Comparison and Investigation of the Behavior of Reinforced Wooden Beams with Notches at the Ends

When manufacturing wooden beams for spanning, notches are often formed at the ends. Under load, stresses develop at these notches, often causing cracks and beam failure. This study theoretically and experimentally investigated methods to reinforce such beams. Two types of calibrated beams were tested: solid timber and glued laminated beams. In experimental tests, beams were fixed in a machine to simulate mid-span “three-point” bending. Parallel theoretical evaluations followed EN 1995-1-1: Eurocode 5 and STR 2.05.07:2005 design standards. For each beam type, three groups of specimens were prepared: unreinforced, end-reinforced with dowels, and end-reinforced with plywood strips. All beams failed similarly: cracks formed at the notches and grew until the beam lost the load-bearing capacity. Failure behavior differed from typical bending tests, but the mechanical properties of unreinforced beams depended on cross-section. Dowel reinforcement effectiveness theoretically increased with the number of dowels, though excessive dowels risked splitting the wood. In tested beams, dowels nearly doubled the load capacity (6.5–24.0 kN on average). Plywood strip reinforcement improved resistance by up to 10 kN, equivalent from several percent to 2.5 times the original capacity. Beams with end notches, used in spans, can be evaluated under load using EN 1995-1-1: Eurocode 5 and STR 2.05.07:2005 methods. The study showed that differences between theoretical calculations and experimental results on calibrated structural timber did not exceed 17 %.