, GTPBS are bound to sustain damage to some extent. ...
... Therefore, the non-linear model elaborated in this paper can be an alternative and effective tool that engineers and designers can use properly to assess the stability of slender glulam subjected to risk of flexuraltorsional buckling failure. As there is no standard on the use of hardwood glulam for structural purposes, 47 the model developed in this work could be considered as a significant step forward in the development of high performance engineered tropical wood products such as glulam. ...
The main objective of this manuscript is to model the flexural-torsional buckling of slender tropical glulam beams using the finite element method. The non-linear approach to quantify both the buckling strength and the lateral geometrical
features of wooden beams is proposed. A very rigorous methodology is used which is based on the kinematic Vlasov’s theory to determine the displacement field of the beam section by considering an updated Lagrangian description. For the finite element discretization, the Author develop a single wood element characterized by 14 degrees of freedom, i.e. seven degrees for each nodal point, and derive non-linear stiffness matrices by using the virtual works principle. The model is implemented in MatLab and the numerical results are compared with results based on the classical linear stability
theory of slender wood beams. The selected case-studies are a cantilever beam and a beam on two supports.
... For that reason, hardwood bonding is no trivial task. Hardwood often shows different behavior when glued [3][4][5] because of its different structure, wood chemistry [6], and extractive content [7] compared to softwood. Hardwood also has a higher susceptibility to swelling and shrinkage (especially beech wood) [1],and a strength parameters. ...
... In addition to verifying these assumptions, the aim of this paper is to verify whether the gluing of beech and hybrid elements using PUR adhesive is suitable since the researchers used different adhesives in most of the above-described studies (e.g., [2,3,13,22,23,32]). In study [7], PUR adhesive was used for gluing hardwood glulam members that were thermally loaded and that then underwent bending tests. ...
The aim of this work was to verify the behavior of hybrid hardwood glue-laminated beams and the possibility of replacing Norway spruce (Picea abies) construction elements, especially in roof and ceiling structures. The samples were six lamellae homogeneous beech (Fagus sylvatica) beams and six-lamellae hybrid beech-poplar (Fagus sylvatica–Poplar spp.) beams; each beam had a cross-section of 60 × 120 mm and was glued with polyurethane adhesive. The samples were loaded using destructive four-point bending tests according to EN 408; the obtained bending strength and modulus of elasticity were statistically evaluated and compared to each other in both types of samples. The results showed that the examined properties of the hybrid beams (with a 16% weight reduction) are comparable to the properties of homogeneous beech glue-laminated beams. Based on the obtained data, the timber elements that are currently used can be successfully replaced by hardwood glue-laminated elements. Based on their higher load-bearing capacity, the cross-section depth can be reduced compared to a larger cross-section depth in spruce beams; this means that hardwood could be suitable in building renovations.
... In glulam, the defects in the sawn timber are cut out, and lamellas with a thickness of ≤50 mm are bonded together [2]. Glulam beams can be made from coniferous woods (Douglas fir, larch, Norway spruce, hemlock, Southern pine, etc.), broadleaved woods (azobé, beech, doussie, keruing, padouk, red maple, resak, etc.), as well as densified low-density woods (batai, poplar, etc.) [2][3][4][5], preferentially using thermosetting glues such as polyurethane (PUR), resorcinol-formaldehyde (RF), phenol-resorcinol-formaldehyde (PRF), melamine-formaldehyde (MF) or urea-melamineformaldehyde (UMF). In Europe, the Norway spruce is the most common wood species used for glulam [2,5,6]. ...
