Effect of lamination anisotropy and lay-up in glued-laminated timbers

This paper presents the analysis of glued-laminated timbers (glulam) subjected to tension perpendicular to the fiber direction, hereby taking into account the cylindrical anisotropy of the individual laminations and specific lay-up configurations. The investigations include two- and three-dimensional finite element analyses of prismatic specimens and curved beams. The influences of the board width and the location of the board's material coordinate system, i.e., of the sawing pattern, were studied parametrically. The stress distributions obtained deviate considerably from results based on simplified orthotropic constitutive theory, which is commonly applied in the analysis of glulam. The study showed a strong influence of the lamination sawing pattern and of the grouping within the glulam cross section. The maximum stress values exceeded the stresses obtained assuming rhombic orthotropy by a factor of about 2-4. The strength relevant Weibull stresses, which smooth the true uneven stress distributions, revealed increases of about 1.4-1.9. This work provides enhanced understanding of glued-laminated timbers in transverse tension loading and can be used as a theoretical tool for optimization of lay-ups.