Showing papers in "European Journal of Wood and Wood Products in 2016"
TL;DR: In this article, the authors provide a state-of-the-art report on some selected topics related to CLT, in particular production and technology, characteristic material properties, design and connections.
Abstract: Cross laminated timber (CLT) has become a well-known engineered timber product of global interest. The orthogonal, laminar structure allows its application as a full-size wall and floor element as well as a linear timber member, able to bear loads in- and out-of-plane. This article provides a state-of-the-art report on some selected topics related to CLT, in particular production and technology, characteristic material properties, design and connections. Making use of general information concerning the product’s development and global market, the state of knowledge is briefly outlined, including the newest findings and related references for background information. In view of ongoing global activities, a significant rise in production volume within the next decade is expected. Prerequisites for the establishment of a solid timber construction system using CLT are (1) standards comprising the product, testing and design, (2) harmonized load-bearing models for calculating CLT properties based on the properties of the base material board, enabling relatively fast use of local timber species and qualities, and (3) the development of CLT adequate connection systems for economic assembling and an increasing degree of utilization regarding the load-bearing potential of CLT elements in the joints. The establishment of a worldwide harmonized package of standards is recommended as this would broaden the fields of application for timber engineering and strengthen CLT in competition with solid-mineral based building materials.
427 citations
TL;DR: In this article, a short overview of the use of TCCs, the relevant regulatory framework, and several case studies are presented to give a worldwide perspective from regions where TCC systems are being used.
Abstract: Timber-concrete-composite (TCC) systems have increasingly been used in recent decades. One of the main reasons for this development is related to applications that could not be built with timber alone, but that become possible with a TCC solution. This paper first gives a short overview of the use of TCCs, the relevant regulatory framework, and then presents several case studies of TCC applications. The perspectives and examples are from Europe, North America and Oceania to give a worldwide perspective from regions where TCC systems are being used. The structural systems presented in the case studies include bridges and floors in public buildings. For each project, details of the application are presented and the way each one contributed to extend the use of timber in construction.
100 citations
TL;DR: Treet as mentioned in this paper is a 14-storey timber apartment building in Norway currently under construction, which consists of load-carrying glulam trusses and two intermediate strengthened levels.
Abstract: “Treet” is a 14-storey timber apartment building in Norway currently under construction. Ground works started in April 2014, and the residents can
move in autumn of 2015. The building will be one of the tallest timber buildings in the world. The building consists of load-carrying glulam trusses and two intermediate strengthened levels. Prefabricated building modules are stacked on top of the concrete garage and on top of the strengthened levels. There is CLT in the elevator shaft, internal walls and balconies. But, CLT is not a part of the main load bearing system. Glass and metal sheeting protect the structural timber from rain and sun. The paper presents the design of the building as well as many of the investigations, considerations and discussions which took place during the design process. Finally some of the design verifications are presented.
80 citations
TL;DR: In this article, the physical and mechanical properties of particleboard made from bamboo using citric acid as natural binder were investigated, and the results showed that addition of Citric acid could significantly improve the dimensional stability and physical properties of the boards, while bamboo species did not significantly affect the properties of boards.
Abstract: Utilization of citric acid as natural
binder for non-wood composite is still limited. Therefore, this study investigated the physical and mechanical properties of particleboard made from bamboo using citric acid as natural binder. Three bamboo particles, i.e. petung bamboo (Dendrocalamus asper), wulung bamboo (Gigantochloa atroviolacea), and apus bamboo (Gigantochloa apus) were used as raw materials in this research. Citric acid contents were set at 0, 15 and 30 wt.% based on air-dried particles. Two classifications of petung bamboo particle sizes (coarse and fine particles) were used in this research. The particleboards were also made as single layer and three layer boards with variation of layer compositions. The results showed that addition of citric acid could significantly improve the dimensional stability and mechanical properties of the boards, while bamboo species did not significantly affect the properties of boards. Fine particles provided higher internal bond strength of the particleboard than coarse particles, due to bigger contact area among fine particles. Single layer particleboard provided higher internal bond strength compared to the three layer ones. The properties of citric acid-bonded bamboo particleboard in this research could meet the requirements of the Japanese Industrial Standard for particleboard (A 5908). Fourier transform infrared analysis indicated that the peak at around 1734 cm−1 was hardly recognized in binderless board, however it clearly appeared in citric acid-bonded particleboards. As a result of reaction between citric acid and bamboo, good properties of particleboards could be obtained.