Glued laminated (glulam) beams are used in the roofs, ceilings and walls of buildings as well as in bridges and towers. At present, with the limitation of tree harvesting, the production of glulam beams from recycled wood sources is implemented with the proviso that their mechanical properties and resistance to pests, fire and weathering will not be aggravated. This work deals with the primary effect of aging Norway spruce wood (Picea abies Karst. L.) lamellas on the moduli of rupture (MOR) and elasticity (MOE) in bending of three-layer glulam beams composed of sound and aged lamellas and polyurethane (PUR) glue. Three methods of lamella aging were used: (A) natural, lasting 60 years in the form of roof trusses with a greater or lesser degree of bio-attack by woodworm (Anobium punctatum De Geer); (B) artificial, caused by increased temperatures from 160 to 220 °C for 4 h; (C) artificial, caused by 2% water solutions of inorganic preservatives, namely, CuSO4 x 5H2O, ZnCl2, H3BO3 or (NH4)2SO4, for 28 days. The lowest MOR values were determined for glulam beams in which all three lamellas or two surface lamellas had a greater degree of bio-attack (60.5 MPa, a decrease of 25.9%) or were exposed to primary aging at 220 °C (62.6 MPa, a decrease of 23.3%). On the contrary, the exposure of lamellas to 160 or 180 °C did not significantly influence the MOR of beams (76.0–82.7 MPa, an average decrease of 1.6%). The MOE of glulam beams ranged from 7540 to 10,432 MPa without an obvious influence of the method of lamella aging or their location in the beams. Linear correlations between the MOR or MOE of glulam beams and the shear strength (σ) of glued joints, if both composite types consisted of similarly aged lamellas, were only slightly significant or insignificant.
... The study confirmed that the use of pressed timber layers as a reinforcing material is economically and environmentally effective. Another study [21] presented an investigation of the feasibility of glulam beams, the purpose of which was to determine the effective gluing factor, stating in its conclusions that the gluing parameters must be adjusted depending on the timber species. Another study [22] presented an investigation of the mechanical properties of the glue in a rod embedded in a glulam beam, where the results of an experimental pull-out test of this rod showed that failure occurred as a result of the rod slipping into the glulam beam and the delamination of the shear bond. ...
Changes in the condition of existing timber structures can be caused by fatigue or biological attack, among other things. Replacing damaged timber is still very expensive, so it seems more advisable to repair or reinforce damaged elements. Therefore, in order to improve the static performance analysis of timber structures, reinforcement applications in timber elements are necessary. In this experimental study, technical-scale glulam beams measuring 82 × 162 × 3650 mm, which were reinforced with carbon strands and carbon laminates, were tested in flexure. A four-point bending test was used to determine the effectiveness of the reinforcement used in the timber beams. Internal strengthening (namely, glued carbon cords placed into cut grooves in the last and penultimate lamella) and an external surface of near-surface mounted (NSM) carbon laminates glued to the bottom surface of the beam were used to reinforce the laminated ashlar beams. As a result of this study, it was found that the bending-based mechanical properties of ash wood beams reinforced with carbon fibre-reinforced polymer composites were better than those of the reference beams. In this work, the beams were analysed in terms of the reinforcement variables used and the results were compared with those for the beams tested without reinforcement. This work proves the good behaviour of carbon fibre reinforced plastic (CFRP—Carbon fibre reinforced polymer) cords when applied to timber beams and carbon laminates. This study illustrated the different reinforcement mechanisms and showed their structural properties. Compared to the reference samples, it was found that reinforcement with carbon strings or carbon laminates increased the load-bearing capacity, flexural strength and modulus of elasticity, and reduced the amount of displacement of the timber materials, which is an excellent alternative to the use of ashlar and, above all, inferior grade materials due to the current shortage of choice grade. Experimental results showed that, with the use of carbon fibre (carbon cords SikaWrap® FX-50 C—Sika Poland Sp. z o.o., Warsaw), the load bearing capacity increased by 35.58%, or with carbon cords SikaWrap® FX-50 C and carbon laminates S&P C-Laminate type HM 50/1.4 - S&P Poland Sp. z o.o., Malbork, by 45.42%, compared to the unreinforced beams.
