Hybrid CFRP-steel for enhancing the flexural behavior of reinforced concrete beams

Abstract

Hybrid use of Carbon fiber reinforced polymer (CFRP) composites with conventional construction materials offers an ample opportunity to develop economical and high-performance structures. However, anchoring and debonding problems remains a challenge for the accomplishment of this technique. In this study, a novel application was implemented in which the CFRP sheet was integrated as internal flexural reinforcement for RC beams. The target was to evaluate the contribution of the CFRP sheet to the flexural performance and thus assess the efficiency of using the CFRP sheet as primary or supplemental flexural longitudinal steel reinforcement. CFRP sheet can be cut without difficulty to any width/length and then attaching them to the main steel bars without using epoxy. Similar to the longitudinal steel reinforcement, the CFRP strips work integrally with steel reinforcement as the concrete confines them. The investigated parameters are the number of CFRP layers, CFRP sheet length, strengthening type (internal or external strengthening). Therefore, the feasibility of internal strengthening for improving the behavior of RC beams is of vital interest. The performance of each beam was evaluated in terms of failure mode, load versus mid-span deflection curve, ultimate deflection, ultimate load capacity, stiffness, displacement ductility index, energy absorption, energy absorption ductility index, performance factor, and CFRP strain. The results show a significant improvement in the majority of the investigated parameters and show the effectiveness of internal strengthening. The internal strengthening provided external cracks arresting mechanism and even after reaching the ultimate load capacity.