Sousa H.S., Branco J.M., Lourenço P.B. (2013). Glulam Mechanical Characterization. Trans Tech Publications: Materials Science Forum, Advanced Materials Forum VI, Vols. 730-732. pp 994-999. (doi.org/10.4028/www.scientific.net/MSF.730-732.994) Glulam Mechanical Characterization Hélder S. Sousa 1, a , Jorge M. Branco 1,b and Paulo B. Lourenço 1,c 1 Universidade do Minho – Dept. of Civil Engineering, Azurém, 4800-058 Guimarães, Portugal a hssousa@civil.uminho.pt, b jbranco@civil.uminho.pt, c pbl@civil.uminho.pt Keywords: glued laminated timber; strength class; bending; tension parallel to the grain. Abstract. The glued laminated timber (glulam) mechanical properties may be evaluated through the determination of the key mechanical properties of the lamellae that compose that element. Simple bending and tension parallel to the grain tests were performed in order to assess the strength class of three glulam elements. Regarding the bending tests, 8 samples were taken from a glulam beam and assessed. Values for the resistant bending tension and both local and global modulus of elasticity were obtained. For the tension parallel to the grain tests, a total of 120 samples were assessed. The samples were divided regarding the structural element from where they were extracted as well to the type of failure mode found in the tests. The values of the lamellae properties were then used for determination of the properties of the glulam material. The data gathered from the tests was assessed statistically and concluded that the mechanical properties of the glulam elements did not fulfill the required parameters of the normative requirements. Introduction Each material used in a construction site should be subjected to a thorough evaluation of its mechanical properties, in order to avoid possible structural hazards. This evaluation comprises not only the characterization of the material properties and its conformity to the allegedly resistant class, but also the inspection to its physical properties. For this purpose, mechanical tests combined to visual inspections are often used to grade the material in terms of strength class. Timber is a rather complex material due to its anisotropic behavior and therefore, when used in a construction site, its mechanical properties must be assessed with a higher degree of confidence than for other materials such as alloys or concrete. Many derivative wood products (e.g. glued laminated timber (glulam), plywood, oriented strand boards (OSB) and others) have more uniform mechanical properties, mainly due to the intent of minimizing the influence of defects in timber (e.g. nodes, cracks, misalignment of fibbers) with the production process. This is often achieved by using different layers or fragments of timber glued or compressed in different directions, creating a new material. The glulam manufacturing process consists in the gluing of overlaid lamellae of timber. This overlaying is made in such manner that the orientation of the fibbers in each lamella is parallel to the remaining ones. In order to obtain larger spans, finger-joints or other equivalent connections are used to bond different timber elements in the same horizontal layer. This manufacturing process permits a selection of timber elements with a reduction of the presence and influence of defects. The tendency for cracking is reduced, since the stresses generated on a lamella are resisted and absorbed by the neighboring lamellae. The standard NP EN 1194:1999 [1] has indicative values for definition of the strength class of glulam elements (Table 1) and also proposes correlation functions to obtain the properties of a glulam element from the properties of the composing lamellae. The work presented in this paper concerns the mechanical characterization of different glulam elements using simple bending tests and tension parallel to the grain tests. The material in study was classified as a GL28h by the manufacturer. The mechanical properties of glulam elements are