Reinforcement of variable-height glulam beams under perpendicular-to-grain stress
Abstract
This study presents a comprehensive numerical investigation of reinforcement strategies for glued laminated timber beams under perpendicular-to-grain tensile stresses, focusing on three critical geometries: double-tapered (DT, initial work rate Wᵣ=0.82), pitched cambered (CV, Wᵣ=2.54), and curved with constant inertia (CC, Wᵣ=1.71). Using RX-TIMBER finite element analysis compliant with Eurocode 5, the research evaluates three reinforcement systems, glued-in steel rods, glued solid wood strips, and wood-based plates, identifying optimal configurations that reduce stress utilization ratios below unity. For pitched cambered beams, 24 steel rods (20 mm diameter) or 12 C30 wood strips (2 cm thickness) achieve 70% work rate reduction, while constant-inertia curved beams require 16 steel rods (16 mm) or 10 C30 wood strips, with 0.8 cm F25/10 plates in parallel arrangement reducing work rates to 0.41 (76% reduction). Ultra-thin 0.2 cm F60/10 plates demonstrate equivalent performance for high-strength applications. Critical design parameters include 3/4 external-to-internal element ratios, maximum 0.8 m spacing between elements, and thickness thresholds of 0.4-0.8 cm for plates and 16–20 mm for rods. Wood-based solutions match metal reinforcement performance when using equivalent strength classes, offering 30% cost reductions and 40% faster installation. The study provides validated design guidelines for sustainable timber structures in seismic or high-moisture environments, addressing critical gaps in comparative performance data for curved beam reinforcement while enabling optimized material use and maintained structural integrity.
Reference
Gaël FEKO NGNONGUINI; René Thierry DJOUMESSI; François Beceau PELAP. (2026). Reinforcement of variable-height glulam beams under perpendicular-to-grain stress. Elsevier BV. https://doi.org/10.2139/ssrn.6298552
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