Experimental investigation of material and joint influence on timber I-beam performance

Abstract

This study experimentally investigates the influence of web material and joint configuration on the flexural performance of timber I-beam configurations. A total of 27 specimens representing nine beam types were tested, including oriented strand board (OSB), laminated timber, and plywood-web beams produced as continuous, web-joined, and flange-joined members. Three-point bending tests were conducted over a clear support span of 1000 mm, and the load–displacement response, maximum load capacity, stiffness, energy absorption, strength-to-weight ratio, and failure modes were evaluated. The results showed that continuous specimens generally achieved higher load-bearing capacities than their joined counterparts, indicating the importance of uninterrupted load transfer. Among the tested configurations, the continuous plywood-web beam exhibited the highest mean maximum load of 28.569 kN and the highest strength-to-weight ratio of 6.93 kN/kg. OSB-web beams showed lower absolute load capacity but a competitive strength-to-weight ratio of 5.45 kN/kg, suggesting potential for lightweight applications. Web-joined specimens generally performed better than flange-joined specimens because flange continuity provided more effective resistance to bending-induced tensile and compressive stresses. Failure observations indicated that joint location influenced damage initiation, web–flange separation, adhesive debonding, and post-peak behavior. Since the specimens represented practical beam configurations incorporating locally available, unused, or previously used wood-based components, the findings should be interpreted at the configuration level rather than as isolated material-property comparisons. Overall, the study provides practical insight into material selection and joint detailing for sustainable timber I-beam applications.