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Timber structures and buildings made from sustainable forestry might be the solution for today's ecological challenges when their renewable materials are locally processed with low energy consumption in production. The current market shows a dominance of rectangular cross-sections in engineered timber solutions. Roundwood – a traditional material in the past – is no longer common due to a lack of applications in modern structures, lost knowledge in handcraft skills and the high costs of computerised numerical control-based manufacturing. However, solid timber with a round cross-section outperforms other engineered wood products, such as glued laminated products, in terms of energy consumption and environmental aspects. To overcome restrictions in joint technologies and to increase the usability of roundwood, especially in truss structures, a new type of connector was developed. The investigation was split into two research topics: the connection design in roundwood with modified bonded-in rods and the design of wood-fibre composite moulded connectors, which is described in this paper. [ABSTRACT FROM AUTHOR]

Bamboo is a fast-growing biobased building material with a high strength-to-weight ratio, and the combination of bamboo and wood provides an environmentally friendly alternative for building construction. A new type of laminated bamboo–timber composite column was proposed to improve the compressive performance of timber columns, which was expected to obtain better mechanical performance. Bamboo scrimber and Douglas fir were combined to form laminated bamboo–timber composite columns for the experimental study. Axial compression tests were carried out on 5 groups of 15 composite columns. The failure modes of the composite columns were assessed. The laws of axial displacement, lateral displacement, axial strain, ultimate bearing capacity and stiffness were analyzed. Finally, the bearing capacity of the composite columns was calculated by referring to the design specification for timber structures. The results indicated that the composite columns exhibited three failure characteristics. The ultimate bearing capacity and stiffness of the bamboo–timber composite columns increased with increasing amount of bamboo scrimber. The ultimate load of the bamboo–timber composite columns was increased by 23.0–94.6%, while the stiffness was increased by 9.1–38.4%. In addition, the bearing capacity of composite columns was calculated according to two standards. The experimental values of the bamboo–timber composite columns are in good agreement with the theoretical values, and the errors are within 8%. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Shear connectors ensure effective interaction between wood beams and concrete slabs of composite beams, and their properties noticeably affect the fire resistance of timber-concrete composite beams. To investigate the shear stiffness of notched connectors in glued laminated timber (GLT)- concrete composite beams under fire conditions, 16 shear tests were conducted. The effects of fire duration and notch length on shear properties of the connectors for a given spacing were studied. The fire tests indicated that the reduction of the notch length from 200 mm to 150 mm remarkably affected the failure mode of the shear specimens, changing from compression failure of notched wood to shear failure of notched concrete. The increase in fire duration reduced effective width of the notched wood, negatively affected the shear stiffness and shear capacity of the connectors, and the shear stiffness decreased more rapidly. The notch length did not have a substantial effect on the shear stiffness of connectors. Based on the experimental results, an analytical model to estimate the shear stiffness of notched connectors in GLT-concrete beam under fire conditions was established. [ABSTRACT FROM AUTHOR]

Experimental tests of Cross Laminated Timber (CLT) under in-plane beam loading conditions are presented. The influence of the element layup, the individual lamination width, and the beam overhang at the supports on the shear force capacity was investigated. All the CLT beams had the same gross cross section, and a 4-point-bending test setup was used. The experimentally determined load-bearing capacities are compared with the load-bearing capacities resulting from analytical methods proposed for structural design, focusing on shear failure in the crossing areas of flatwise bonded laminations (shear failure mode III). The test results indicate no or very small influence of the element layup and the lamination width on the shear force capacity. These results partly contradict the predictions of the proposed design methods. Of the three studied beam geometry parameters, the beam overhang at the support had the greatest influence on the load-bearing capacity. • Lamination width was found to have small influence on load-bearing capacity. • Element layup was found to have small influence on load-bearing capacity. • Beam overhang length was found to influence the load-bearing capacity. • Test results are partly in disagreement with available design proposals. [ABSTRACT FROM AUTHOR]

