Flexural and serviceability behaviour of macro-synthetic fibre-reinforced concrete beams reinforced with GFRP bars
Hamed Shabani, Alireza Asadian, Khaled Galal
Abstract
Due to the corrosion challenges of conventional steel reinforcement, glass fibre-reinforced polymer (GFRP) bars are used as internal reinforcement in many structural applications. However, due to the lower elastic modulus, the design of GFRP-reinforced concrete structures is primarily governed by the serviceability limits, especially the crack width and deflection. This research addresses these limitations by incorporating macro-synthetic fibres to enhance the flexural performance and serviceability of GFRP-reinforced beams. Eleven concrete beams with varying parameters, including concrete strength, fibre volume fraction, and reinforcement ratio, were cast and tested under a four-point loading scheme. The experimental results were analyzed in terms of crack pattern, deflection, strain in concrete and GFRP bars, crack width, and ultimate flexural capacity. Macro-synthetic fibres significantly improved the flexural performance and serviceability of the beams, reducing deflections and crack widths. The deflection predictions from ACI 440.11–22 code and CSA S806–12 standards overestimated experimental deflections at 0.33 M n by neglecting fibre contributions to tensile stiffness, while the proposed equation achieved better accuracy with a predicted-to-experimental ratio of 1.02 ± 0.05. A new analytical equation provided to determine the stress in the GFRP bars at the service stage, considering the contribution of fibre reinforced concrete (FRC). Increasing the macro-synthetic fibre content up to 0.5 % by volume significantly reduced the bond-dependent coefficient ( k b ), with a reduction of up to 32.8 %. The results indicated that the simplified method, integrating CSA S806–12 and ACI 544.4R-18, yielded more accurate moment capacity predictions, with an average ratio of experimental to predicted ultimate moment capacity of 1.09 and a coefficient of variation of 7.87 %. This research contributes to the existing experimental dataset on GFRP-FRC members and demonstrates the potential of macro-synthetic fibres in addressing serviceability concerns, providing valuable insights for the design and construction of durable concrete structures in corrosive environments.