Understanding Deflection in GFRP-RC Beams: A Systematic Review of Parameters, Models, and Code Implications

The use of Glass Fiber Reinforced Polymer (GFRP) bars as internal reinforcement in concrete beams has emerged as a viable alternative to conventional steel, particularly in corrosive and aggressive environmental conditions. GFRP offers advantages such as corrosion resistance, low weight, and electromagnetic neutrality. However, its lower modulus of elasticity and linear-elastic behavior result in greater deflection and wider cracks under service loads, raising concerns about serviceability. This study presents a systematic review of experimental, numerical, and analytical research on the deflection behavior of GFRP-reinforced concrete (GFRP-RC) beams. A total of over 20 peer-reviewed studies from 2012 to 2023 were analyzed, focusing on key influencing parameters including reinforcement ratio, span-to-depth ratio, concrete strength, and beam geometry. The performance of current predictive models—especially those from ACI 440.1R-15 and ACI 440.11-22—was evaluated against measured results. The findings show that while existing code models provide practical guidance, they tend to underestimate service-level deflections, particularly in under-reinforced and slender beams. Enhanced analytical methods that incorporate tension stiffening and crack-width-based calculations offer improved accuracy. Limitations of current design provisions and their implications for structural safety and comfort are also discussed. The study contributes to advancing GFRP-RC beam design by identifying key areas for code refinement, including multilayer reinforcement, long-term deformation prediction, and deflection modeling for high-span configurations. Practical implications include safer design solutions for infrastructure in corrosive regions, while research implications suggest the need for broader experimental validation and regional code adaptation. This review supports the development of reliable, serviceable, and sustainable GFRP-RC structures.