Glue-line tests provide the shear resistance and failure mode of samples extracted from laminated timber products. Several papers questioned the practical use of such tests affirming the lack of correlation between the capacity of the beam and the outcomes of glue-line tests. However, no studies provide a probabilistic framework for interpreting glue-line tests. This paper presents and discusses the largest database of glue-line tests ever published, consisting of approximately 17000 tests on glued laminated timber (GLT) beams, carried out at the Treteknisk, the Norwegian Institute of Wood Technology (Norway). This database has been used to develop in Abaqus a stochastic FE model to predict the shear capacity of glued laminated timber beams (GLT) using advanced modelling concepts, including discrete cracking and plasticity. The authors examine the dependence of the shear capacity on the beam size to assess the shear size effect in GLT components. The methodology is based on Montecarlo simulations. The mechanical properties of the elementary volumes composing the beam are assigned using a random field model calibrated on the glue-line tests. • Screw reinforcement for timber specimens under compression perpendicular to grain. • Experimental tests on 54 specimens with different geometry and load conditions. • Validation of the capacity model according to the Eurocode 5 proposal. • The model does not seize the failure mechanism by the screw tips. • The model is slightly conservative for the failure by the load steel plate. [ABSTRACT FROM AUTHOR]

The present paper focuses on the analysis of tensile stresses perpendicular to the grain in both standard and non-standard simply supported beams made of glued laminated timber. The beams are analysed using two methodology approaches: a code design verification method and a finite element method (FEM) in terms of the linear theory of elasticity with plane stress assumption. The analysis is performed for various material parameters both isotropic and orthotropic, proving that both methodologies lead to consistent results in the case of standard glulam beams and therefore the FEM can be used in the case of non-standard structures, which are not included in Eurocode 5. [ABSTRACT FROM AUTHOR]

An experimental program has been conducted to address the impact of relaxing the laminae modulus of elasticity (MOE) requirements on the strength properties of Canadian glulam columns. The database established column capacity versus length information. Furthermore, the test data shows that the MOE of the glulam specimens was slightly higher than the code specified value even though the tested glulam was manufactured with laminate having lower MOE than the code requirements. A framework for reliability analysis of Canadian glulam columns has been formulated. The procedures take into consideration the randomness of the effects of applied loads and the column resistance. Two approaches have been used to model the randomness of the column capacity: (1) calibrated Cubic Rankine Gordon curve (CRG) approach with random representation of σ c and E ∗ and (2) column capacity distribution fitting. Results show the performance of glulam made with new laminae grading rules exceeds the target reliability for structural wood products in Canada. [ABSTRACT FROM AUTHOR]

Within the last 20 years, cross laminated timber (CLT) has become one of the most important building products in contemporary timber engineering. By the end of this decade, its annual worldwide production volume is expected to exceed 1,000,000 m 3 . The industry, engineers, architects and constructors have a strong interest in implementing CLT in European product, design and execution standards. The design of CLT is part of the currently ongoing revision of Eurocode 5. In this context and in addition to the verification of CLT panels in respect of ultimate and serviceability limit states, guidelines on the design of connections in CLT with dowel-type fasteners are of the utmost importance. In this article, we review approaches for calculating characteristic values as provided in literature for single dowel-type fasteners and connections in CLT. We also compare these approaches, with focus on withdrawal and embedment strength of dowels, nails and self-tapping screws, with the current regulations on dowel-type fasteners for solid timber and glulam as formulated in Eurocode 5. These comparisons are made in order to identify the need and potential for revision of current EC 5 equations and state-of-the-art regulations. We summarise regulations on connection design, i.e. minimum spacing, edge and end distances, other additional geometrical conditions, regulations on the effective number of fasteners in a group and minimum penetration depths. Finally, we draw conclusions in respect of the single fastener properties withdrawal and embedment strength and suggest some execution guidelines, which ensure the integrity of CLT structures. Overall, we aim to present a compilation of the current state-of-the-art knowledge on dowel-type fasteners in CLT as a basis for implementing design guidelines for CLT in the new connection chapter of Eurocode 5. [ABSTRACT FROM AUTHOR]

