Analysis of flexural strength of beam elements reinforced with GFRP bars

The durability of reinforced concrete structures is associated with the strength of both concrete and reinforcement against aggressive environmental factors. Once a crack or local damage to the cover occur in the structure, traditional methods of protecting the reinforcement are no longer functional and the sensitive steel reinforcement is exposed to corrosion and deterioration. Therefore, a composite reinforcement made with fibre-reinforced polymer (FRP) can be a suitable alternative to the traditional reinforcing steel due to its mechanical and physical properties - high corrosion resistance, high tensile strength, electrical and electromagnetic neutrality. The FRP reinforcement is made of continuous fibres immersed in a polymeric resin. The function of the fibres is to provide adequate strength and stiffness of the composite. Whereas the resin is responsible for bonding the fibres with an appropriate distance between them, protecting their surface against damage and transferring stresses to them. For the purposes of this paper, an analysis of the flexural strength of concrete elements reinforced with FRP bars with varying reinforcement ratios was conducted. The tests were performed on six beam elements reinforced with glass fibre-reinforced polymer (GFRP) bars. The beams with dimensions of 0.15x0.2x2.5 m were subjected to 4-point bending. This study aimed to assess the influence of the reinforcement ratio on the flexural strength of concrete beams reinforced with composite bars and to verify the failure mechanisms against the guidelines presented in the standard ACI 440.1R-06. The reinforcement ratio has a significant impact on the failure mechanism and the flexural strength of beam elements reinforced with GFRP bars. An increase in the reinforcement ratio results in an improvement in the flexural strength of the specimen and is likely to change the failure mechanism - from rebar rupture to concrete crushing. The guidelines of ACI 440.1R-06 correctly estimate the flexural strength of the beam elements reinforced with GFRP bars.