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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.

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.