In glued-laminated timber (glulam), fracture may occur at the interface of two adjacent laminae that mostly have different growth ring orientations. The double cantilever beam (DCB) tests for Mode I fractures and three-point bending end-notched flexure (3ENF) tests for Mode II fractures were performed to obtain the interlaminar fracture toughness of glulam with focus on the influence of growth ring orientations. Experimental and numerical results show that the effect of growth ring orientations of two adjacent laminae on Mode I and Mode II interlaminar fracture toughness is slight. [ABSTRACT FROM AUTHOR]

This paper describes an experimental test program and theoretical analysis which examines the reinforcing in flexure of glued laminated timber (glulam) beams using fiber reinforced polymer (FRP) and steel materials. A series of four-point bending tests were conducted till failure on both unreinforced and reinforced Douglas fir glulam beams in a simply-supported scheme. The focus of this research was to evaluate the effects of reinforcing materials, reinforcement ratio and arrangement on the flexural behavior. Test results showed that the flexural capacity, flexural global stiffness and timber tensile strain at failure were all improved considerably for reinforced timber beams when compared to the unreinforced control beams, in which the average improvement reached 56.3%, 27.5% and 49.4%, respectively. On the bases of the experimental results, a theoretical model was proposed to predict the flexural capacity and flexural stiffness of the reinforced timber beams. Most of the differences between theoretical and experimental results for both flexural capacity and flexural stiffness were within 10.0%, which showed a high accuracy of the proposed model. Subsequently a parametric analysis, which includes the axial stiffness ratio of reinforcement to timber, the relative location of tensile reinforcement, and the strength ratio of reinforced timber between flexural tension and compression, was undertaken to investigate the effects of the influential factors for both flexural capacity and flexural stiffness. [ABSTRACT FROM AUTHOR]

The bamboo industry plays a significant strategic role in the world's economy. Laminated bamboo, with increasing yearly yields, is the intermediate material for bamboo products such as furniture, floor board, and container floor. The trilaminar straight joint glued-laminated bamboo production line is the leading enterprise in Fujian Province, and it was used to conduct a load analysis of the data collected from a year's production, based on the life cycle assessment system. The results show that the processing of glued-laminated bamboo contributes notably to the acidification potential, eutrophication potential, global warming potential, and photochemical ozone creation potential, whereas resource depletion and ozone depletion are affected by the urea-formaldehyde resin adhesive, among which the urea contributes the most. As for processing, carbonization, desiccation, and thermo-compression, these have the greatest impacts on the environmental load, with a total contribution rate of greater than 67%, as the main source for the power depletion is from the processing of fossil fuel. In addition, the oxynitride, phosphide, sulfide, aromatic hydrocarbon, etc., that are discharged from the reaction intensify the eutrophication potential, the photochemical ozone creation potential, and the acidification potential. [ABSTRACT FROM AUTHOR]