... However, this does not mean an end to research into this material. This research is generally concerned with several aspects, i.e., assessing the quality of beams made of hardwood species [3][4][5][6][7][8][9], the introduction of new species from the tropics [10][11][12][13][14][15], FEM numerical modelling [16][17][18][19][20], and load-carrying capacity improvement, most often by strengthening the beam in the tension zone [21][22][23][24][25]. Continental pine wood, in general, is troublesome for the production of structural components because it has numerous knots, occupying up to 50-70% of the surface area of a given piece of lumber. ...
This study aimed to evaluate the mechanical properties determined in a 4-point bending test of beams made of lumber from which knots had been locally removed and the resulting loss replaced with sound wood. Three sets of beams were prepared, which differed in the number of layers/lamellas and the position of the lamellas from which edge knots were removed. All the lamellas used in the tests were subjected to a modulus of elasticity assessment. In addition to the distribution of defects, it determined the position of a given piece in the beam structure. The tests showed that high mechanical properties could characterise the beams produced in this way, i.e., a modulus of elasticity close to 12 kN/mm2 and a strength above 40 N/mm2, if the lamellas without knots were located below the outer tension lamella. Significantly better results were obtained when PUR glue was used in the inserts rather than MUF. In this case, beams with an improved outer lamella in the tension zone using semi-circular inserts glued with PUR glue had an average strength of 34.6 N/mm2.
... Despite the potentials described previously, glulam assembling from tropical hardwoods, especially those from the Congo Basin, generally suffers from a lack of understanding at that international level (Teles et al. 2013). As there is no standard on the use of hardwood glulam for structural purposes (Bourreau et al. 2013), one solution consists of mastering the design of the bondlines. ...
... This requires preliminary seasoning of the wood moisture content below the fibre saturation point (FSP), from 9% to 14% (Lipke 2005). Since several species are characterised by properties such as a high volumetric weight, high shrinkage coefficients and the presence of resins, they are prone to severe deformations or cracks that may occur during the drying process (FCBA 2008;Bourreau et al. 2013). Some defects are visible (superficial cracks and severe deformations like twists, cups and bows), while others may not be readily apparent (internal cracks). ...
... The durability of green GLT manufactured by using heavier timber species like bilinga, tali and azobe could be ensured by optimising the whole set of gluing parameters. That approach was analysed in the literature by Bourreau et al. (2013) who investigated the feasibility of glulam by using some French Guiana tropical timber species and a PRF resin. ...
The development of glulam may give complementary, added-value to an important part of the timber production
in the Congo Basin. Nevertheless, the high humidity in which these timbers operate may cause problems such as
cracks and severe deformations if they are not suitably bonded. Moreover, there is a lack of knowledge concerning
the refined design of the bondlines of glulam assembling from the Congo Basin hardwoods. We investigated the
durability, mechanical strength, and variability features of the bondlines, manufactured under higher moisture
conditions. Eight hardwood species with very different properties were selected. A one-component polyurethane
adhesive was used. Industrial gluing parameters were kept constant. Delamination, shear tests and analysis of
bondlines thickness were carried out. Multivariate analysis and a goodness-of-fit test of the strength variability
of the bondlines were performed. Optimum bondlines thicknesses were obtained. Their durability exhibited
satisfactory trends up to a density of 750 kg/m3. The behaviour of the bondlines can operate in three homogeneous
groups. In each of them, the variability of the shear strength can be properly modelled using a 3-parameter Weibull
probability. Wood failure trends were in accordance with several international requirements. The density value of
750 kg/m3 appeared as critical for the compatibility between the shear strength, the durability and the bondlines
thickness. The overall results showed the ability of several tropical timber species to be valorised in green-glulam
applications. Moreover, the findings unlock new trends concerning a reliable and safe design of tropical glulam as a
structural wood-based product.
... However, the problem encountered concerns the bonding pressure, the dimensions of the adhesive joint (bonding surface), and also the fit between the adhesive and the substrate. [6] investigates the finger joints of different types of hardwoods. He states that bonding-related factors such as adhesive application, pressing time, and applied pressure depend on joint strength. ...
