Experimental Study on Flexural Behaviors and Theoretical Compression-Bending Capacity of Unreinforced Steel Fiber Reinforced Concrete

Despite ongoing research efforts aimed at understanding the structural response of steel fiber reinforced concrete (SFRC), there is very limited research on the failure characteristics and theoretical compression-bending capacity of unreinforced steel fiber reinforced concrete (SFRC without rebars, USFRC). In this study, the cube compression tests, notched beam tests, and full-scale segment compression-bending tests are carried out to investigate the flexural performance of USFRC. The crack width–bending moment curves, load–deflection curves, and ultimate load of USFRC segments are obtained. Additionally, the theoretical compression-bending capacity of USFRC segments according to Model Code 2010 is investigated and the calculation methods applicable to different fiber contents, segment sizes, and mix proportions are obtained, which can provide a basis for predicting the performance of USFRC segments in related engineering applications, and some conclusions can be drawn. The results show that steel fibers can slightly improve the compressive strength of concrete, and the improvement capacity varies with different mix proportions and fiber contents. The addition of steel fibers can also improve the compressive failure mode of concrete. The relationships among the crack width, bending moment, and eccentricity can be expressed by a multivariate linear regression equation, and the relationship between the bending moment and deflection can be fitted by a quadratic equation. Both fitting effects are good. Based on the Model Code 2010 calculation model, a calculation method for the compression-bending capacity of USFRC is proposed, and the calculation method of residual tensile strength of steel fiber is modified. The new method can predict the compression-bending capacity of USFRC more accurately.