<p>Retrofitting reinforced concrete beams with externally bonded steel plates (EBSP) is a viable strengthening strategy, yet effective force transfer between concrete and steel remains a key challenge. This paper aims to investigate the retrofitting of reinforced concrete (RC) beams using EBSP through a combined experimental and numerical approach. The study seeks to clarify the mechanisms governing force transfer from concrete to steel, focusing on how surface preparation, adhesive bonding, and mechanical anchoring affect flexural performance. Five small concrete beams and six medium-sized RC beams were strengthened with epoxy-based adhesives and mechanical connectors to enhance the interface between concrete and steel. Quasi-static monotonic three-point bending tests were conducted to capture the force-displacement responses under various conditions, including different plate attachment methods, concrete and steel surface preparations, and the incorporation of mechanical anchors. The results show that surface preparation and mechanical anchoring substantially improve beam performance. Retrofitted beams achieved up to 30% higher ultimate load capacity than the control beam. ABAQUS numerical simulations closely matched experimental outcomes, thereby confirming the effectiveness of the retrofitting techniques employed in this investigation. This study provides practical design insights into EBSP systems for RC beams, highlighting the importance of mechanical connections in enhancing ductility and load transfer.</p>