Influence of NSM reinforcement with steel bars and different adhesives on the bending behavior of paricá LVL beams

Although Near Surface Mounted (NSM) reinforcement has been widely investigated for timber structures, there is still a scarcity of scientific studies addressing the strengthening of paricá laminated veneer lumber (LVL). Therefore, this study evaluated the influence of NSM reinforcement on the apparent density, maximum bending moment, and stiffness of paricá LVL through experimental tests conducted on unreinforced beams and on beams reinforced in the central region with one steel bar (compression zone) or two steel bars (compression and tension zones), bonded with epoxy (EPX) and castor-oil-based polyurethane (PUR) adhesives. The experimental results for maximum bending moment were compared with numerical simulations based on the finite element method and with analytical predictions obtained using the transformed-section method. The results demonstrated that NSM reinforcement increased apparent density and improved the bending performance of all reinforced configurations, with the most significant gains observed for beams reinforced with two steel bars bonded with epoxy adhesive, which achieved a 28.45% increase in maximum bending moment compared with the Control series. The use of two reinforcement bars was more effective than a single-bar configuration. The PUR adhesive showed lower mechanical performance and greater variability, particularly in the PUR-1R series, which exhibited no significant improvement in bending capacity. In contrast, EPX-bonded specimens exhibited superior mechanical performance and more uniform behavior. Numerical simulations adequately reproduced the experimental behavior and highlighted the stress redistribution promoted by the reinforcement, while the analytical method overestimated the maximum bending moment. Overall, the results confirm the potential of NSM reinforcement for paricá LVL beams and highlight the significant influence of reinforcement configuration and adhesive type.