Finite Element Study on Shear Resistance Enhancement in Concrete Beams Reinforced with Hybrid Steel-GFRP Stirrups

This paper evaluates the shear performance of reinforced concrete (RC) beams featuring a hybrid shear reinforcement system, combining internal steel stirrups with external glass fiber-reinforced polymer (GFRP) stirrups. The proposed configuration leverages the ductility of steel and the corrosion resistance of GFRP, optimizing material placement for both structural performance and durability. A finite element analysis (FEA) was conducted on six large-scale RC beams to evaluate the influence of transverse reinforcement type (steel, GFRP, hybrid), steel-to-FRP ratio (0.56, 1.78), and hybrid stirrup ratio (0.29%, 0.44%, 0.58%) on shear capacity, failure modes, crack propagation, and load-deformation response. The results demonstrated that, for the same transverse reinforcement ratio, beams with hybrid stirrups outperformed those with only steel or FRP stirrups, exhibiting enhanced stress redistribution and shear strength increases of 8% and 13%, respectively. An increase in the steel-to-FRP ratio from 0.56 to 1.78 resulted in enhanced post-cracking stiffness and a 5% rise in ultimate load capacity. The shear capacity rose by 14% at a hybrid stirrup ratio of 0.58%, accompanied by further improvements in post-cracking stiffness. Stirrup strain results indicated that internal steel stirrups reached their yield point, while external FRP stirrups remained unbroken, demonstrating effective interaction between the two materials. The findings highlight the potential of hybrid stirrup systems for enhancing both the strength and durability of RC beams.