Strain hardening behavior can be observed in steel fiber reinforced concretes under tensile loads. In this paper, a statistical micromechanical damage framework is presented for the strain hardening steel fiber reinforced concrete (SH-SFRC) considering the interfacial slip-softening and matrix spalling effects. With a linear slip-softening interface law, an analytical model is developed for the single steel fiber pullout behavior. The crack bridging effects are reached by averaging the contribution of the fibers with different inclined angles. Afterwards, the traditional snubbing factor is modified by considering the fiber snubbing and the matrix spalling effects. By adopting the Weibull distribution, a statistical micromechanical damage model is established with the fracture mechanics based cracking criteria and the stress transfer distance. The comparison with the experimental results demonstrates that the proposed framework is capable of reproducing the SH-SFRC’s uniaxial tensile behavior well. Moreover, the impact of the interfacial slip-softening and matrix spalling effects are further discussed with the presented framework.

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Characterizing the bond properties of the steel fiber/matrix interface plays an important role in describing the crack bridging effect in steel fiber-reinforced cementitious composites (SFRCC). In this paper, a new interface law considering the residual shear stress is proposed to interpret the slip-softening effects of the steel fiber/matrix interface. Accordingly, a micromechanical crack bridging model for SFRCC is formulated by combining the single steel fiber pullout model with the image analysis-based fiber orientation distribution. Comparisons with the experimental data and the existing models show that the proposed model can well predict SFRCC’s tensile softening behavior. Meanwhile, the decrease rate of the bridging stress, the composite fracture energy, the peak bridging stress and the corresponding peak crack opening displacement (COD) are employed to quantitatively evaluate the crack bridging curves. Finally, the effects of the residual shear stress ratio, the interfacial softening coefficient and the fiber orientation distribution on the crack bridging relation are discussed with the proposed framework.

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