65 citations
TL;DR: In this paper, an overview of traditional and recent design approaches for floor vibrations is given, with those approaches intended to allow engineers to implement design strategies that produce floors that perform acceptably under service conditions.
Abstract: Vibration serviceability of timber floors is becoming increasingly relevant due to their increased long-span applications in pure timber and hybrid structures. As a serviceability limit state, the check of acceptable floor vibrations is part of some current timber design standards. However, a universal agreement on acceptance levels and design procedures has not been achieved. This paper gives an overview of traditional and recent design approaches for floor vibrations, with those approaches intended to allow engineers to implement design strategies that produce floors that perform acceptably under service conditions. The subsequent discussion does not catalogue all relevant technical literature, information in design manuals and aids, nor list all relevant design code rules related to vibration serviceability of timber floors. Instead what is written is intended to convey and critique the state of background knowledge, design recommendation and code rules using illustrative examples from the literature. The objective is to contribute to resolution of debate about control of floor response characteristics by engineering design methods.
64 citations
TL;DR: In this article, a review on cork as a natural, renewable and sustainable construction raw material is presented, focusing on the application of cork in buildings and infrastructures, such as insulation, wear-resistance and durability.
Abstract: This review focuses on cork as a natural, renewable and sustainable construction raw-material. Cork has an unusual combination of properties making it suitable for application in buildings and infrastructures, for example insulation, wear-resistance and durability. The material properties combined with a favourable ecological footprint allow designers, architects and engineers to meet some of the Green Building demands. A summary on cork production, structure, chemistry and properties was made. The processing into cork-based products, for example cork agglomerates and composites, is detailed as well as their properties and applications in construction. The aptitude of cork-based products for compliance with sustainability and energy efficiency criteria is also addressed.
61 citations
TL;DR: In this paper, different ratios of wood powder were used as a component in adhesive mixtures for 3D printing, and the optimum mixture was determined by measuring the corresponding extrusion forces.
Abstract: In recent years there has been much development in the field of additive manufacturing technologies, but only a few attempts have been made to use natural materials like wood for 3D printing. In this research different ratios of wood powder were used as a component in adhesive mixtures for 3D printing. Polyvinyl acetate and urea–formaldehyde adhesives were used as binders, and the optimum mixture was determined by measuring the corresponding extrusion forces. Simple blocks were 3D printed and the bending properties of these blocks were investigated. The bending strength depended on the amount of wood powder in the mixture and on the type of adhesive.
58 citations
TL;DR: In this article, the normative background to strength grading in Europe is discussed, addressing important aspects that are commonly misunderstood by structural engineers and timber researchers and highlighting changes that are being made to the standards to: incorporate requirements of the construction products regulations; add improvements to the system to accommodate the latest knowledge and technology; and widen the application of the standards.
Abstract: This paper is a concise explanation of the normative background to strength grading in Europe, addressing important aspects that are commonly misunderstood by structural engineers and timber researchers. It also highlights changes that are being made to the standards to: incorporate requirements of the construction products regulations; add improvements to the system to accommodate the latest knowledge and technology; and widen the application of the standards. Where designs need to be optimised, there is an opportunity to use the system more intelligently, in combination with the latest technology, to better fit design values to the true properties of the timber resource. This can bring a design enhancement equivalent to effort improving other aspects of the structure, such as connectors and reinforcement. Parallel to this, researchers working on other aspects of structural improvement need to understand what grades really mean in respect of the properties of the timber, in order to correctly analyse the results of testing. It is also useful to know how techniques used in grading can assist with material properties characterisation for research. The amount of destructive testing involved in establishing machine grading settings and visual grading assignments presents a barrier to greater use of local timber, and diversification of commercial species, so it is important that any researcher assessing the properties of such species should consider, from the outset, doing the research in a way that can contribute to a grading dataset at a later date. This paper provides an overview of what is required for this.
