Constitutive model for steel fibre reinforced concrete in tension

In order to represent the ductile tensile behaviour of steel fibre reinforced concrete (SFRC), the Diverse Embedment Model (DEM) was recently developed, accounting for both the random distribution of fibres and the pull-out behaviour of fibres. Although the DEM shows good agreement with test results measured from uniaxial tension tests, it entails a double numerical integration which complicates its implementation into computational models and software developed for the analysis of the structural behaviour of SFRC members. In this paper, the DEM is simplified by eliminating the double numerical integration; thus, the Simplified DEM (SDEM) is derived. In order to simplify the DEM, only fibre slip on the shorter embedded side is taken into the account of the fibre tensile stress at a crack, while coefficients for frictional bond behaviour and mechanical anchorage effect are incorporated to prevent overestimation of the tensile stress attained by fibres due to the neglect of fibre slip on the longer embedded side. The tensile stress-crack width response of SFRC predicted by the SDEM shows good agreement with that obtained from the DEM; hence, the model's accuracy has largely been retained despite the simplification. In comparisons with test results reported in the previous literature, the SDEM is shown to simulate well not only the direct tensile behaviour but also the flexural behaviour of SFRC members. The SDEM can easily be implemented in currently available analysis models and programs so that it can be useful in the modelling of structural behaviour of SFRC members or structures.