Eastern Hemlock in Bamboo-Reinforced Glulam

Abstract

Eastern hemlock (Tsuga canadensis) is an abundant yet underutilized low-value tree species native to the northeast region of the United States. Developing value-added markets for these trees would improve local forest management and bolster local forest economies. This paper presents an analytical and experimental investigation into the structural capabilities of double vertical glue-laminated eastern hemlock beams that are reinforced with a tensile layer of laminated veneer bamboo (LVB). LVB is a sustainable engineered bamboo product with appreciable and reliable tensile strength. This study examines the effect of LVB reinforcement on failure modes, bending strength, stiffness, ductility, and design values of eastern hemlock beams. Analytical methods are presented for modeling nonlinear structural behavior of beams in bending and inspecting failure modes for different wood strengths, followed by finite-element modeling of both reinforced and unreinforced beams. Four-point bending tests were conducted and the results confirmed the analytical predictions. Tests indicated a 16% increase in beam stiffness and an 81% increase in characteristic (fifth percentile) modulus of rupture (MOR). A methodology is proposed for determining optimum rate of reinforcement for structural performance.