The design of structural elements, the design of connections and supports, and damage have a significant influence on the technical characteristics of wood construction projects. An innovative experimental study was carried on locally obtained glulam beams. This study aimed to evaluate the load-bearing capacity of a finger-jointed Terminalia Superba (fraké) lamellae during routine use of an adhesive in the local area and to improve the connections in glulam structures. The achievement of this objective will allow to determine the influence of the technical characteristics of finger-jointing on the mechanical resistance, to maximize the mechanical resistance of the reconstituted beams, and eventually to minimize the losses due to sawing. All this will have a considerable impact on the technical and economic aspects of a wood construction project. The physical aspect of the species was studied and properties found. The influence of variation in density, the bonding surface, and joint efficiency on the bending strength (MOR) of Terminalia Superba (fraké) was studied. Mechanical properties were found and related to the optimum joint angle α, and the breaking point reads 0.20 mm. For the angular range of [0°–30°], adhesive failures are witnessed, and beyond this range, the failures are mixed. The 45° finger-jointing angle appeared to be better in the axial traction mode of rupture.
... In the study of Anshari et al. 10 , compressed wood (CW) blocks were used to strengthen the glulam beams and the specimens were tested later, the study proved that using CW as a reinforcement material is economically and environmentally effective. The feasibility of glued laminated timber beams was studied by Bourreau et al. 11 , the aim was to find the gluing factors which offer satisfaction behavior of glulam was done, where the results of delamination tests showed that the gluing parameters need to be adjusted depending on the wood species. Navaratnam et al. 12 presented an experimental study for investigating the mechanical performance of glued-in-rod (GIR) embedded in glued-laminated timber (GLT) beam where the results of the pull-out test revealed that the failure occurred by the interface GIR to GLT slippage and shear bond delamination. ...
Most existed researches consider deterministic numerical analysis when dealing with structural models. However, the test results reveal that uncertainties are existing in most cases regarding some considerations such as material randomness and the lack of experience. Therefore, proposing a probabilistic design models have got attention of researchers according to its important role in predicting accurate performance of the structures. The aim of the proposed work is to consider reliability-based analysis in numerical modelling of glulam beams reinforced with CFRP plates as well as unreinforced glulam beams by considering the properties of used timber material as random variables having mean value and standard deviation taking into consideration that the findings of this study have shown that the reliability index is worked efficiently as a limit which controls the process. Hill yield criterion model is adopted with respect to the data which is obtained from the experimental tests in order to validate the models. Furthermore, a detailed comparison between the reinforced and unreinforced glulam beams are proposed to see the effect of introducing the CFRP plates as a reinforcement material. The results of this study have successfully given a deep understanding of how the uncertainties plays a crucial role on the resulted deformations and stresses in which it was founded by making a comparison between deterministic and probabilistic numerical analysis.
... In the case of structural timber, finger joints are common. Many studies have tested and investigated these joints as applicable for bonding structural timber and in the furniture industry [14][15][16][17][18]. Various authors indicate different ranges of joint length from 6 mm to 25 mm, which may be used in structural timber [19][20][21]. ...
Numerous studies have shown that the geometry of micro-joints significantly affects the strength of the so joined timber element. The bending strength increases by creating a larger bonding area by increasing the length of the wedge joint. Although this type of joint has been successfully used for many years, it can still be troublesome to make. For these reasons, the present study investigated an easy-to-fabricate wedge joint, which we folded during the beams’ formation and glued with the same adhesive as the individual lamellas. Although the research has not fully answered all the questions relevant to both scientific and technological curiosity, it indicates the great potential of this solution. Following the principle adopted in the ongoing wood optimisation work, we concluded that the beams of the target cross-section should be produced, and it should only be possible to cut them to a certain length. In this approach, we only removed defects at critical points for the beam structure and, in this way, up to 30% of the timber processed could be saved or better utilised.