56 citations
TL;DR: In this article, the authors used rosin to improve the physical and mechanical properties of fast growing poplar wood using the impregnation method, where rosin was dissolved in ethanol with different concentrations and the wood was impregnated with the solutions obtained.
Abstract: Rosin was used to improve the physical and mechanical properties of fast-growing poplar wood using the impregnation method. The rosin was dissolved in ethanol with different concentrations and the wood was impregnated with the solutions obtained. The weight percent gain, density, equilibrium moisture content (EMC), anti-swelling efficiency (ASE), and mechanical properties of the treated wood were measured in detail. The crystalline structure, morphology, rosin distribution, and dynamic wettability were also evaluated. Results showed that the density of the wood increased from 0.34 to 0.44 g/cm3 after the treatment with 20 % rosin solution. When the rosin content increased by 5, 10, 15 and 20 %, the ASE after 5 days water immersion increased to 15.6, 20.6, 30.3 and 36.0 % and EMC reduced by 17.8, 26.5, 36.2 and 42.7 %, respectively. Particularly, the modulus of rupture, modulus of elasticity, and compression strength of the 20 % rosin impregnated wood increased by 12.8, 18.9, 31.6 %, respectively. In addition, the dynamic wettability of wood was significantly changed by the rosin treatment. The rosin within wood could occupy the wood lumens, cell corners, and middle lamella, and partly penetrated wood cell walls, which was revealed by field emission scanning electron microscope and confocal laser scanning microscope.
54 citations
TL;DR: In this paper, nine European softwood and hardwood species (ash, beech, birch, hornbeam, larch, oak, poplar, black locust and spruce) were assessed for their ability to be bonded with three different commercial adhesive systems.
Abstract: Due to the increasing interest in applying a wider range of wood species for structural purposes, nine European softwood and hardwood species (ash, beech, birch, hornbeam, larch, oak, poplar, black locust and spruce) were assessed for their ability to be bonded with three different commercial adhesive systems (melamine–urea–formaldehyde, one-component polyurethane and phenol–resorcinol–formaldehyde). Tensile shear strength and delamination tests were conducted according to European standards, for all tests including the corresponding wood species as adhesive joints and as a solid wood reference. When tested in dry condition, the threshold of solid wood tensile shear strength was reached by all species–adhesive combinations. By contrast, testing in wet condition revealed distinct performance reductions for certain combinations. This trend was confirmed by delamination testing. Overall, the results indicate that extrapolation of test results achieved with a specific wood species (as recommended in the current standard for lap-joint tests) towards other species is highly problematic and has to be done with caution.
54 citations
TL;DR: In this article, a review of glued-in rods and plates illustrates that high stiffness and high ductility can be achieved using a combination of steel and adhesive, combined with self-tapping screws, an adhesive layer between joist and beam, and a combined combination of both: the results demonstrated that all three types of creating a hybrid joint increased the joint stiffness.
Abstract: The performance and efficiency of any structure depend on the connections that join their components; as such they constitute the most critical component. This is also true for timber structures, where joining of components is mostly achieved by means of mechanical interlocking, metal fasteners, adhesively bonding, or less common, a hybrid solution between two or more of these means. This paper gives an overview of hybrid jointing approaches: glued-in rods and plates, and a novel grouting technology with concrete-type adhesives, and hybrid carpentry type joints. The review of glued-in rods and plates illustrates that high stiffness and high ductility can be achieved using a combination of steel and adhesive. The grouted joints were investigated experimentally and numerically and the good agreement between them validated the design process and allows dimensioning. The carpentry type joints were combined with self-tapping screws, an adhesive layer between joist and beam, and a combination of both: the results demonstrated that all three types of creating a hybrid joint increased the joint stiffness. All these examples of best practise timber engineering show the potential that connections can be more efficient by improving established solutions through hybridization.
TL;DR: In this paper, the degradation of beech wood during a thermal modification process in a high-pressure reactor system using steam as medium was investigated, and it was found that wood degradation was predominantly determined by the maximum pressure, rather than the peak temperature applied.
