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Nailplates are widely used in domestic and low-rise residential housing markets and have begun forming part of mid-rise developments. There is however a concern about nailplates backing out which has been observed in a variety of conditions. In-service backouts in excess of 2 mm have been recorded and can result in up to a 50 % reduction in joint performance. The amount of backout varies significantly from roof space to roof space and the physical phenomena leading to backout and their exact relationship to the climatic conditions are largely unknown. This paper experimentally investigates the time dependent backout mechanisms and develops a numerical model to predict the range of backouts that will be expected from a set of climatic conditions that the nailplates would be exposed to. Specifically, this paper initially investigates the backout of single nails, representative of nailplate teeth, by pressing the nails into pieces of timber and subjecting the samples to cyclic climatic conditions. The moisture driven backout of the nails was monitored in real-time using Digital Image Correlation for 48 days. Backouts of between 0.08 and 0.26 mm were observed. Results showed that during the drying phase, the timber surface tended to slide along the surface of the nail. A similar phenomenon was observed during the wetting phase but to a lower extent. This consequently led to a ratcheting mechanism that caused the nail to backout from the timber. A numerical model is then proposed to predict and replicate the time dependent backout behaviour of the nailplate tooth based on heat and mass transfer algorithm TransPore and Finite Element Software ABAQUS. The model was validated against the experimental results based on the timber properties and climatic conditions that the timber was exposed to. The model was able to accurately predict the time-dependent backout of the nails. To illustrate the application of the model, the expected nailplate backout for two different Australian roof spaces was investigated. A variety of parameters was investigated including the length and position of the tooth. It was found that longer teeth experienced higher rates of backout and significant variations in backout were encountered whether the tooth is closer to the edge or the middle of the timber.

The compaction behavior of cotton stalk particle mats, temperature profile inside the particle mats, and influence of surface particle size were studied relative to the properties of three-layered cotton stalk particleboards. Modulus of rupture (MOR), modulus of elasticity (MOE), internal bond, and thickness swelling were used as a measure for mechanical and physical performance. Two types of cotton stalk particleboard were manufactured. Results indicated that compression stiffness of the particle mat increased with increasing particle size; however, it decreased with increasing mat moisture content and temperature. At mat moisture contents of 12% and 18%, the plateau temperature at the centerline was not significantly different between boards having coarse and fine particles. However, the plateau time of boards with coarse particles was significantly lower than that of boards with fine particles. Additionally, thickness swelling of boards with a surface particle size of 2 mm was significantly lower than that of boards with surface particle size of 4 mm. Boards with a surface particle size of 2 mm had MOR and MOE values 15% and 10% higher, respectively, than boards with surface particle size of 4 mm. Internal bond decreased 6.5% with decreasing surface particle size from 4 mm to 2 mm.

Novel light timber sandwich panels (referred to as BCS panels herein) are manufactured by gluing plywood faces to bamboo core rings. The panels are tested in compression and in bonding shear (between bamboo and plywood). A finite element model is developed and validated against the experimental results, and is used to capture the responses of the BCS panels under axial and combined axial and bending actions. A lognormal distribution is used to represent the mechanical properties of plywood in the finite element analyses (FEA). Moreover, effect of different core configurations, face thickness, core layers and initial imperfection shapes on the axial compressive capacity of the panels are investigated. Where possible, results are compared against theoretical predictions. Current test results show that under axial compressive action, the ultimate capacity to weight ratio of the BCS panels are up to 27.3% higher than a conventional CLT panel of the same dimension. At large slenderness ratios, the proposed BCS panels have ultimate axial capacities close to the conventional CLT panels. Under combined axial and bending loading, the BCS panels outperform a CLT panel of similar size.

This paper experimentally evaluates the embedment strength of laminated veneer lumbers (LVL) and cross-banded laminated veneer lumbers (LVL-C) manufactured from blending spotted gum (Corymbia citriodora) or white cypress pine (Callitris glaucophylla) veneers with hoop pine (Araucaria cunninghamii) veneers. Nominal 3.0 mm thick veneers were rotary peeled from small diameter (less than 30 cm) native forest sourced spotted gum and white cypress pine logs, and plantation grown hoop pine logs. 12-ply × 1.2 m (long) × 0.9 m (wide) LVL and LVL-C panels were manufactured using ten different construction strategies by mixing (i) the number of veneers from each species, (ii) the modulus of elasticity of the veneers and (iii) the veneer orientations (cross-banding). A total of 672 embedment tests, using three different dowel diameters and four different load-to-grain orientation angles, were performed using the half-hole test method described in the ASTM D5764-97a. This paper (i) compares the proportional limit strength, 5%-offset embedment strength and maximum embedment strength across the different construction strategies adopted in the study, and (ii) discusses the results in terms of load-to-grain angle and dowel diameter. More importantly, the test results are also compared to the embedment strength prediction equations detailed in the Eurocode 5 to determine their suitability for mixed-species LVL and LVL-C products. Overall, the mixed-species LVL and LVL-C showed significantly higher 5%-offset embedment strengths than single-species commercial softwood LVL products. The effect of the cross-banded veneers on the embedment strength was not found to be significant. However, the LVL-C samples exhibited a highly ductile behaviour for all load-to-grain angles and dowel diameters when compared to the LVL samples. The experimentally determined 5%-offset and maximum embedment strengths for the mixed-species LVL were on average equal to and 7% higher than the predicted values given in Eurocode 5.

