Glued-Laminated Beams: Assessment Of Physio-Mechanical Properties Of Locally Selected Timber Species

Timber application has a long history as a building material due primarily to his continued use for framing, cladding, flooring and flooring for major construction such as bridges, wharves, railways, sleepers etc. as well as domestic and industrial buildings. This paper assesses the suitability of three selected Nigerian timber species namely; Guarea cedrata, Pterygota macrocarpa and Antiaris toxicaria in production of Glued-laminated (glulam) beams. The glulam beams were produced with the use of polyvinyl acetate glue (PVA). Physical properties of the timber species such as moisture content (MC) and densities were determined using BS EN 304:2001. The beams produced which are 1680 mm by 150 mm 120 mm in dimension were later subjected to four point loading system to determine their flexural strengths and failure loads in accordance with ASTM D-198,(2003). The results produced showed that, the density of Guarea cedrata is 681.4:655.4 kg/m³, Pterygota macrocarpa is 648.00 kg/m³:479.60 kg/m³ and Antiaris toxicaria is 471.79 kg/m³:445.75 kg/m³ of solid to glulam respectively, while maximum load on each specie from flexural strength test indicated that, Guarea cedrata is 29.90 kN:15.6 kN, Pterygota macrocarpa was 29.7 kN:14.43 kN and, Antiaris toxicaria is 14.13 kN:9.6 kN for solid and glulam beams respectively. Compressive strength results showed that when loaded parallel to grain the mean result of the timber species are Guarea cedrata 23.60 N/mm²; 23.83 N/mm², Pterygota macrocarpa 17.68 N/mm²; 15.83 N/mm² and Antiaris toxicaria 13.84 N/mm²; 17.11 N/mm² meanwhile compressive strength when loaded perpendicular to the grain the mean result for the solid and glulam of each species are 8.67 N/mm²; 8.71 N/mm² for Guarea cedrata, 5.22 N/mm²; 7.69 N/mm² for Pterygota macrocarpa and 7.21 N/mm²; 6.63 N/mm² for Antiaris toxicaria. Solid beams have more flexural strength than the glulam beams and Glulam beams have high compressive strength than solid beams when loaded parallel and perpendicular to grain