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Developing higher-value structural products from fast-growing eucalypt plantations - that are currently managed for woodchip production - can create new markets for these plantation resources and ensure a sustainable supply of timber for building construction. In this study, structural nail-laminated timber (NLT) panels with different span lengths were manufactured from a 16-year-old fast-grown Eucalyptus nitens plantation using a lamination system that can maximise the use of lower-grade boards in NLT production. The short-term bending performance in the elastic region and the effects of environmental conditions and structural grade of timber on long-term bending creep deflection of the panels were evaluated. The data analysis revealed that the current visual stress-grading method is incapable of estimating the actual modulus of elasticity (MOE) of the plantation Eucalyptus nitens timber. A linear regression model was proposed using the actual MOE of the boards that can predict the MOE of NLT panels with an average accuracy of 98%. The NLT panels made with higher-grade boards showed 22.4% greater MOE values than the NLT panels made with lower-grade boards. The lamination system used resulted in NLT panels with predictable and customised MOE with a remarkable average coefficient of variance of less than 2.6%. The long-term bending creep deflection of the test panels was significantly affected by daily variations in the relative humidity of the environment and structural grade of the timber used. The results of this study can be used in the development of an appropriate NLT production system from fast-grown plantation eucalypt.

Australia’s hardwood plantation estate is predominantly comprised of Eucalyptus nitens and Eucalyptus globulus, which are mainly being managed to produce woodchips—a low-value commodity export. There is an increasing interest by the timber industry in developing higher-value structural products from the low-grade timber recovered from these plantation resources. In this experimental study, for the first time, the bending performance of nail-laminated timber (NLT) and NLT-concrete composite (NLTC) floor panels constructed of the low-grade, fibre-managed Eucalyptus nitens and Eucalyptus globulus timber was evaluated. The test panels were constructed with various span lengths and cross-sectional configurations and subjected to vibration and four-point bending tests. The results indicated that the modulus of elasticity of the Eucalyptus nitens NLT panels (11,074.6 MPa) was comparable to that of NLT panels made of Eucalyptus globulus (11,203.2 MPa). The modulus of rupture of the Eucalyptus globulus panels was 13.8% higher than that of the Eucalyptus nitens ones. The bending properties of the NLT panels constructed of the two plantation species were superior to those of some commercially important mass laminated timber products reported in the literature. Under the limit state design loads, all the NLT and NLTC panels were still in the linear-elastic range. The fundamental natural vibration frequency values of the test panels were above the recommended minimum range of 8–10 Hz for residential and office floors. The two plantation timber species therefore demonstrated sufficient short-term bending performances to be used in the construction of higher-value structural floor products.

This study evaluated the termite susceptibility of Papua New Guinea (PNG) balsa (Ochroma pyramidale) against Australia's most economically important wood-destroying termite species, Coptotermes acinaciformis. Samples of envelope treated PNG balsa with the insecticide bifenthrin and non-treated balsa, radiata pine (Pinus radiata) sapwood and southern blue gum (Eucalyptus globulus) heartwood were exposed to seven different colonies of C. acinaciformis at a field site in the Northern Territory, Australia. The results indicated that balsa is susceptible to termite attack, with a mean mass loss of 30.9% (range 3.8–99.9%). Mean mass losses for radiata pine and southern blue gum were 90.3 and 98.9% respectively. It was evident that balsa can be successfully protected from termite attack with envelope-treatments of bifenthrin, with the latter proving to be highly efficacious at mass/volume retentions much lower than those specified in AS 1604.1 and typically used in the Australian timber preservation industry.

The main goal of this study was to investigate the visual characteristics, recovery rate, and flexural properties of sawn boards from a fibre-managed plantation Eucalyptus globulus resource as a potential raw material for structural building applications. The impacts of the visual characteristics, strength-reducing features, and variation in basic density and moisture content on the bending modulus of elasticity (MOE) and modulus of rupture (MOR) of the boards were investigated. The reliabilities of different non-destructive methods in predicting MOE and MOR of the boards were evaluated, including log acoustic wave velocity measurement and numerical modellings. The MOE and MOR of the boards were significantly affected by the slope of grain, percentage of clear wood, and total number of knots in the loading zone of the boards. The normal variation in basic density significantly influenced the MOE of the boards while its effect on the MOR was insignificant. The numerical models developed using the artificial neural network (ANN) showed better accuracies in predicting the MOE and MOR of the boards than traditional multi-regression modelling and log acoustic wave velocity measurement. The ANN models developed in this study showed more than 78.5% and 79.9% success in predicting the adjusted MOE and MOR of the boards, respectively.

The aim of this study was to examine the impacts of visual characteristics, strength-reducing features (SRFs), and basic density on the mechanical properties of fibre-managed plantation Eucalypt timber to create effective structural grade groups. It is the intension that the results found in this study can lead to the development of a visual stress grading method for fibre-managed plantation timber in the future and influence the development of new applications for the resource in structural elements for the built environment. The plantation specie investigated in this study was Eucalyptus Nitens–390 sawn timber boards. The most important visual characteristics and SRFs likely to influence the mechanical properties of the boards were visually identified and measured before the boards were divided into designated groups for sampling. The impacts of the visual characteristics, SRFs, and basic density of the boards within each group on modulus of elasticity (MOE) and modulus of rupture (MOR) were determined using four-point bending test. The statistical analyses suggest three structural grade groups can categorise the resource. Strong correlations were found between MOE, MOR, and basic density with the visual characteristics and SRFs of the boards in the three grade groups.