Nailplated timber trusses are widely used in residential housing. However, there is limited evidence of use or research on the application of nailplated trusses in exposed environments. It is common knowledge to the nailplated truss industry that weather-exposed trusses experience a phenomenon referred to as “nailplate backout”, where the nailplates separate from the timber surface due to the shrink-swell mechanism of the timber in response to its varying moisture content. This paper investigates the performance of innovative nailplated joints on: (1) stopping moisture-driven backout and (2) increasing the capacity of the joints, when compared to currently used joints, after exposure to severe moisture cycling. Three different experimental sets of joints were manufactured to achieve these outcomes, with Set 1 and Set 2 containing 100 splice and 100 butt joints while Set 3 had 40 splice and 40 butt joints. Sets 1 and 2 have a re-designed tooth profile where: (1) Set 1 combined a polyurethane adhesive with a modified nailplate tooth designed to allow the adhesive to penetrate the timber and (2) Set 2 implemented a hook in the middle of the nailplate teeth to grab the timber when the nailplate tries to separate from the timber, either from moisture induced backout or from loading. Polyurethane adhesive was also used in Set 3 but on an un-modified tooth profile. To evaluate the efficiency of the new nailplates, control joints with unmodified nailplates were manufactured for each set and tested. All joints were subjected to severe accelerated moisture cycles inside an air-driven kiln with the temperature being kept constant 70 °C and the relative humidity varied between 15 and 95%. The cycles consisted of a 7-h wetting and an 18-h drying period. For Sets 1 and 2, the tensile capacity of the joints was measured after 0, 3, 6, 9 and 12 moisture cycles, while for Set 3, it was only measured after 0 and 12 cycles. The backout was recorded after each moisture cycle for Sets 1 and 2 and after 12 cycles for Set 3. The average backout of Set 1 and Set 2 control joints after 12 severe cycles was 1.13 mm and 1.01 mm, respectively, while the addition of glue and a hook reduced the backout to 0.56 and 0.92 mm, respectively. In terms of capacity, the adhesive in Set 1 increased the capacity for the splice joints and butt joints by 43% and 13%, respectively. In Set 2, the hook only marginally increased the capacity of the splice joints by 13% and reduced the average butt joint capacity. Observations were made regarding the failure modes of the joints. The addition of the adhesive and hook to the nailplate teeth resulted in more joints failing due to the capacity of the timber rather than due to the nailplate separating from the timber during the tensile testing.

Recent research at the University of Queensland (UQ) has led to the development of a new type of structures called “Hybrid Fiber Reinforced Polymer (FRP)-Timber structures” (“HFT”). In HFT structures, FRP is combined with timber veneers to create high-performance, lightweight, easy-to-construct structural members. These HFT members take advantage (i) of the orthotropic properties of both, timber and FRP to orientate the fiber direction to produce optimal composite properties, and (ii) of the geometry of the cross sections to maximize the load bearing capacity for a given amount of material. While preliminary experimental work has revealed as such the effectiveness of HFT structural members, no work has been carried out so far to investigate the behavior of these HFT structures. Performance of these new HFT members relies significantly on the bond between FRP and timber. This paper presents the results of an experimental study aimed at selecting a suitable commercially available adhesive for glass fiber reinforced polymer (GFRP)-to-timber bonded joints. The experimental program included 393 single lap joint tests covering four different commercially available adhesives, two different curing temperatures, and two test methods (dry and moisture cycle tests). The test results revealed that both, polyurethane (PUR) and cross-linking polyvinyl acetate emulsion (PVAx) performed as the best under dry conditions, while PUR was shown to be superior to all other adhesives when subjected to moisture cycles. Epoxy and phenol resorcinol formaldehyde adhesive (PRF) commonly used in FRP structures and laminated timber structures, resp., were found to be less performing structural adhesives for HFT structures.