Abstract: The degradation of beech wood during a thermal modification process in a high-pressure reactor system using steam as medium was investigated. The wood was modified at different peak temperatures (150–180 °C), peak durations (1–6 h) and maximum water vapor pressures (0.14–0.79 MPa), while wood mass loss and wood moisture content as well as soluble degradation products were analyzed. Wood degradation was found to be predominantly determined by the maximum pressure, rather than the peak temperature applied. However, accumulation of degradation products, i.e., carbohydrates and furfural, in wood modified at elevated pressure had to be considered when using mass loss as a marker for wood degradation. Mass loss and mass loss rate increased with the maximum pressure until reaching saturation at mass losses above 20 %, due to the limited amount of amorphous carbohydrates within the wood. Several factors have been discussed with regard to their impact on accelerated degradation reactions at elevated water vapor pressure, such as a better heat transfer in a compressed gas atmosphere, reduced evaporative cooling, the accumulation of organic acids as well as the presence of water in the wood during the process. However, none of these individual factors were completely consistent with the observed mass loss progression, which leads to the conclusion that the impact of elevated water vapor pressure, rather, is a combination of several factors that apply simultaneously. The application of elevated pressure might enable an effective process technique to generate sufficient wood degradation to upgrade dimensional stability and biological durability of wood at a low temperature range.
TL;DR: In this article, the state of the art of FRP reinforcement for wood structural members is discussed and various methods are discussed, including passive reinforcement, slack reinforcement and pre-stressing in FRP materials.
Abstract: Using bonded fibre-reinforced polymer (FRP) laminates for strengthening wooden structural members has been shown to be an effective and economical method. In this paper, properties of suitable FRP materials, adhesives and two ways of strengthening beams exposed to bending moment are presented. Passive or slack reinforcement is one way of strengthening. The most effective way of such a strengthening was to place reinforcement laminates on both tension and compression side of the beam. However, the FRP material is only partially utilised. The second way is to apply pre-stressing in FRP materials prior to bonding to tension side of flexural members and this way was shown to provide the most effective utilisation of these materials. The state of the art of such a strengthening and various methods are discussed. Increasing the load-bearing capacity, introducing a pre-cambering effect and thus improving serviceability which often governs the design and reducing the amount of FRP reinforcement needed are some of the main advantages. A recent development on how to avoid the requirement for anchoring the laminates at the end of the beams to avoid premature debonding is shown, and the advantage of such a system is described.
TL;DR: In this article, the biological resistance of Scots pine (Pinus sylvestris L.) wood impregnated with nano-sized zinc oxide and zinc borate against the fungi Daedalea quercina, Poria placenta and Serpula lacrymans was evaluated.
Abstract: In this work, the biological resistance of Scots pine (Pinus sylvestris L.) wood impregnated with nano-sized zinc oxide and zinc borate against the fungi Daedalea quercina, Poria placenta and Serpula lacrymans was evaluated. It can be concluded that nano-sized zinc oxide inhibited the biological degradation of pine wood against Serpula lacrymans, while it was ineffective against the brown-rot fungus Poria placenta. Pine wood treated with nano-sized zinc borate exhibited higher biological resistance against the fungi Serpula lacrymans and Poria placenta.
TL;DR: In this paper, the flexural properties in the longitudinal direction for natural and thermo-hydro-mechanically densified Moso bamboo (Phyllostachys pubescens Mazel) culm wall material are measured.
Abstract: The flexural properties in the longitudinal direction for natural and thermo-hydro-mechanically densified Moso bamboo (Phyllostachys pubescens Mazel) culm wall material are measured. The modulus of elasticity (MOE) and modulus of rupture (MOR) increase with densification, but at the same density, the natural material is stiffer and stronger than the densified material. This observation is primarily attributed to bamboo’s heterogeneous structure and the role of the parenchyma in densification. The MOE and MOR of both the natural and densified bamboo appear linearly related to density. Simple models are developed to predict the flexural properties of natural bamboo. The structure of the densified bamboo is modelled, assuming no densification of bamboo fibers, and the flexural properties of densified bamboo are then predicted using this structure and the same cell wall properties of that of the natural material modelling. The results are then compared with those for two analogous structural bamboo products: Moso bamboo glulam and scrimber.
