Strength and Deformation Characteristics of Concrete Beams Reinforced with Glass Fibre Reinforced Polymer Bars

Abstract

This research presents findings from experiments conducted on the strength and deformation characteristics of concrete beams reinforced with Glass Fiber Reinforced Polymer (GFRP) bars and conventional steel bars as control. The mechanical properties of the GFRP bars and steel bars (10mm and 12mm nominal diameter) used were ascertained. A total of seven (7) reinforced concrete (RC) beams measuring 120mm x 200mm x 2000mm were cast, six (6) of which were GFRP reinforced and one (1) was steel reinforced, and were loaded incrementally until failure. Test variables of two concrete grades, C25 and C30, were adopted in conjunction with two tensile reinforcement ratios of 0.7% and 1.13% for the concrete beams. A uniform compression reinforcement ratio of 0.7% was implemented along with a transverse shear reinforcement ratio of 0.65% for all beams. The data gathered were analyzed using theoretical and experimental approach to provide an insight to deformation characteristics of the reinforced concrete beams cast. An estimation for the theoretical failure load from fracture of tension bars were based on a partial factor of safety (γm) of 1.52 for the tensile strength of GFRP. The study examined the deformational behavior including load-deflection response, crack propagation, flexural capacity and failure modes under a four-point monotonic loading test. The experimental results revealed that the GFRP reinforced concrete beams exhibited typical bilinear elastic behavior under static loading with a reduction in stiffness after cracking. The GFRP RC beams failed by sudden concrete crushing due to shear-bond failure, diagonal tension failure in the concrete, and flexural failure in contrast to the steel reinforced concrete beam which failed due to yielding of the steel tension bars. The investigation further highlighted that increasing the concrete compressive strength and the tensile reinforcement ratio of GFRP RC beams significantly improved their structural performance, reducing crack widths and increasing failure loads. GFRP RC beams recorded higher ultimate load capacities and deformations compared to steel-reinforced beams, despite their brittle failure modes. Further aligning with previous research, findings revealed that higher concrete strength leads to a greater number of cracks, but with reduced spacing and narrower widths.