The main objective of this study was to investigate the key mechanical properties of cross-banded laminated veneer lumbers (LVL-C) manufactured from blending veneers recovered from sub-optimal native forest spotted gum and plantation hoop pine logs. The recovered veneers were separated into three grades based on their dynamic modulus of elasticity (MOE). Additionally, the spotted gum veneers were visually graded to evaluate whether a relationship exists between the MOE-based and visual grades. In total, six 12-ply reference LVL and six mixed-species 12-ply LVL-C panels were manufactured and analyzed for (i) flatwise and edgewise bending performance; (ii) bearing and tension strength perpendicular to the grain; and (iii) longitudinal-tangential shear strength. Little correlation was found between MOE-based and visual grades for the spotted gum veneers. The LVL- C showed flatwise and edgewise MOE up to 24% and 13% lower, respectively, than the reference mixed-species LVL. The flatwise and edgewise modulus of rupture were up to 39% and 19% lower, respectively. On average, the tensile and bearing strengths of the LVL-C were considerably higher than the hoop pine LVL and mixed-species LVL, with the former being approximately three times higher. The manufactured LVL-C showed markedly higher bending properties and tensile strengths than commercial LVL-C products.

This paper presents a methodology to optimise the manufacturing strategy of structural cross-banded laminated veneer lumbers (LVL-C) manufactured by mixing species. The methodology is illustrated by blending native-forest spotted gum (Corymbia citriodora) with plantation southern pine (Caribbean pine (Pinus caribaea var. hondurensis) and slash pine (Pinus elliottii var. elliottii)) veneers. The aim is to minimise the cost of a family of products (i.e. several types of product manufactured from the same veneered stock) using a maximum allowable number of hardwood veneers, and in which each product has different targeted stiffness and embedment strength. Genetic algorithm, which is widely used in the optimisation of structural products, was selected as the optimisation algorithm. The orientation of the veneers and veneer grades are considered as design variables. Results show that the developed algorithm was able to consistently converge to similar solutions for all investigated cases, demonstrating its robustness. For all cases, the “high” modulus of elasticity graded spotted gum and southern pine veneers were found to be predominant in the final products. LVL-C are found in cases with high targeted embedment strength. Finally, the obtained optimum construction strategies are validated against experimental results.

This paper presents the reliability analysis of Laminated Veneer Lumber (LVL) beams manufactured from veneers recovered from early to mid-rotation (juvenile) subtropical hardwood plantation logs, with plantations established either for sawn timber applications or pulpwood production. While these logs have a high number of natural defects (knots, gum veins, grain deviation, etc.), are considered of low quality and have little to no commercial value, they produce high strength Veneered Based Composite products, such as Plywood and LVL. Yet, the reliability of these products is unknown. In this paper, the relationship between the reliability index and the capacity factors, also referred to as “resistance factors”, used in design equations of such LVL beams in both edge and flat bending is investigated taking into account the load duration effects (damage accumulation). The relationship is presented for six different beam sizes, four grades and three hardwood species (Gympie messmate (Eucalyptus cloeziana), spotted gum (Corymbia citriodora) and southern blue gum (Eucalyptus globulus)) using the strength distribution of the beams recently quantified by the authors. Parametric studies on five main design load combinations stipulated in the Australian standard and three rates of damage accumulation, based on the data available in the literature, are conducted. Results show that the reliability index is highly sensitive to the damage accumulation rate and that the “Dead + Sustained and Extraordinary live loads” and “Dead + Wind + Sustained live loads” load combinations govern the choice of the capacity factor. Recommendations are made on the appropriate capacity factors to be used for various service categories of structures. The proposed capacity factors are found to be 5%–12% lower than the ones currently used in Australia for the LVL beams manufactured from mature softwood logs, as opposed to juvenile hardwood logs as in the proposed products.

The radial permeability (gas and liquid) of the hybrid pine (Pinus elliottii var. elliottii [PEE] × Pinus caribaea var. hondurensis [PCH]) was investigated for wood samples collected from 30 trees that were 19 years of age and represented various genotypes and stocking rates. The PEE × PCH hybrid is now a very important resource for the Australian forestry industry, producing logs used to manufacture a diverse array of wood products. The permeability of wood influences many important wood properties and industrial processes. For all data combined from all radial sampling positions, there was no significant effect of genotype and stocking rate on radial permeability. Both gas and liquid permeability increased from pith to bark positions within the tree. Conversely, resin content decreased from pith to bark positions. Gas and liquid permeability were significantly positively correlated, and a highly significant negative relationship was also found between permeability (gas and liquid) and resin content.

