Flexural Properties of Structural Size Glulam Beams Made from Indonesian Wood Species: Experimental Programs

This study was conducted as part of an effort aimed to establish glulam standard prepared from Indonesian wood species. At first, bending strength and stress-strain curve in both tension and compression parallel-to-grain tests of clear specimens were performed for nine potential wood species, including Jabon, Pine, Mahogany, Acacia, Rubber wood, Merbau, Keruing, Meranti Batu, and Bangkirai. Subsequently, another test was carried out on glulam beams of Jabon and Keruing species, prepared by two local producers for different sizes (Beam A: cross-section of 140 mm by 200 mm, length of 3,700 mm; Beam B: cross-section of 140 mm by 250 mm, length of 4,600 mm). Polyurethane and phenol resorcinol formaldehyde adhesives were used in glulam production of Jabon and Keruing beams, respectively. The beams were tested until failure under the four-point loading configuration described in EN 408:2012 to examine flexural properties, modulus of rupture, modulus of elasticity, and failure modes. The results of the clear specimen test showed that the bending strength, tensile strength, and compressive parallel-to-grain strength increased with higher wood density. A linear stress-strain model in the tension zone and a bi-linear stress-strain relationship in the compression zone were necessary to properly simulate the structural properties of glulam beams. Considering the modulus of rupture, the tested glulam beams of Jabon and Keruing could be classified as GL30h and GL56h, respectively. Based on a visual examination of beam failure after completing the bending tests, some recommendations for glulam production improvement were proposed.