Strengthening RC beams and columns with CFRP, GFRP and KFRP laminates

Prolonged exposure to adverse conditions affects the performance and promotes the degradation of reinforced concrete (RC) structures, requiring repair and strengthening to preserve their integrity and functionality. Synthetic fibers, including carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP), are frequently employed for retrofitting owing to their superior strength-to-weight ratio and simple installation. Natural fibers, such as kenaf, have been increasingly incorporated into fiber reinforced polymer (FRP) composites as sustainable alternatives in the construction industry due to their lightweight nature and low carbon footprint. Yet, many investigations focused on synthetic fibers, thus, the purpose of this study is to develop finite element (FE) models for RC beams and columns retrofitted with CFRP, GFRP and kenaf fiber reinforced polymer (KFRP), to examine the impact of natural fibers and comparing the findings with those derived from synthetic fibers. The models consider element types, mesh discretization, solution methodologies, and nonlinearities. Concrete behavior is represented using Concrete Damage Plasticity (CDP), whereas fiber laminates employ the Hashin damage model. The FE model's load-displacement behavior, ultimate strength, and failure mechanisms were verified against existing experimental and numerical findings. The findings indicate that FRP wrapping substantially enhances the load-carrying capacity of RC beams, with ultimate load increases ranging from approximately 13% for KFRP to 66% for CFRP, whereas the corresponding improvements for RC columns are notably smaller, remaining below 7%. Although KFRP exhibits lower mechanical performance than GFRP and CFRP, its sustainability and cost-effectiveness support its use in applications where environmental and economic considerations are prioritized.