The original article was published with an erroneous affiliation details for co-author, David J. Lee. The correct affiliation for the author is Forest Industries Research Centre, University of the Sunshine Coast, Locked Bag 4, Maroochydore DC, QLD, 4558, Australia. The original article has been corrected

The flexural stiffness and ultimate load capacity of novel ultralight composite sandwich panels, made of plywood faces and bamboo or peeling cores are investigated herein. Modified Ritz method and sandwich beam theory formulations for composite sandwich panels with thick faces and thick/stiff cores are developed, and are used to find the bending stiffness of the panels in one-way and two-way bending. The ultimate capacity and failure modes of the panels are then predicted from nonlinear material and geometric finite element analyses (FEA). The numerical methods are validated against published experimental results of orthotropic composite sandwich panels. It is shown that at similar panel depths, the proposed composite timber panels can be as high as 15% stiffer and 40% lighter than the existing commercial cross-laminated timber (CLT) panels. Results of a parametric study on selected composite panels with different yield stresses in compression, show that panels with bamboo cores exhibit relatively more ductile behaviour compared to those with peeling cores. At the ultimate flexural capacity, the tensile face of the panels fails in tension parallel to the grain, while the compressive face almost reaches its yield capacity.

This paper quantifies the mechanical properties perpendicular to the grain and in shear of glued rotary peeled veneers, as would be encountered in veneer-based structural products (i.e. by including both the effects of hot pressing the veneers and the glue used during the manufacturing process), of three species recovered from juvenile (early to mid-rotation) subtropical hardwood plantation logs. This underutilised resource has currently little to no commercial value in Australia but proven potential to produce attractive veneer-based structural products. Determining these unknown properties is important as they constitute essential input data to ultimately predict the behaviour and design properties of veneer-based structural products in cost-effective numerical simulations. Two species planted for solid timber end-products (Gympie messmate—Eucalyptus cloeziana and spotted gum—Corymbia citriodora) and one species traditionally grown for pulpwood (southern blue gum—Eucalyptus globulus) are considered in the paper. The dynamic modulus of elasticity, compressive and tensile strengths perpendicular to the grain of veneer-based elements, each manufactured from single veneer sheets, were experimentally measured and are analysed herein. These properties are found to have no to weak correlation to the parent veneer sheet dynamic modulus of elasticity parallel to the grain, a value which is commonly measured in line to grade veneers. The shear modulus (in the longitudinal-tangential plane), also referred to as “modulus of rigidity”, through-the-thickness and rolling shear strengths were also experimentally measured, and the results are discussed in the paper. Little to no correlation to the veneer sheet dynamic modulus of elasticity parallel to the grain was found for these properties. Weibull distributions are fitted to all test results and presented to probabilistically consider the investigated properties in numerical simulations of veneer-based structural products.

Accurately determining the timber properties for products prior to cutting the tree is difficult. In this work we discuss a method for reconstructing a timber billet virtually, including internal features, after it has been peeled into a full veneer (ribbon). This reconstruction process is the first stage in developing a mathematical model for the variation in timber properties within a given tree. The reconstruction of internal timber features is typically achieved through the use of computed tomography (CT) scanning. However, this requires the use of equipment that may be cost-prohibitive. Here we discuss an approach that utilises more readily available equipment for timber processors, including a spindleless lathe and digital SLR camera. In comparison to conventional scanning methods, this reconstruction method based on a destructive process has the key advantage of delivering high-resolution colour images. This reconstruction serves two purposes. Firstly, we are able to generate three-dimensional visualisations of the timber billet, to uncover internal structures such as knots, defects, insect or fungi attack, discoloration, resin etc. Secondly, the reconstruction allows us to map timber properties measured on the veneer to their original location within the billet. This allows us to locally inform the mapping with wood properties and subsequently derive their distribution throughout the billet. From this information it is then possible to extract any part of the billet and obtain the appearance and wood properties of any processed products. To validate our reconstruction process we show that we can obtain reasonable agreement between our predicted billet modulus of elasticity and that measured on the original billet.

This paper presents the capacity and structural behaviour of hardwood veneer-based circular hollow sections (CHS) tested in bending, shear and compression. The sections were manufactured from early to mid-rotation (juvenile) Gympie messmate (Eucalyptus cloeziana) plantation thinned logs. In total twenty-one 167 mm Outside Diameter (OD) × 1.2 m long CHS were manufactured in seven sets of three nominally identical sections. Two different wall thicknesses were investigated to produce nine compact and twelve more slender cross-sections. The sections were also manufactured in three different structural grades. A sudden failure mode was observed in the compression zone of the slender sections tested in bending. In compression, the compact sections showed a ductile behaviour, while the slender sections showed a more brittle behaviour, with the sections bursting into longitudinal strips. While a relationship was observed between the bending and compressive capacities, and the structural grade, no such relationship was noticed for the shear capacity. Comparison to steel and concrete sections of similar outside diameter proved that the timber sections are the most efficient in terms of bending and compressive capacity to linear weight ratio. The timber sections fall behind their steel and concrete counterparts in terms of shear efficiency, however they still have enough shear capacity for representative structural applications.

