Flexural Behavior of Two-Way Concrete Slabs Reinforced with Hybrid GFRP and Steel Bars: Experimental and Numerical Study

Fiber-reinforced polymer (FRP) bars have gained wide attention due to their high strength, light weight, low cost, non-corrosive properties, and superior durability. Glass-fiber-reinforced polymer (GFRP) bars offer an effective alternative to steel reinforcement, although their limited ductility remains a challenge. To address this issue, hybrid reinforcement systems of two-way slabs have been considered as experimental programs that combine steel and GFRP bars to achieve a balance between strength, ductility, and long-term durability. This study investigates the flexural behavior of two-way slabs reinforced with hybrid steel and GFRP bars. Four slabs of dimensions 1100 × 1100 × 100 mm were prepared and tested, including one control slab (S1) reinforced with steel bars only and three hybrid slabs with varying bar diameters (10 mm, 8 mm) and spacing as key parameters for the proposed study. The experimental results indicate that the balanced hybrid (S2) achieved the highest capacity, reaching 111.11% of the control’s ultimate load and 13.7% higher energy absorption, with a moderate cost reduction. The ductility index decreased from 2.32 in S1 to 1.73 in S2, reflecting the brittleness of GFRP; slabs S3–S4 reached only about 75% of the control capacity and showed lower energy absorption. The result concluded that a balanced hybrid configuration improves strength and energy dissipation while partially mitigating the ductility loss associated with GFRP reinforcement. A nonlinear finite element model was developed using ANSYS 15 and validated through comparison with experimental results to ensure its accuracy. The nonlinear analysis results showed good agreement with the experimental.