Experimental and numerical study on flexural behavior of ultra-high-performance fiber-reinforced concrete beams with low reinforcement ratios

Flexural behaviors of reinforced ultra-high-performance fiber-reinforced concrete (UHPFRC) beams were experimentally and numerically investigated in terms of reinforcement ratio. To do this, four UHPFRC beams with different reinforcement ratios (0%–1.71%) were fabricated and tested. Since we focused on the placement technique of the steel reinforcing bars, only a small number of reinforced UHPFRC beams were deliberately considered. Test results indicated that with an increase in the reinforcement ratio, post-cracking stiffness and load carrying capacity were increased, whereas first cracking load was decreased. The cracking behavior was characterized by numerous vertical micro-cracks up to near the peak, followed by crack localization with a gradual decrease in load carrying capacity. The number of cracks and average crack spacing were marginally influenced by the reinforcement ratio. Sectional analysis incorporating a linear compressive model and tension-softening curves obtained from inverse analyses and direct tensile test were performed and verified through comparison with the experimental moment–curvature responses.