This paper develops a mechanical model to accurately predict the strength of Laminated Veneer Lumber (LVL) beams, and illustrates its applications to numerically predict the strength distribution of LVL beams manufactured from veneers rotary peeled from early to mid-rotation subtropical hardwood plantation logs. This resource is not traditionally used in the manufacturing of commercialised LVL beams. In the first part of the paper, the model is described, calibrated against experimental results performed on 8-ply LVL beams and then verified against experimental results performed on 13-ply LVL beams. Results show that the model is able to accurately reproduce the experimental results, both on flat and edge bending, with an average prediction-to-experiment ratio of 1.0 and a relatively low coefficient of variation of 0.10. A sound prediction of the non-linear behaviour of the beams before failure was also observed. In the second part of the paper illustrating the applications of the model, the mechanical properties of veneers analysed by the authors in a previous work are used as input values in the numerical model to predict the strength of six commercially available LVL beam sizes, manufactured from early to mid-rotation subtropical Gympie messmate (Eucalyptus cloeziana), spotted gum (Corymbia citriodora) and southern blue gum (Eucalyptus globulus) plantation veneers. The design strength (5th percentile) of the beams, obtained by Monte Carlo simulations, is reported and found to range from 32.3 MPa to 97.2 MPa, depending on the quality of the veneers used and the beam size. The LVL beams have design strengths comparable to, and in some cases up to 2.5 times higher than commercially available softwood LVL beams, making them attractive structural products. The strength variability is also reported in the paper for developing probability-based limit state design criteria in future studies.

Veneer Based Composite (VBC) hollow sections are currently being developed in Australia as alternative products to sawn timber. However, due to the limited log length that peeling lathes can accommodate, solutions to manufacture long sections need to be investigated to create useable beams and columns. This paper experimentally assesses the bending capacity of three different concepts. Two concepts consist of manufacturing short sub-sections and connecting them together with (i) a sleeve inserted into the hollow-form and (ii) wrapping Fibre Reinforced Polymer (FRP) around the sub-sections at the connection. The third concept consists of manufacturing the sections in a continuous process, similar to LVL products. Three sets of four nominally identical circular hollow sections (1.2 m long, nominal 76.1 mm internal diameter and 15 mm wall thickness) were manufactured from Hoop pine (Araucaria cunninghamii) veneers. In each set, one section was used as the reference capacity, two sections were cut in half with the two halves being connected back together with either an aluminium sleeve or Glass Fibre Reinforced Polymer (GFRP). The last section had the veneers staggered and end joined, to mimic a continuous manufacturing process. Once cured the sections were then tested in four points bending. The sleeved sections were found to have the lowest bending capacity, while the GFRP and continuous sections reached more than 80% of the capacity of the reference sections. The latter two designs, therefore offer a potential solution for creating useable lengths of VBC hollow sections. Further research is required to refine and validate the design.

The facade, as the exterior cladding of a building, is an essential component which provides waterproofing, thermal isolation, light transparency and structural independence against environment actions. The vertical member, named mullion, is the dominant wind load-bearing structural member in this facade system. Even though aluminium is a durable material, the conventional aluminium frame is weak in thermal performance. On the other hand, timber frames are preferred by architects due to their aesthetic appearance and sustainability. Therefore, an innovative composite mullion was developed in this study using aluminium and timber to achieve the best features of both materials. An experimental study was also conducted to verify the structural performance of the composite mullion. Four-point bending tests were performed to investigate the bending behaviour of the newly developed product. The test results showed that the section moment capacities of the composite mullions are greater than the traditional aluminium mullions. © 2019 Taylor & Francis Group, London, UK.

This paper experimentally investigates the mechanical properties of rotary veneers peeled from small-diameter hardwood plantation logs, recovered from early to midrotation subtropical hardw...

