Many stress-strain models of high strength steel fiber reinforced concrete (SFRC) were proposed to account for major characteristics of SFRC; however, the presence of bond strength between steel fibers and matrix was not considered in most studies. In this study, the bond strength is considered in the proposed stress-strain model. The empirical expressions for determining the proposed stress-strain model are obtained by regressing 61 of stress-strain curves of SFRC. The compression tests on SFRC specimens are also conducted to verify the proposed stress-strain model. In addition, the comparison study between pullout energy obtained from fiber pullout tests and that obtained by using empirical equation are presented, since the bond strength is an important parameter to describe fiber characteristics. By treating steel fibers as confinements, the mechanical properties of SFRC are expressed in terms of reinforcing index, equivalent bond strength, and ultimate compressive stress. The proposed stress-strain model has good agreements with the experimental stress-strain curves obtained either in this study or by other researchers. Furthermore, by considering the bond strength between fibers and matrix and treating steel fibers as confinements, the post-peak behavior of SFRC can be well described and avoid either overestimating or underestimating the post-peak behavior.

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Addition of steel fibers to high strength concrete (HSC) improves its post-peak behavior and energy absorbing capability, which can be described well in term of toughness. This paper attempts to obtain both analytically and experimentally the efficiency of steel fibers in HSC columns with hybrid confinement of transverse reinforcement and steel fibers. Toughness ratio (TR) to quantify the confinement efficiency of HSC columns with hybrid confinement is proposed through a regression analysis by involving sixty-nine TRs of HSC without steel fibers and twenty-seven TRs of HSC with hybrid of transverse reinforcement and steel fibers. The proposed TR equation was further verified by compression tests of seventeen HSC columns conducted in this study, where twelve specimens were reinforced by high strength rebars in longitudinal and transverse directions. The results show that the efficiency of steel fibers in concrete depends on transverse reinforcement spacing, where the steel fibers are more effective if the spacing transverse reinforcement becomes larger in the range of 0.25–1 effective depth of the section column. Furthermore, the axial load–strain curves were developed by employing finite element software (OpenSees) for simulating the response of the structural system. Comparisons between numerical and experimental axial load–strain curves were carried out.

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Conducting research on steel fiber-reinforced concrete (SFRC) beams without stirrups, particularly the SFRC beams with high-strength concrete (HSC) and high-strength steel (HSS) reinforcing bars is essential due to the limitation of test results of high strength SFRC beams with high strength steel reinforcing bars. Eight shear strength prediction equations for analysis and design of the SFRC beam derived by different researchers are summarized. A database was constructed from 236 beams. Accordingly, the previous shear strength equations can be evaluated. Ten high-strength SFRC beams subjected to monotonic loading were prepared to verify the existing shear strength prediction equations. The equations for predicting shear strength of the SFRC beam are proposed on the basis of observations from the test results and evaluation results of the previous shear strength equations. The proposed shear strength equation possesses a reasonable result. For alternative analysis and design of the SFRC beams, ACI 318-19 shear strength equation is modified to consider steel fiber parameters.