This study tested the machinability of three major timber species grown in Tasmania, Australia, under different resource management schemes: plantation fiber-managed hardwood (Eucalyptus globulus Labill. and Eucalyptus nitens Maiden) and plantation sawlog-managed softwood (Pinus radiata D. Don). P. radiata was used as a control to identify significant differences in machining fibre-managed plantation timber against sawlog-managed plantation timber with numerically controlled computer technology and manually fed timber production techniques. The potential to fabricate architectural interior products such as moldings with plantation fiber-managed hardwood timber that is high in natural features was the focus of this study. Correlations between wood species, variation in moisture content, and density of individual machinability characteristics were analyzed to determine factors impacting the overall quality of plantation wood machinability. Correlations between species and within species groups from the resulting machinability tests are highlighted and discussed. The results indicate that the machinability of sawlog-managed softwood P. radiata is superior in some circumstances to fiber-managed hardwood E. globulus and E. nitens specimens, according to the American Society for Testing and Materials D1666-11.

The use of fast-growing plantation eucalypt (i.e., pulpwood eucalypt) in the construction of high-value structural products has received special attention from the timber industry in Australia and worldwide. There is still, however, a significant lack of knowledge regarding the physical and mechanical properties of the lumber from such plantation resources as they are mainly being managed to produce woodchips. In this study, the physical and mechanical properties of lumber from a 16-year-old pulpwood Eucalyptus nitens H.Deane &amp, Maiden resource from the northeast of Tasmania, Australia was evaluated. The tests were conducted on 318 small wood samples obtained from different logs harvested from the study site. The tested mechanical properties included bending modulus of elasticity (10,377.7 MPa) and modulus of rupture (53 MPa), shear strength parallel (5.5 MPa) and perpendicular to the grain (8.5 MPa), compressive strength parallel (42.8 MPa) and perpendicular to the grain (4.1 MPa), tensile strength perpendicular to the grain (3.4 MPa), impact bending (23.6 J/cm2), cleavage (1.6 kN) and Janka hardness (23.2 MPa). Simple linear regression models were developed using density and moisture content to predict the mechanical properties. The variations in the moisture content after conventional kiln drying within randomly selected samples in each test treatment were not high enough to significantly influence the mechanical properties. A relatively high variation in the density values was observed that showed significant correlations with the changes in the mechanical properties. The presence of knots increased the shear strength both parallel and perpendicular to the grain and significantly decreased the tensile strength of the lumber. The results of this study created a profile of material properties for the pulpwood E. nitens lumber that can be used for numerical modelling of any potential structural product from such a plantation resource.

We determined the effects of adhesive type and loose tenon dimensions (length and thickness) on bending strength of T-shaped mortise and loose-tenon joints. Polyvinyl acetate (PVAc) and two-component polyurethane (PU) adhesives were used to construct joint specimens. The bending moment capacity of joints increased significantly with increased length and thickness of the loose tenon. Bending moment capacity of joints constructed with PU adhesive was approximately 13% higher than for joints constructed with PVAc adhesive. We developed a predictive equation as a function of adhesive type and loose tenon dimensions to estimate the strength of the joints constructed of oriental beech (Fagus orientalis L.) under uniaxial bending load.

This investigation was conducted to determine the feasibility of using a two-component polyurethane (PUR) adhesive, with special waterproof properties, in constructing wooden structures. We designed and conducted tests to compare the shear strength and adhesion performance of PUR with polyvinyl acetate (PVAc) adhesive on block-shear specimens constructed of oriental beech (Fagus orientalis L.), fir (Abies alba Mill.), poplar (Populus deltoides Bartr.), white oak (Quercus alba L.), sycamore (Platanus orientalis L.) and white walnut (Juglans cinerea L.). The values of the percentage of wood failure were also determined in specimens constructed with each adhesive. The highest shear strength values of both adhesives were obtained in specimens constructed of beech, while the lowest shear strength values were obtained in fir and poplar specimens. Average shear strength of the PUR adhesive was 16.5% higher than that of the PVAc adhesive. Specimens constructed of fir, poplar and sycamore were characterised by the highest percentages of wood failure, whereas the lowest average percentages of wood failure were obtained in beech and oak specimens. With the exception of oak specimens, there was no statistically significant difference between percentage of wood failure among the PUR and PVAc adhesives. Generally, the PUR adhesive showed an acceptable adhesion performance on wood materials used in our study.

The main goal of this study was to determine the effect of wood species and loose tenon length on the withdrawal force capacity of mortise and loose tenon (M&LT) T-type furniture joints. The specimens were manufactured from oak (Quercus alba), beech (Fagus orientalis L.), poplar (Populus deltoides), sycamore (Platanus orientalis), fir (Abies alba), and white walnut (Juglans cinerea), and the tenon species selected was oriental beech (Fagus orientalis L.). The length of the tenon was determined on the basis of the length glued into the horizontal member of the joint. The lengths in the present study were 10, 20, and 30 mm. It was found that joints manufactured from beech had the highest withdrawal force capacity; this trait was lowest in joints made from the light wood of poplar and fir. The glued-in length of the tenon exerted a significant influence on the withdrawal force capacity of the joints. The greatest withdrawal force capacity increment of M&LT T-type joints was obtained when the tenon length changed from 10 to 20 mm.