Experimental study on the structural performance of concrete beams reinforced with prestressed GFRP and steel bars

This study aims to evaluate the flexural behavior of I-shaped cross-sectional steel-fiber-reinforced concrete (SFRC) beams that are reinforced with prestressed glass fiber reinforced polymer (GFRP) and steel rebars (hybrid reinforcement, HR). The results obtained in the experimental tests on these SFRC beams are compared with those of reinforced concrete (RC) beams that include Z-shape stirrups. The geometry of the groups of beams is equal, but the reinforcement configurations are different. The HR system is formed by prestressed GFRP bars and prestressed steel strands, and seeks to achieve a balance between reinforcement effectiveness, durability, ductility, and cost-competitiveness. The GFRP bars have relatively low elasticity modulus, tensile brittle failure, and intense damage under high temperatures, but are not susceptible to corrosion. Pre-stressed steel strands, disposed with adequate concrete cover to decrease their probability to corrosion, have higher modulus of elasticity and ductile failure, guaranteeing the beam's flexural capacity in case of a fire event. The results obtained on four-point monotonic loading tests are presented and discussed, including the load level at service and ultimate limit state conditions, deformability, and failure mode. The influence of hybrid and fiber reinforcement on the structural performance of the tested beams is analyzed. The study demonstrates the efficacy of Z-shape steel stirrups for the beam's shear resistance, and the efficiency of prestressing GFRP and steel reinforcements on the beam's load carrying capacity. It also shows the potential of SFRC for developing relatively lightweight prestressed structural elements without stirrups.