Flexural and cracking performance of ultra-high performance concrete beams with high-strength steel reinforcements

In this study, the flexural and cracking performance of ultra-high performance concrete (UHPC) beams reinforced with high-strength steel reinforcement (HSSR) is investigated. Four beam specimens, including two UHPC beams and two normal-strength concrete (NSC) beams with different HSSR ratios were tested under flexure. The effect of concrete type and HSSR ratio on the flexural behaviour was evaluated. The failure mode, load-deflection response, stiffness, ductility and strain of the concrete and HSSR were discussed. Test results show that UHPC coupled with HSSR achieved better flexural performance and the ability to limit the development of the crack. The flexural capacity, deflection and stiffness for the UHPC beams were increased but the ductility was decreased as the HSSR ratio increased. The flexural behaviors of UHPC beams were predicted by section analysis. The flexural performance of HSSR-UHPC beams should consider the contribution of steel fibre to the tensile strength. Considering the influence of steel fibre, an equation was proposed to predict the average crack spacing. UHPC beams showed excellent agreement with the experimental results. The maximum crack width of 630 MPa reinforced UHPC beams was calculated by NF P 18-710 in accordance with the test results.