Optimizing the Percentage Use of Combined CFRP and Steel Tendons to Enhance Flexural Capacity of Unbonded Prestressed Concrete Beams

The use of prestressed concrete beams is a critical element in modern structural design, offering enhanced load-carrying capacity, improved durability, and reduced deflection. Traditionally, steel tendons have been employed in prestressed concrete systems; however, their susceptibility to corrosion and heavy weight presents challenges in long-term performance. In recent years, Carbon Fibre Reinforced Polymer (CFRP) tendons have been proposed as a corrosion-resistant alternative, offering higher tensile strength and lighter weight, but they suffer from low strain capacity and limited bond behaviour with concrete. This study investigates an optimized design for unbonded prestressed concrete beams utilizing a combination of CFRP and steel tendons to overcome the limitations of each material. By integrating the corrosion resistance and lightness of CFRP with the high strain capacity and proven performance of steel, this hybrid system aims to enhance the flexural capacity and durability of prestressed concrete beams. Through a comprehensive series of numerical simulations and experimental tests, the paper explores the mechanical behaviour, load distribution, and failure modes of beams subjected to bending. Results demonstrate that the combined tendon system significantly improves the flexural strength and post-cracking behaviour compared to conventional steel-only prestressed beams. Additionally, the hybrid design reduces maintenance requirements and increases the longevity of the structure. The findings provide valuable insights for the optimized design of prestressed concrete beams, offering a more sustainable and cost-effective solution for modern infrastructure applications.