Constitutive behavior of ultra-high-performance steel fiber reinforced concrete under monotonic and cyclic tension

This paper investigates the constitutive behavior of steel fiber reinforced ultra-high-performance concrete (UHPC) subjected to monotonic and cyclic tension for different fiber volume fractions (0%, 1%, 2% and 3%) and fiber aspect ratios (30, 60 and 80). The acoustic emission (AE) technique is used to monitor the damage progression and unravel the cracking mechanism of UHPC during the loadings process. The experimental results indicate that adding steel fibers could remarkably improve the tensile strength and corresponding peak strain under both monotonic and cyclic loading scenarios. The steel fiber reinforced UHPC exhibits distinct ductile failure mode. Unlike the tensile responses of conventional concrete, an obvious nonlinear part is observed in the pre-peak region which contributes to a significant improvement on both peak stress and peak strain. Furthermore, a much plumper stress-strain curve in the post-peak region is also observed in comparison to that of UHPC without fiber inclusion. It is noteworthy that the addition of steel fibers can evidently alleviate the stiffness degradation during the cyclic tension, implying a retarded damage evolution process. It is also observed from AE results that the specimens with higher tensile strengths have more homogeneous distribution of AE signals showing a smeared cracking pattern, whilst specimens with lower tensile strengths provide more concentrated signal distribution around the main crack. Finally, an elastoplastic constitutive model is developed to predict the stress-strain behavior of UHPC under cyclic tension, which yields a close estimation of available experimental results. •The effect of steel fiber inclusion on the cyclic tensile stress-strain behavior of ultra-high-performance concrete was investigated.•The damage mechanism and the bridging effect of steel fiber were unraveled with the help of acoustic emission technique.•An elastoplastic constitutive model for UHPC was proposed with the plastic strain accumulation and damage evolution taken into account.