Effect of different reinforcement methods on the flexural performance of glued laminated timber beams

Glued laminated timber beams are vulnerable to brittle tensile failure in the tension zone, which limits their flexural efficiency and application in modern timber structures. This study investigated two reinforcement strategies for such beams: external steel reinforcement and bottom steel plate reinforcement connected with self-tapping screws. Unreinforced beams were tested as controls. Full-scale four-point bending tests were conducted to evaluate failure mode, load-deflection response, load-strain behaviour, bearing capacity, stiffness, and ductility. A three-dimensional finite element model was then developed and validated against the experimental results. The control beams failed in brittle tension, with an average ultimate load of 21.6 kN. The externally reinforced beams showed no effective improvement in flexural behaviour because prestress transfer and steel-timber interaction were insufficient. In contrast, the steel plate reinforcement restored 76% of the original load-bearing capacity of damaged beams and improved deformation capacity, although failure was still governed by timber delamination and screw shear. The validated numerical model reproduced the full loading-to-failure process and can support the design and optimization of reinforced timber members.