TL;DR: In this article, the effect of applying fumed silica with nanoscopic-size particles as a filling material for melamine-urea-phenol-formaldehyde (MUPF) resin in the process of manufacturing water-resistant plywood was examined.
Abstract: This work examines the effect of applying fumed silica with nanoscopic-size particles as a filling material for melamine-urea-phenol-formaldehyde (MUPF) resin in the process of manufacturing water-resistant plywood. Moreover, this paper investigates the possibility of reducing the amount of MUPF resin mixture used in the process of gluing veneer sheets. Based on the investigations into the reactivity, viscosity and durability of MUPF resin mixture containing various amounts of nanofiller, it was found that the optimum amount of silica that can make the resin suitable for gluing sheets of veneer amounts to 2 PBW per 100 PBW of MUPF resin. The gluing properties for thus mixed resin were determined by measuring the contact angle and determining the parameters of its derivatives, which are an additional criterion for evaluating the gluing properties. The thermal stability was tested with simultaneous use of TG–DSC analysis. The experimental plywood manufactured using optimal nano-SiO2 was tested in terms of bond quality and mechanical properties according to appropriate standards. The investigations prove that it is possible to apply fumed silica as a filling material for the resin in the process of manufacturing water-resistant plywood. Introducing the above-mentioned amount of fumed silica into the resin makes it possible to increase the activation energy of the cross-linking process of MUPF resin and to optimize the process of gluing the sheets of veneer. Moreover, it is also possible to produce plywood of the required water-resistance with the amount of adhesive mixture reduced by 30 %.
TL;DR: In this article, the antifungal activity of extractive compounds obtained with fexIKA accelerate extraction process was evaluated for European beech (Fagus sylvatica L.) samples used for impregnation and as reference samples.
Abstract: This study aims at evaluating the antifungal activity of extractive compounds obtained with fexIKA accelerate extraction process. Black locust (Robinia pseudoacacia L.) and African padauk (Pterocarpus soyauxii Taub.) heartwood as well as black locust bark were used as the source material for investigation. After grinding, extraction, impregnation and rapid durability test, the efficiency of extractive compounds was assessed by the mass loss of European beech (Fagus sylvatica L.) samples used for impregnation and as reference samples. Results showed that the extractive compounds obtained from black locust heartwood were able to increase the native durability of European beech from class 5 (i.e. not durable with an average mass loss of 43.6 %) to class 3 (i.e. moderately durable with an average mass loss of 12.7 %), rendering this study’s finding encouraging for the future use of extractive compounds as protective agents for wood.
TL;DR: In this paper, two melamine urea formaldehyde (MUF) resins, two polyurethanes (PUR), one emulsion polymer isocyanate and one phenol resorcinol formaldehyde resin were taken for bonding.
Abstract: Delamination resistance and tensile shear strength (TSS) are essential for load-bearing timber structures. Thus these two factors were investigated on industrially bonded ash wood (Fraxinus excelsior L.) to check for the suitability of adhesively bonded ash wood as a building material. Two melamine urea formaldehyde (MUF) resins, two polyurethanes (PUR), one emulsion polymer isocyanate and one phenol resorcinol formaldehyde resin were taken for bonding. Face milled and planed surface series were made to highlight potential differences. For PUR, an additional series with dimethylformamide primed surfaces was also made. The influence of the mixing ratio and the closed assembly time were analysed for one MUF system. The samples for the TSS were tested in dry and wet conditions. 80 % of the tested series met the standard requirements (EN 15425; EN 301) in dry condition, whereas only 30% passed in wet condition. None of the adhesives tested were able to pass the delamination test. No distinct influence of the different parameters studied is notable for most of the adhesive systems, only extended CATs and lower MRs seem to improve the bond quality of MUF. In addition, chemical analyses were performed to find evidence for the poor bonding performance. It was found that acidic extractives, fatty acid content and pH of ash fell within the range of beech and spruce wood, with only formic acid being an exception with an amount four times higher than the other two wood species.