International audience; A robust mathematical model was developed to simulate the heat and mass transfer process that evolves during vacuum-drying of four commercially important Australian native hardwood species. The hardwood species investigated were spotted gum (Corymbia citriodora), blackbutt (Eucalyptus pilularis), jarrah (Eucalyptus marginata), and messmate (Eucalyptus obliqua). These species provide a good test for the model based on their extreme diversity between wood properties and drying characteristics. The model uses boundary condition data from a series of vacuum-drying trials, which were also used to validate predictions. By using measured diffusion coefficient values to calibrate empirical formula, the accuracy of the model was greatly improved. Results of a sensitivity analysis showed that the model outputs provide excellent agreement with experimental observation despite the large range of species behaviour and variation in wood properties. This study confirms that the drying rate is significantly improved as a direct result of the enhanced convective and diffusive transfer along the board thickness. Contrary to softwood, it appears that longitudinal migration provides only a secondary effect. Not only is the model able to predict the heat and mass transfer behaviour of a range of hardwood species, it is also flexible enough to predict the behaviour for both conventional and vacuum-drying scenarios. The outcomes of this work provide the hardwood industry with a well-calibrated predictive drying tool that can be used to optimise drying schedules.

This paper presents an investigation on the structural potential of thin-walled timber structures compared to cold-formed steel and aluminium structures. The paper shows that manufacturing thin-walled timber profiles is possible. The manufacturing process is introduced herein. Specifically, short composite thin-walled timber Cee-sections (500 mm long) were fabricated by gluing together thin softwood (Araucaria cunninghamii) veneers (1 mm thick). Two types of Cee-sections were considered, one with an intermediate web stiffener to increase the local buckling capacity of the profile and one without. The profiles were tested in compression and the test results are presented and discussed in the paper in terms of structural behaviour and performance. A Finite Element model was also developed. Non-linear geometric analysis was carried out, with assumptions on observed delaminated areas, and the model was found to match the test results with reasonable accuracy. Further research directions are proposed in order to provide efficient and lightweight sustainable structural products to the construction industry.

International audience; AbstractKey messageHigh levels of percentage green veneer recovery can be obtained from temperate eucalypt plantations. Recovery traits are affected by site and log position in the stem. Of the post-felling log traits studied, out-of-roundness was the best predictor of green recovery.ContextEucalyptus globulus and Eucalyptus nitens are widely planted in temperate regions of the globe but few studies of rotary peeling have been documented.AimsThis study aims to examine differences among sites and log positions in post-felling log traits and green veneer recovery traits and determine the extent to which log traits explain variation in recovery traits.MethodsLog traits and green rotary-peeled veneer recovery traits from six temperate eucalypt plantations were studied. Selected plantations encompassed different age, site productivity, silvicultural and species classes in south-eastern Australia. Differences in log and recovery traits among sites and between lower and upper logs were examined, as was the extent to which log traits explained variation in recovery traits.ResultsDifferences among sites for percentage recovered green veneer were non-significant, despite significant differences for peelable billet volume, roundup loss, residual core diameter and all post-felling log traits: small end diameter, sweep, taper, out-of-roundness, end splitting and dynamic modulus of elasticity (MOEdyn). The lower log exhibited more sweep, taper and out-of-roundness but lower MOEdyn and less recovered green veneer. Out-of-roundness was the best predictor of recovery traits (R2 = 13–21 %, P

Australia’s utility pole network is aging and approaching its end of life. It is estimated that 70% of the 5 million poles currently in-service nationally were installed within the 20 years following the end of World War II and require replacement or remedial maintenance. Additionally, an estimated 21,700 high-durability new poles are required each year to support the expansion of the energy network. Utility poles were traditionally cut from native forest hardwood species. However, due to agreements which progressively phase out logging of native forests around Australia, finding new sources for utility poles presents a challenge. This paper presents the development of veneer based composite hardwood hollow utility poles manufactured from mid-rotation Gympie messmate (Eucalyptus cloeziana) plantation thinned trees (also referred to as “thinning”), as an alternative to solid hardwood poles. The incentives behind the project and benefits of the proposed products are introduced in the paper. Small diameter poles, of nominal 115 mm internal diameter and 15 mm wall-thickness, were manufactured in two half-poles butt jointed together, using 9 hardwood veneers per half-pole. The poles were tested in bending and shear, and experimental test results are presented. The mechanical performance of the hollow poles is discussed and compared to hardwood poles sourced from mature trees and of similar size. Additionally, the required dimensions of the proposed hollow pole to replace actual solid poles are estimated. Results show that the proposed product represents a viable technical solution to the current shortage of utility poles. Future research and different options for improving the current concept are proposed in order to provide a more reliable and cost effective product for structural and architectural applications in general.

Superior to hardwood and softwood trees, coconut palms are able to withstand extreme weather conditions without failure. Previous studies have shown that the internal structure of coconut palm stems significantly differs from hardwood, softwood and even other palm stems, in terms of fibre orientation and density distribution, likely influencing the mechanical characteristics of the tree. This paper aims at quantifying the cocowood hierarchical structure at an integral level (stem structure). To achieved this, quantitative analysis of more than 40 senile coconut palms from Fiji and Samoa has been carried out. This paper defines and analyses the typical cocowood morphology (form-structure) in terms of such factors as characteristic radius, fibrovascular bundles orientation and density distribution. For the first time, the characteristic triple helix configuration traced out by the fibrovascular bundles within the cocowood structure is modelled for the whole coconut stem. Specific equations are proposed to determine these factors at any given position in the tree. Knowledge advanced from this study will provide a scientific basis for future cocowood biomechanics research, including finite element modelling and analysis for biomimetic engineering applications.

