Flexural Performance of Glued Laminated Timber Beams Reinforced by the Cross-Section Increasing Method

This article addresses the problem of insufficient bearing capacity and stiffness in laminated timber beams during use and proposes a reinforcement method by increasing the cross-section. Twenty glued laminated timber beams with dimensions of 2850 mm × 120 mm × 50 mm were produced using Pinus sylvestris var. mongolica as the raw material. Douglas fir with good tensile properties and new self-tapping screws were selected as reinforcement materials. Through adhesive bonding and adhesive–nail combination methods, an enlarged section reinforcement beam was formed. The influence of section height, bonding process, and the arrangement of self-tapping screws on the bending performance of three groups of six adhesive-reinforced specimens and three groups of fourteen adhesive–nail reinforced specimens was examined through bending performance tests. The results showed that compared with specimens reinforced with single-layer panels, the ultimate load of specimens reinforced with double-layer panels increased by 22.82 to 29.49%, and bending stiffness increased by 17.26 to 48.17%. Within the same group, the ultimate load of specimens reinforced with standard compressive stress adhesive increased by 3.88 to 5.71% under bending. Compared with adhesive reinforcement specimens, adhesive–nail combined reinforcement specimens showed an 8.91 to 11.36% increase in ultimate load. In specimens with the same screw insertion angle, the ultimate bearing capacity of beams reinforced with longer screws and smaller spacing was actually lower. Moreover, the ultimate load of specimens reinforced with self-tapping screws inserted at 90° was 4.2% higher than that of specimens with screws inserted at 45°.