TL;DR: In this paper, the effect of substitution of the formaldehyde by furfural in urea formaldehyde (UF) resins was investigated and its effect on formaldehyde emission and physical-mechanical properties of particleboard panels produced from poplar wood was examined.
Abstract: To diminish the formaldehyde emission, replacement of the formaldehyde by furfural in urea formaldehyde (UF) resin was investigated and its effect on formaldehyde emission and physical–mechanical properties of particleboard panels produced from poplar wood was examined. Resin type: Industrial UF, Laboratory UF, UF-Furfural (in 25 and 50 % replacement levels), and two press temperatures including 170 and 180 °C were considered as variables. Results indicated that formaldehyde emission and modulus of rupture (MOR) of panels reduced thereby replacing the formaldehyde by furfural in UF resin. Internal bonding (IB) of panels made using 50 % replacement-modified resin was superior to others. Water absorption of panels decreased after 2- and 24-h immersion of samples with modified resins, as opposed to thickness swelling. The minimum thickness swelling was observed in panels made by Industrial UF resin. It is noteworthy that formaldehyde emission enhanced by increasing the temperature from 170 to 180 °C, and also all physical–mechanical characteristics developed at 180 °C temperature.
TL;DR: In this article, the behaviour of screwed connections (timber/large gap/timber) is modelled using an orthotropic material, cohesive surface, Hill criterion and a fictitious material that wraps the screw and models a complex medium where steel and wood interact.
Abstract: Since the 80’s, Johanssen’s Yield Theory has been adapted to fit new design practices: fastening of timber elements with a layer of insulation (or gap) between the elements or fastening with inclined fasteners. However no rules exist for connections with large gaps (up to 500 mm) and inclined fasteners. The behaviour of screwed connections (timber/large gap/timber) is modelled using an orthotropic material, cohesive surface, Hill criterion and a fictitious material that wraps the screw and models a complex medium where steel and wood interact. The calibrated FE model is finally compared to experimental results.
TL;DR: In this article, the bending behavior of Cross Laminated Timber panels is investigated by means of the linear elastic exact solution from Pagano (1970, 1969), the resulting stresses are the input for a wood failure criterion, which can point out the first-crack load and the respective dominant failure mode.
Abstract: In the present paper, the bending behavior of Cross Laminated Timber panels is investigated by means of the linear elastic exact solution from Pagano (1970, 1969). The resulting stresses are the input for a wood failure criterion, which can point out the first-crack load and the respective dominant failure mode. Heterogeneous layers are modeled as equivalent and homogeneous layers. This simplified and deterministic modeling gives results in good agreement with a reference experimental test. A comparison is made with respect to the panel’s global stiffness and failure stages within the apparent elastic stage. Finally, parameter studies are carried out, in order to quantify CLT limitations and advantages. The effect of varying properties such as the panel’s slenderness, orientation of transverse layers and number of layers for a fixed total thickness are investigated.
TL;DR: Physico-chemical characterization of six commercially important Indian bamboo species has been performed, finding that B. pallida, Bangalore and D. strictus, Gurgaon have the lowest and highest lignin content and antifungal decay resistance, respectively.
Abstract: Physico-chemical characterization of six commercially important Indian bamboo species has been performed. The maximum starch content was found in B. vulgaris, highest hot water soluble constituents noticed in B. pallida, Bangalore, while lowest content of these soluble constituents was observed in B. tulda, Bihar. All the bamboo species have alkali solubility ranging from 26.1 to 28.3 %. B. pallida, Bangalore and D. strictus, Gurgaon have the lowest and highest lignin content and antifungal decay resistance, respectively. Maximum and minimum ligno-cellulose content was found to be in B. arundinacea, Allahabad, and B. tulda, Bihar bamboo species.
TL;DR: In this paper, the authors investigated the effect of borax impregnation of polyglycerolmethacrylate (PGMA) before thermal treatment on the performance of thermally modified wood in ground contact.