Several key wood properties of four Australian hardwood species: Corymbia citriodora, Eucalyptus pilularis, Eucalyptus marginata and Eucalyptus obliqua, were characterized using state-of-the-art equipment at AgroParisTech, ENGREF, France. The wood properties were measured for input into microscopic (cellular level) and macroscopic (board level) vacuum-drying models currently under development. Morphological characterization was completed using a combination of environmental scanning electron microscopy and image analysis software. A clear difference in fibre porosity, size, wall thickness and orientation was evident between species. Viscoelastic properties were measured in the tangential and radial directions using dynamic mechanical analysis instrumentation. The glass transition temperature was markedly different for each species owing to anatomical and chemical variations. The radial direction showed higher stiffness, internal friction and glass transition temperature than the tangential direct...

International audience; AbstractKey messageLog-end splitting is one of the single most important defects in veneer logs. We show that log-end splitting in the temperate plantation speciesEucalyptus nitensvaries across sites and within-tree log position and increases with time in storage.ContextLog-end splitting is one of the single most important defects in veneer logs because it can substantially reduce the recovery of veneer sheets. Eucalyptus nitens can develop log-end splits, but factors affecting log-end splitting in this species are not well understood.AimsThe present study aims to describe the effect of log storage and steaming on the development of log-end splitting in logs from different plantations and log positions within the tree.MethodsThe study was conducted on upper and lower logs from each of 41 trees from three 20–22-year-old Tasmanian E. nitens plantations. Log-end splitting was assessed immediately after felling, after transport and storage in a log-yard, and just before peeling. A pre-peeling steam treatment was applied to half the logs.ResultsSite had a significant effect on splitting, and upper logs split more than lower logs with storage. Splitting increased with tree diameter breast height (DBH), but this relationship varied with site. The most rapidly growing site had more splitting even after accounting for DBH. No significant effect of steaming was detected.ConclusionLog-end splitting varied across sites and within-tree log position and increased with time in storage.

Two field trials were conducted with untreated coconut wood (“cocowood”) of varying densities against the subterranean termites Coptotermes acinaciformis (Froggatt) and Mastotermes darwiniensis Froggatt in northern Queensland, Australia. Both trials ran for 16 weeks during the summer months. Cocowood densities ranged from 256 kg/m3 to 1003 kg/m3, and the test specimens were equally divided between the two termite trial sites. Termite pressure was high at both sites where mean mass losses in the Scots pine sapwood feeder specimens were: 100% for C. acinaciformis and 74.7% for M. darwiniensis. Termite species and cocowood density effects were significant. Container and position effects were not significant. Mastotermes darwiniensis fed more on the cocowood than did C. acinaciformis despite consuming less of the Scots pine than did C. acinaciformis. Overall the susceptibility of cocowood to C. acinaciformis and M. darwiniensis decreases with increasing density, but all densities (apart from a few at the high end of the density range) could be considered susceptible, particularly to M. darwiniensis. Some deviations from this general trend are discussed as well as implications for the utilisation of cocowood as a building resource.

In Australia, plantation forests have increased in area by around 50% in the last 10 years. While this expansion has seen a modest 8% increase for softwoods, hardwood plantations have dramatically increased by over 150%. Hardwood plantations grown for high quality sawn timber are slow to mature, with a crop rotation time potentially reaching 35 years. With this long lead-time, each year the risk from fire, pests and adverse weather events dramatically increases, while not translating into substantially higher financial returns to the grower. To justify continued expansion of Australia’s current hardwood plantation estate, it is becoming necessary to develop higher value end-uses for both pulpwood and smaller ‘sawlog’ resources. The use of the low commercial value stems currently culled during thinning appears to be a necessary option to improve the industry profitability and win new markets. This paper provides background information on Australian forests and plantations and gives an overview of potential uses of Australian hardwood plantation thinning logs, as their mechanical properties. More specifically, this paper reports on the development of structural Veneer Based Composite (VBC) products from hardwood plantation thinning logs, taking advantage of a recent technology developed to optimise the processing of this resource. The process used to manufacture a range of hollow-form veneer laminated structural products is presented and the mechanical characteristics of these products are investigated in the companion paper. The market applications and future opportunities for the proposed products are also discussed, as potential benefits to the timber industry.

