Flexural behavior of GFRP and steel bars reinforced lightweight ultra-high performance fiber-reinforced concrete beams with various reinforcement ratios

The synergistic operating mode of the concrete matrix and the reinforcing bar determines the dependability of a structure in complicated environments. The objective of this research has been to provide a comprehensive analysis of the flexural behavior exhibited by lightweight ultra-high performance fiber-reinforced concrete (LUHPC) beams that have been reinforced with high-strength steel bars (HRB500) and glass fiber-reinforced plastic (GFRP) bars. LUHPC was used as the matrix material with a compressive strength of 120 MPa and a density of 2050 kg/m3. This study focused on examining the impact of different reinforcement ratios (0.59 %, 1.27 %, and 1.94 %) and reinforcement types (GFRP and HRB500 bars) about the flexural performance of LUHPC beams under four-point bend loading. As demonstrated by the results of experiments, GFRP-reinforced LUHPC (G-LUHPC) beams with higher reinforcement ratios have higher peak loads, flexural stiffness, and cracking loads but lower ductility. Compared with steel-reinforced LUHPC (S-LUHPC) beams, the bending strength of G-LUHPC beams was reduced by 18.2 %, 24.2 %, and 6.7 %, the peak deflection was increased by 166.5 %, 24.8 %, and 56.9 %, and stiffness degradation and crack development were rapid. After comparing the test results with the current commonly used specifications, it was seen that the codes could better predict the cracking moments and the deflections under service loads of G-LUHPC beams. However, it was noted that both the ultimate moments and the corresponding mid-span deflections were greatly underestimated.