Abstract: Environmental pressures in France and in most European countries during the last decade have considerably changed the practises for wood protection. In this context, legislation and regulations, among which the Biocidal Products Directive (BPD) and Biocidal Products Regulations (BPR), are more and more constraining leading to the development of more environmentally acceptable preservation formulations and to an increasing interest in non-biocidal alternatives like thermal or chemical modifications. Wood heat treatment has been one of the most investigated alternative methods during the last years. However, even if some of the wood properties, like its decay resistance or and dimensional stability, are improved, the overall durability of the material is not sufficient to envisage use class 3 and 4 applications, where the wood is in direct contact with soil and termites. Impregnation of borax associated to polyglycerolmethacrylate (PGMA) before thermal treatment could be an attractive alternative to improve the performance of thermally modified wood in ground contact and especially its resistance to termites taking advantage of thermal treatment to initiate polymerization of PGMA within the wood structure to limit boron mobility. Thermo-modification with or without combination of boron impregnation and PGMA improved the durability of all wood samples. Thermal treatment alone or after boron impregnation and leaching was unable to effectively protect wood blocks against termites after leaching, while bocks treated with boron and PGMA were shown to be fully resistant to termites. More surprisingly, association of thermal treatment and PGMA impregnation without boron impregnation also produced protection against termite attack. Such treatments may be valuable alternatives to extend the scope of utilization of thermally modified wood in outdoor conditions.
TL;DR: In this article, the performance of different timber species Norway spruce (Picea abies Karst), European ash (Fraxinus excelsior L.) and European beech (Fagus silvatica L.) was evaluated based on pull-compression tests of glued-in rods.
Abstract: Ongoing development of timber and timber products made from European hardwoods like ash and beech influences the selection of acceptable methods for connecting these elements and thus demands validation and application of current design methods for softwood and glulam. For the last 20 years, despite many national and international research projects and practical applications of glued-in rods in timber structures, there is still no universal standard with respect to their design. The use of adhesives available for bonding rods and timber is limited to softwood. This work shows the performance of different timber species Norway spruce (Picea abies Karst.), European ash (Fraxinus excelsior L.) and European beech (Fagus silvatica L.) and engineered timber products (laminated veneer lumber made of Norway spruce and European beech) based on comprehensive pull-compression tests of glued-in rods. For characterizing the elastic and elastic-plastic behavior, failure loads as well as stiffness and ductility were considered whereby the rod diameter and anchorage length were maintained constant. The aim of the research was to show that glued-in rods cannot only be used in softwoods and glulam members but also in hardwoods and in wood-based products such as LVL.
TL;DR: Physical and mechanical properties of compreg laminated bamboo/wood hybrid using phenolic-resin-treated strips as core layer were investigated in this article, where compreg laminates made from treated core layer revealed better properties than the untreated control samples.
Abstract: Physical and mechanical properties of compreg laminated bamboo/wood hybrid using phenolic-resin-treated strips as core layer were investigated. Compreg laminates made from treated core layer revealed better properties than the untreated control samples. Compreg laminated wood showed lower properties compared to compreg laminated bamboo and bamboo/wood hybrid. Assembly orientation exerted great influence on the properties as parallel laminated samples showed better strength and dimensional stability.
TL;DR: In this paper, the bending strength and stiffness of loblolly pine lumber from intensively managed stands located on the Georgia Lower Coastal Plain were evaluated using four-point bending according to ASTM International standards and the results point to the current mean values being reasonably comparable to the previous design values and currently meeting or exceeding the current design values for visually graded southern pine lumber.
Abstract: Loblolly pine is increasingly grown on intensively managed plantation forests that yield excellent growth; however, lumber cut from these trees often contains a large percentage of juvenile wood which negatively impacts strength and stiffness. Because of changing forest management and mill practices the design values for visually graded southern pine were updated in 2013 to more accurately account for the material properties available in commerce. This study was undertaken to assess the bending strength and stiffness of loblolly pine lumber from intensively managed stands located on the Georgia Lower Coastal Plain. Eight hundred and forty-one pieces of lumber sawn from 93 trees age 24–33 years were tested in four-point bending according to ASTM International standards. The No. 1 grade MOE15 (11.9 GPa) was greater than the current (11.0 GPa) design value and comparable to the previous (11.7 GPa) design value. The No. 2 grade MOE15 (10.6 GPa) was greater than the current (9.7 GPa) design value but slightly less than the previous (11.0 GPa) design values. The No. 3 grade MOE15 (9.3 GPa) was between the current (9.0 GPa) design value and the previous (9.7 GPa) design value. Altogether, these results point to the MOE15 mean values being reasonably comparable to the previous design values and currently meeting or exceeding the current design values for visually graded southern pine lumber.
