Study On Mechanical Behavior Of Glued Laminated Timber

As one of the most widely used materials in modern timber structures, glulam has drawn high attention all over the field. However, research on mechanical properties of glulam mainly focuses more on the uniaxial stress state rather multiaxial stress state. In our work, the mechanical experiments were conducted on the glulam of the same lamina grade subjected to uniaxial and biaxial loading. Their corresponding failure modes, failure strength and stress-strain curve are obtained. Accordingly, the applicability of some typical wood strength criteria are discussed. This study provides reference for design calculations and numerical simulations for wood structures.The major contributions of work are summarized as follows:1. The failure strength and the failure modes of glulam under uniaxial stress are compared, between two cases one takes the friction-reduction measures, and the other doesn’t. The influence of the lateral friction constraints on the glulam cube specimen is discussed.2. Tests on uniaxial compression and tension of the glulam at three material axes are carried out respectively. The results show that the difference of the mechanical properties for glulam between tangential and radial to the grain is negligible, however, the discrepancy of the mechanical properties for glulam between parallel and perpendicular to the grain is too tremendous to be ignored. Moreover, the failure modes of the glulam under uniaxial tension is typically brittle fracture; and the behavior of the glulam under uniaxial compression is dominated by the plastic deformation.3. Referred to the biaxial test methods of the concrete, the failure strength and the failure modes of glulam under biaxial compression, biaxial compression-tension and biaxial compression-shear stress were measured respectively. Accordingly, the applicability and accuracy of the wood failure criteria in the glulam are discussed. According to the results, the optimal strength criteria for different stress state are obtained.4. The influence of the compression radial to grain on the strength of glulam under biaxial compression-shear is not negligible. And the influence of the compression parallel to grain on the strength of glulam under biaxial compression-shear cannot be described accurately by the wood strength criteria in the literatures.