Australian utility pole network is aging and reaching its end of life, with 70% of the 5 million poles currently in-service nationally installed within the 20 years following the end of World War II. The estimated investment required for the replacement or remedial maintenance of the aging 3.5 millions poles is as high as 1.75 billion dollars. Additionally, an estimated 21,700 high-durability new poles are required each year, representing further investment of 13.5 million dollars per year. Yet, agreements which progressively phase out logging of native forests around Australia have been signed, giving the industry about 25 years to make the transition from Crown native forests to plantations and private forests. As utility poles were traditionally cut from native forest hardwood species, finding solutions to source new poles currently presents a challenge. This paper presents tests on Veneer Based Composite hardwood hollow utility poles manufactured from Gympie messmate (Eucalyptus cloeziana) plantation thinning. Small diameter poles of nominal 115 mm internal diameter and 15 mm wall-thickness were manufactured in two half-poles butt jointed together, using 9 veneers per halfpole. The poles were tested in bending and shear, and experimental test results are presented. The mechanical performance of the hollow poles is discussed and compared to hardwood poles cut from mature trees and of similar size. Future research and different options for improving the current concept are proposed in order to provide a more reliable and cost effective technical solution to the current shortage of utility poles.

The use of wood is seen as a sustainable alternative to reduce environmental impacts in building and construction sector. The low quality hardwood logs from plantation thinning are enhanced by producing engineered wood such as laminated veneer lumber (LVL). Nevertheless, engineered wood requires the use of chemicals and energy that may reduce its environmental benefits. A life cycle assessment (LCA) was conducted to compare the environmental performance of LVL produced from forestry thinning and final harvest to steel and concrete. The functional unit used in this study was a 1-m-long structural beam in a continuous beam system of 6-m-span designed according to the Australian standards. The Global Warming Potential (GWP) and embedded energy were assessed. The results indicated that LVL beam from thinned logs presented the lowest GWP impact (5.22kg-CO2-Eq). However, due to significant energy requirements for wood drying, the embedded energy in LVL was 186.78MJ which is only marginally less than steel (216.86MJ) but significantly less than concrete (352.82MJ). LVL from mature hardwood logs had slightly higher GWP than that produced from thinning; mainly due to extra energy and materials consumption in the plantation stage. Furthermore, LVL produced from mature trees had higher embedded energy than steel.

The colour of teak wood from plantations in Ghana was characterized by the International Commission on Illumination (CIE) L* a* b* colour measurement system in order to study the variations of wood colour parameters (lightness-darkness, redness-greenness and yellowness-blueness), among the different ecological zones. Teak trees totaling 46 were felled from 8 different plantation stands in four different ecological zones of Ghana (moist semi-deciduous forest, MSDF; dry semi-deciduous forest, DSDF; transition savanna forest; and savanna forest). Colour measurements were made on strips obtained from logs cut from the felled trees. Chemical analyses were performed on soil samples obtained from the rooting zones of the teak trees. Both environmental and tree age effects on colour were observed. However, environmental factors had a stronger effect on the colour of teak heartwood than the stand age. Although there were no significant differences between teak wood colour in moist semi-deciduous forest and transition savanna forest on one hand, and dry semi-deciduous forest and savanna forest on the other hand, in general, environment seemed to be an important factor, with teak wood colour being relatively darker in wetter areas than drier ones. Wood colour parameters showed differing relationships with soil chemical properties ranging from no relation through weak to moderate relations. For instance, soil pH decreased moderately with decreasing L* values (increasing darkness), indicating some evidence that teak wood colour may be predicted from soil pH. However, there was very little evidence that teak wood colour could be predicted from soil exchangeable cations (Ca 2+ , Mg 2+ , Na + and K + ). The range of observed site quality was rather limited. Nevertheless, richer plantation sites showed a tendency toward darker and less red heartwood.

International audience; The aim of this study was to propose an alternative non-deterministic and non-parametric technique for describing continuous variation in modulus of elasticity (E) within and between stems. The material studied consisted of hybrid Eucalyptus (Eucalyptus urophyllax X Eucalyptus grandis) stems felled at the age of 59 months. Samples for measuring E were taken along a diameter slab at 1.30 m above ground. The results showed that the proposed reconstruction technique is consistent compared to results from other studies on Eucalyptus. E increases from pith to bark, following a polynomial distribution. Local and tree-averaged E increased with cambial age, following a sigmoidal profile that can be described with five characteristic parameters (E at pith, E at inflection point, E after inflection point, cambial age when latency period ends, and cambial age at inflection point). The tree contributes little to the total variation. The most important changes in E value were found with increasing radial position, with this effect eight-fold more important than the tree effect.