TL;DR: In this paper, a series of pull compression tests with different angles to the grain have been performed applying both polyurethane and epoxy resin as adhesives, and no influence of the grain angle on the load carrying capacity could be found.
Abstract: Beech laminated veneer lumber is a new engineered wood product with superior mechanical properties and high density. In order to take advantage of this superior mechanical performance in the case of connections with glued-in rods a series of pull compression tests with different angles to the grain have been performed applying both polyurethane and epoxy resin as adhesives. No influence of the grain angle on the load carrying capacity could be found. In addition, a survey on design rules and their acceptance in practice has been carried out, showing a clear need for further standardization.
TL;DR: In this article, the barriers to internationalization for wood processing and wood trading firms in Slovakia are identified and the influence of previous experience with international business and firm size on perceptions of barriers to enter foreign markets was examined.
Abstract: In this study, barriers to internationalization for wood processing and wood trading firms in Slovakia are identified. Specifically, the perceptions of 62 Slovak firms were examined regarding entry into European Union markets. In addition to competitive issues, the influence of previous experience with international business and firm size on perceptions of barriers to enter foreign markets was examined. Results suggest that foreign competition is considered to be the most significant barrier due to a low level of innovation from domestic companies. In addition, the need to invest in promotional activities and limited access to capital are also significant barriers to entry into EU markets. Firm size was not found to be correlated with market barriers and no significant differences in perception of barriers was found between firm owners and managers.
TL;DR: In this article, a finite element inverse analysis procedure was developed in such a way that anisotropy of the thermal conductivity was accounted for, and it was recommended to use both in-plane and transverse thermal conductivities for modeling heat transfer.
Abstract: Accuracy and effectiveness of predicting the heat transfer in wood-based panels is increasingly important for describing their behavior, especially for varying environmental conditions. To model the heat transfer in wood-based panels it is essential to input credible data on their thermal properties. Therefore, proper estimation of the specific heat and thermal conductivity is fundamental. A finite element inverse analysis procedure was developed. The procedure was designed in such a way that anisotropy of the thermal conductivity was accounted for. For all analyzed wood-based panels, in-plane thermal conductivity was significantly higher compared to the transverse one, and it was recommended to consider the anisotropy, and to use both in-plane and transverse thermal conductivity for modeling heat transfer. The effect of temperature on thermal conductivity was not clearly manifested. The thermal conductivity values were decreasing or increasing with temperature. In some cases this influence was practically insignificant (i.e. OSB), while for low density fiberboard the effect of temperature on thermal conductivity was the highest. The identification procedure was validated and its credibility was assessed. It was shown that data on thermal properties available in the literature should not be recommended to model the heat transfer.
TL;DR: In this paper, a multi-sensor system is used to reconstruct the 3D surface topography and a camera records the grayscale image of the same surface while the sample is rotated around a central axis.
Abstract: The quality evaluation of a wooden surface machined by peripheral milling can be achieved by means of the visual assessment or by surface roughness measurement. The method defined in this paper is a novel alternative to the state-of-the-art material machine-ability evaluation providing objective results acquired by an automatic system. Critical machining conditions and surface defects are stimulated by a purposely-designed circular sample. The approach proposed bases on a multi-sensor technology where a laser triangulation system reconstructs the 3D surface topography and a camera records the grayscale image of the same surface while the sample is rotated around a central axis. The dedicated software allows automated surface reconstruction, quality assessment and the detection of specific defects. The method is rapid and allows an easy comparison of different cutting conditions intended as a tool to rapidly determine optimal solutions.