Analytical and experimental flexural behavior of concrete beams reinforced with glass fiber reinforced polymers bars

• Glass fiber reinforced polymers (GFRP) bars were produced in the lab.
• Ten half-scale concrete beams were tested to study flexural behavior.
• Crack widths, deflection, mode of failure and GFRP bar strains were discussed.
• Non-linear finite element analyses was performed and assessed with experimental results.
• Amendments to ACI 440-06 formula for predicting (Ie) were introduced.

This paper presents an experimental, numerical and analytical study of the flexural behavior of concrete beams reinforced with locally produced glass fiber reinforced polymers (GFRP) bars. Glass fiber reinforced polymers (GFRP) reinforcement bars has a lower stiffness than steel reinforcement, which should be accounted for the ultimate and serviceability conditions, including the impact on member deflection and crack widths. The bars are locally produced by double parts die mold using local resources raw materials. A total of ten beams, measuring 120 mm wide × 300 mm deep × 2800 mm long, were cast and tested up to failure under four-point bending. The main parameters were reinforcement material type (GFRP and steel), concrete compressive strength and reinforcement ratio (μb, 1.7 μb and 2.7 μb; where μb is the reinforcement ratio at balanced condition). The mid-span deflection, crack width and GFRP reinforcement strains of the tested beams were recorded and compared. The test results revealed that the crack widths and mid-span deflection were significantly decreased by increasing the reinforcement ratio. The ultimate load increased by 47% and 97% as the reinforcement ratio increased from μb to 2.7 μb. Specimens reinforced by 2.7 μb can produce some amount of ductility provided by the concrete. The recorded strain of GFRP reinforcement reached to 90% of the ultimate strains. A non-linear finite element analysis (NLFEA) was constructed to simulate the flexural behavior of tested beams, in terms of crack pattern and load deflection behavior. It can be considered a good agreement between the experimental and numerical results was achieved. Modifications to ACI 440.1R-06 equation for estimating the effective moment of inertia (Ie) of FRP-reinforced concrete beams, using regression analysis of experimental results, is proposed by introducing empirical factors that effectively decrease the Ie at high load level. The proposed equation is compared with different code provisions and previous models for predicting the deflection. It can proved that the proposed factors gives good estimation for the effective moment of inertia (Ie) works well for FRP-reinforced concrete beams at high load level.