• The use of stiff shear-key connectors in multi-panel CLT shear-walls is investigated. • An experimental campaign at joint and wall level on shear-key connectors is conducted. • The behaviour of shear-key connectors is compared to that of screwed connections. Multi-panel Cross Laminated Timber shear-walls with stiff vertical joints may represent a valuable structural solution for multi-storey timber buildings in low seismic prone areas. In this study, the opportunity of using shear-key connectors in the assemblage of stiff vertical joints as an alternative to short-spacing traditional dowel-type mechanical fasteners is evaluated. The mechanical behaviour of two types of stiff shear-key connectors is investigated through an experimental campaign conducted at joint and wall level. Shear tests were firstly carried out to determine the mechanical properties of panel-to-panel joints assembled with the shear-key connectors. The results are compared with those obtained from shear tests on joints with screwed connections (half-lap and spline joints). Full-scale shear-wall tests were then performed to determine the mechanical performances of the connectors at wall level. Joints with a single shear-key connector showed values of stiffness and strength comparable to those that would be obtained for vertical spline joints with approximately thirteen couples of 6 mm screws. The failure modes on the joints with shear-key connector were characterized by either a localized crushing in the wood or the shear failure in outer lamination of the CLT panels with no plastic deformation of the connectors. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of subfreezing temperatures and moisture content on the shear behavior of glulam beams. Full-scale glulam beams (79 mm by 229 mm deep) at two moisture contents (12 and 28%) and three temperatures (20 °C, 0 °C, and − 40 °C) were tested in four-point bending until failure. Temperature was observed to affect the failure mechanism of the beams, with the beams tested at 0 °C and 20 °C failing in shear and the beams tested at − 40 °C failing in tension. Further, the strengths of the beams and their stiffnesses were observed to increase with decreasing temperature, with these effects being more pronounced in the higher moisture content beams. Over the temperature range of 20 °C to − 40 °C, the 12 percent moisture content beams observed strength and stiffness gains of 17 and 22%, while the 28 percent moisture content beams observed respective gains of 37% and 66%. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the results of a comprehensive experimental study of joints made with threaded steel bars glued with epoxy in both parallel and perpendicular directions to the timber fibres. Two types of wooden products, namely, glulam and laminated veneer lumber (LVL), were used due to their widespread use in notable timber engineering designs. Experimental results showed that the behaviour of glued joints with bars parallel and perpendicular to the timber fibres differed, depending on the slenderness of the joint. It was also observed that specimens made with LVL had lower strength than those made with glulam, regardless of whether the anchors were parallel or perpendicular to the fibres. [Copyright &y& Elsevier]

Abstract: Treatment options for outdoor above-ground (H3) glulam of Pinus radiata and P. elliottii were examined. Beams were treated with azole LOSP to retentions of ∼40 L/m3 or ∼70 L/m3 either before or after gluing. TBTN-LOSP and CCA were included for comparison. Test specimens were exposed for four years outdoors in the wet tropics at Innisfail or in an accelerated field simulator (AFS) in horizontal or vertical orientation. Decay was 2.5 times faster at Innisfail than in the AFS. Glulam treated before gluing generally performed better than glulam treated after gluing, whether vertically or horizontally exposed. One exception was horizontally exposed specimens in the AFS, perhaps as treated wood is not lost upon dressing when treated in final form. Nevertheless, as glulam failure mostly occurs at ends, treatment before gluing provides better protection of individual laminates, especially important when beams are docked to size. End grain protection can be improved by resealing, and copper naphthenate was more effective than zinc naphthenate. [Copyright &y& Elsevier]

Abstract: With the aim of evaluating the bond behaviour between glulam and carbon fibre reinforced polymer laminates strips, an experimental program using pull-out tests was carried, when the near-surface strengthening technique is applied. Two main variables were studied: the bond length and the type of pull-out test configuration. The instrumentation included the loaded and free-end slips, as well as the pull-out force. Based on the obtained experimental results, and applying an analytical–numerical strategy, the local bond stress–slip relationship was determined. In this work the tests are described, the obtained results are presented and analysed, and the applicability of an inverse analysis to obtain the local bond law is demonstrated. [Copyright &y& Elsevier]

The article presents a study which examines how manufacturing defects in glued laminated wood beams may lead to further cracking effects of laminated component layers. The study demonstrates the dependence of a wooden laminated beam's yield mode along the extreme fixture line on the laminate thickness. Moreover, it illustrates how thinner laminates yield by shearing around the fixture area and thicker laminates from combined fractured ways.

