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 $1680\text{ mm}$ by $150\text{ mm}$ $120\text{ mm}$ 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 $681.4:655.4\text{ kg/m}^3$, Pterygota macrocarpa is $648.00\text{ kg/m}^3:479.60\text{ kg/m}^3$ and Antiaris toxicaria is $471.79\text{ kg/m}^3:445.75\text{ kg/m}^3$ of solid to glulam respectively, while maximum load on each specie from flexural strength test indicated that, Guarea cedrata is $29.90\text{ kN}:15.6\text{ kN}$, Pterygota macrocarpa was $29.7\text{ kN}:14.43\text{ kN}$ and, Antiaris toxicaria is $14.13\text{ kN}:9.6\text{ kN}$ 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 $23.60\text{ N/mm}^2; 23.83\text{ N/mm}^2$, Pterygota macrocarpa $17.68\text{ N/mm}^2; 15.83\text{ N/mm}^2$ and Antiaris toxicaria $13.84\text{ N/mm}^2; 17.11\text{ N/mm}^2$ meanwhile compressive strength when loaded perpendicular to the grain the mean result for the solid and glulam of each species are $8.67\text{ N/mm}^2; 8.71\text{ N/mm}^2$ for Guarea cedrata, $5.22\text{ N/mm}^2; 7.69\text{ N/mm}^2$ for Pterygota macrocarpa and $7.21\text{ N/mm}^2; 6.63\text{ N/mm}^2$ 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