Tensile behaviour and moment-curvature relationship of steel fibre reinforced concrete

Conventional concrete reinforced with discrete steel fibres exhibits some unusual behaviour which is not displayed by plain concrete when it is subjected to flexural loading. In this paper, a modified constitutive model for defining the tensile characteristics of the fibrous composite is proposed. Parameters that influence the tensile behaviour of steel fibre reinforced (SFR) concrete are examined. Composite material properties, such as the compressive and tensile strengths (f'(c) and f(t)), fibre volume concentration (V-f), fibre aspect ratio (L/d) and fibre-concrete matrix bond stress (tau(d)), affect the numerical coefficients in the model. Depending on the relative magnitudes of these parameters, the behaviour may exhibit a post-cradling softening or strengthening characteristic. Based on the proposed constitutive model, the full flexural moment-curvature response of SFR concrete is derived and the relationship between tensile and flexural behaviour developed. The calculated flexural response is verified by comparison with published experimental results. Good agreement is obtained for a number of concrete specimens reinforced With different types of steel fibre and different fibre concentrations.