Comparison of flexure behavior of beams reinforced with glass fiber reinforced polymers (GFRP) and steel bars

This research paper provides an experiment-based and comparative research of the flexural response and failure of the reinforced concrete beam reinforced solely with Glass Fiber Reinforced Polymer (GFRP) bars and with the traditional steel rebars. They were six reinforced concrete beams which were cast and tested under three-point bending and four beams were reinforced with GFRP bars only and two beams were reinforced with Grade 60 steel bars only. Each specimen was cast in M25 and had an under-reinforced and over-reinforced design to investigate their structural behavior at different reinforcement ratios. Two GFRP-reinforced beams (G1 and G2) and one steel-reinforced beam (S1) were modelled as under-reinforced section with reinforcement ratio of 0.8%, two GFRP-reinforced beams (G3 and G4) and one steel-reinforced beam (S2) were modelled as over-reinforced section with a reinforcement ratio of 2.5%. The experimental program was aimed at determining load deflection behavior, cracking behavior, ultimate load capacity and failure modes of the specimens. The experimental values show that, among the under-reinforced GFRP beams, the highest ultimate loads of 90kN were obtained with the cracking loads of 36.5kN, and the ultimate load of 75kN and the cracking load of 36.5kN with the steel under-reinforced beam (S1). Beams with over-reinforcement performed a little worse with the GFRP beams (G3 and G4) having ultimate loads of 87kN as well as cracking loads of 44kN respectively, and the ultimate load of 72kN and the cracking load of 34.5kN with the steel over-reinforced beam (S2). The outcomes demonstrate the higher flexural strength of GFRP-reinforced beams, but they tended to failure through brittle behavior with reinforcement being suddenly broken unlike the ductile behavior of steel-reinforced beams. The flexural capacity and balanced reinforcement limits were considered based on ACI 440.1R-15 on GFRP and checked according to the CSA S806 provisions, which made sure that it is consistent with the known international design standards. The results show how GFRP bars are a possible alternative to steel-reinforcement, especially in corrosive atmosphere where the reinforcement should last. GFRP bars, despite their brittle behavior, high strength to weight ratio, corrosion resistance and sustainability advantages, make the use of these bars fit in reinforced concrete structures of a durable nature.