Blue gum: assessment of its potential for glued laminated timber beams

Abstract

Portuguese forests are mainly composed of hardwoods, which represent 69% of the forest area in 2010, being Blue gum (Eucalyptus globulus Labill.) the most abundant species (26%). The suitability of Blue gum for structural applications was demonstrated in previous studies. However, the most common uses are still related to the pulp and paper industry as well as energy production, mainly due to sawing and drying issues. The present paper describes a preliminary study on the potential application of non-destructive tests and analytical methods to predict the most important mechanical properties of glued laminated timber (glulam) beams made of Blue gum. The potential of mixed beams made of Blue gum and poplar was also analysed. The longitudinal vibration method and the transformed section method were considered. A total of 11 non-finger jointed full-scale glulam beams (7 of Blue gum and 4 mixed) were manufactured in the laboratory and tested for modulus of elasticity and bending strength assessment. After the bending tests, the density and moisture content of the beams were determined, and the bonding performance was checked by delamination and shear strength tests. Correlation coefficients were established between the predicted values and the experimentally assessed mechanical properties, indicating a huge potential of the predictive methods used. The mechanical properties of non-finger jointed beams tested were above the typical values found in the literature for the most common hardwoods available in European forest.