Flexural behavior and load-bearing capacity calculation methodology for wooden beams strengthened using aluminum plates attached with self-tapping screws

To investigate the flexural failure mode and behavior of wooden beams strengthened using aluminum (Al) plates, which were attached with self-tapping screws and structural adhesive, ten specimens were tested in bending. The experimental parameters were the thickness of the bottom Al plate, the longitudinal and transverse grain spacing of the self-tapping screws. The experimental results revealed that (1) compared with unreinforced beams, the reinforced beams exhibited ultimate load capacity and displacement ductility coefficients that were 18.4%-54.3% and 6.4%-43.1% higher, respectively; (2) for the same Al plate thickness in the tensioned area, the initial stiffness of the reinforced wooden beams increases as the longitudinal grain spacing of the screw grains decreases; (3) the plane-section assumption was satisfied by the strain in the middle section of the Al plate-reinforced wooden beam along the height; (4) the strains at the same position in the wooden beam and Al plate were similar, thus indicating that the wooden beam and Al plate behaved collectively. Furthermore, a formula was proposed for calculating the flexural capacity of an Al plate-reinforced wooden beam, thus providing a valuable reference when designing wooden beam reinforcements.