Fibre-reinforced concrete beam assemblages subject to column loss

Application of steel-fibre-reinforced concrete (SFRC) to partially replace conventional steel reinforcement, particularly the stirrups in beams, has found increasing use in practice. However, the collapse response of SFRC beams (with no stirrups) subject to column loss scenario has not been investigated. Accordingly, four 2/5th scale beam sub-assemblages with SFRC and no stirrups are constructed and tested under a column loss scenario and the potential for steel fibres to replace the stirrups is investigated. The experimental results show that the use of structural steel fibres as a replacement for stirrups has a minor influence on the membrane behaviour of beams as well as the robustness of SFRC frames subjected to column loss. In addition, detailed finite-element models of the assemblages are developed and validated against the experimental data and the validated models are used to investigate the influence of steel bar ductility on the ability of beams to develop tensile membrane action. It is concluded that the minimum ductility requirements adopted by the Australian standard for normal ductility reinforcing bars (minimum uniform elongation of 0.05) is not sufficient to allow full development of catenary action in reinforced concrete/SFRC beams.