Structural Interaction Between Woven Kenaf FRP Plates and Notched Concrete Beams Under Flexural Loading

Concrete is widely recognised for its durability and high compressive strength, making it one of the most utilised construction materials globally. However, structural elements such as beams are often subjected to defects, including notches and cracks, which reduce their load-carrying capacity and necessitate effective strengthening solutions. Fibre Reinforced Polymer (FRP) systems have been extensively applied to enhance structural performance. Kenaf FRP (KFRP) is a promising natural alternative due to its high tensile strength and sustainability. This study examines the flexural performance of notched concrete beams reinforced with woven KFRP plates, aiming to enhance load-carrying capacity through experimental testing and validation via three-dimensional finite element analysis. The research involves three standardised notched-depth beam designs, with 18 specimens tested under four-point bending. Failure modes and ultimate load capacities were analysed, revealing dominant mechanisms such as flexural cracking and KFRP rupture. The results indicate that KFRP strengthening increased the ultimate load capacity by up to 200% compared to unstrengthened beams. Additionally, the Extended Finite Element Method (XFEM) with traction-separation laws was employed to predict flexural strength, demonstrating a strong correlation with experimental results, with mean variances below 6%. The numerical approach is a reliable predictive tool for estimating the flexural strength of notched beams reinforced with natural FRPs. Experimental and numerical findings confirm that KFRP plates significantly improve the flexural strength of notched concrete beams, highlighting their potential as an effective and sustainable retrofitting solution for deteriorated concrete structures.