Steel-fibre-reinforced concrete beams under cyclic loads

The work presented herein is aimed at examining the potential benefits of steel fibres in concrete design. In particular, the shear behaviour of steel-fibre-reinforced concrete (SFRC) beams under cyclic loading was investigated by means of Non-linear Finite-Element Analysis (NLFEA). A key issue assessed is whether the use of steel fibres can result in a significant reduction in conventional reinforcement without compromising ductility and strength requirements. In this respect, the spacing between shear links was relaxed while steel fibres were added to see whether or not the loss of shear strength can be compensated for in this way. This is particularly useful in situations where the shear reinforcement required can lead to congestion of shear links, for instance in seismic design (the critical factor in the latter is the cyclic nature of the load, which is examined in the present research work). The numerical model was calibrated against existing experimental data to ensure the reliability of its
predictions. Parametric studies were subsequently carried out using the full practical range of steel fibre dosages. Statically indeterminate SFRC beams were considered (under both monotonic and cyclic loadings) with increased spacing between shear links. Most of SFRC specimens studied in the literature are focused on determinate beams and information on statically indeterminate beams is sparse. Both axial and transverse loads have been considered which allows for the study of column behaviour as well. The investigations provided insight into how the steel fibres can help reduce the amount of conventional shear links.