• Effect of manufacturing pressure and fibre type on properties of FRP-timber (HFT) laminates was studied. • Increase in pressure was found to improve membrane elastic properties but reduced the flexural stiffness. • HFT made using Glass fibres was found to provide best membrane properties. • Both HFTs with natural fibres and HFT made using glass fibres found to have similar flexural properties. • Classical laminate theory was found to be inaccurate in deriving HFT laminate flexural properties. Hybrid fibre reinforced polymer (FRP)-timber (HFT) thin-walled structural members made out of thin-timber veneer and fibre reinforced polymer composite laminates are a sustainable alternative to light-weight steel and aluminium thin-walled structural members. Preliminary studies on HFT structures have demonstrated the potential of HFT thin-walled structures to be used as high performing structural members. This study is aimed at investigating the effect of manufacturing pressure and the fibre type on the mechanical properties of the HFT laminates. Two different manufacturing pressures and three types of FRPs were used in the investigation. Series of experiments were carried out to determine the tensile, compressive, shear, and flexural properties of the laminates. Best manufacturing pressure as well as the fibre type to use were found to be dependent on the type of loads (membrane and/or flexural) applied on the HFT laminate. Classical laminate theory was found to be accurate in calculating membrane properties of the HFT laminate, but was found to result in significant inaccuracies when calculating the flexural properties. [ABSTRACT FROM AUTHOR]

Current advances in timber engineering with the use of timber at longer spans necessitate the use of high performance joints. Glued-in rods exhibit high axial load capacity and stiffness and are suitable for such applications. FRP rods can increase their durability and fire performance but ways to produce progressive failure mechanisms are necessary to enhance their resilience. In this study CFRP and GFRP rods glued in block laminated timber with epoxy are investigated under both monotonic and cyclic loading. Joints with constant glue-line thickness and variable bond-line geometry are studied to induce progressive resin failure mechanisms. A stepped wedge shaped geometry with varying glue-line thickness and a mirrored version were investigated. The effect of elastic modulus (CFRP vs GFRP) and glue-line thickness on the bond strength, stiffness and material viscous damping are explored. CFRP rods exhibit 11% higher axial load capacity under monotonic loading but GFRP rods exhibit higher bond stiffness at the serviceability stage. The cyclic loading does not discount the bond performance and results in higher stiffness due to viscoelastic creep deformation. An increase in glue-line thickness results in higher axial withdrawal capacity and viscous material damping. Specimens with a wedge shaped bond-line exhibit superior mechanical performance. An FEA model is presented for a variable bond-line geometry and the numerical results agree well with the experimental findings. [ABSTRACT FROM AUTHOR]

This paper summarizes the results of an experimental study on the rotational behavior of bolted beam-to-column glulam connections reinforced using locally cross-laminated glulam members. Twenty-two full-scale connection specimens were tested through monotonic and reversed cyclic loading, from which the moment / rotational angle relationships were established. The results indicated that the cross-laminated technique leads to a more ductile failure mode with cross-aligned inner layers of laminas fractured, in contrast to the perpendicular-to-wood-grain tensile failure of unreinforced connections. The connection maximum moment was found to increase by 52% and 46% under monotonic and cyclic loading, respectively; moreover, the deformability ratio evaluated on the basis of the rotation angles corresponding to the yielding and maximum moments of the connections was increased by 94%. Locally cross-laminated connections were also found to dissipate more energy (25%) than unreinforced connections. A comparison of the cross-laminated technique with self-tapping screws indicated that the respective reinforcing effects were comparable with that of the screws being slightly higher. Because the locally cross-laminated technique is readily incorporated into the production of cross-laminated timber products, it may have broad applications in heavy timber-bolted connections. [ABSTRACT FROM AUTHOR]

This article studies the possibility of using market available glued-laminated timber (GLT) based on melamine-urea-formaldehyde (MUF) adhesives as an alternative to traditional solid timber sleepers. The study comprised an examination of the effect of creosote treatment on the short-term and durability after accelerated aging of the glue lines (delamination and shear strength) and the potential for full sapwood penetration by the creosote. Creosote treatment showed a negative effect on shear strength and delamination, more severe in the nonstructural than the structural GLT specimens tested. Full penetration of creosote into the sapwood was not achieved. GLT elements based on MUF adhesives can be considered an alternative to solid wood sleepers if specific grading of lamellas, proper treatment schedule, and highly controlled factory production are implemented. [ABSTRACT FROM AUTHOR]