A semi-analytical model to predict the pull-out behaviour of inclined hooked-end steel fibres

The residual post-cracking tensile strength of conventional steel fibre reinforced concrete is directly related to both the amount of fibres crossing a crack and the individual pull-out responses of all activated fibres. Therefore, the knowledge of the single pull-out behaviour is essential to understand the uni-axial or bending behaviour of SFRC when it is considered as a full-fledged composite. Since hooked-end steel fibres are considered to be the most suitable fibre type for structural purposes, the need to accurately predict the pull-out response of these type of fibres, is of great practical importance. In this paper, an experimental investigation of the pull-out response of both straight and hooked-end steel fibres is discussed. Based on the obtained experimental data, a semi-analytical model is developed to predict the fibre pull-out behaviour. The ability of the model to deal with different geometrical and mechanical fibre characteristics as well as the influence of orientation, embedded length and matrix compressive strengths, reflects its overall quality.

► The pull-out of different types of fibres embedded in a mortar matrix is investigated.
► The fibre geometry, strength, embedded length and inclination angle affect the pull-out behaviour.
► Increasing the pull-out inclination angle increases the chance of fibre rupture.
► A combination of low strength fibre with high strength matrix enables fibre rupture.
► All observed pull-out curves can be simulated by the proposed semi-analytical model.