Experimental investigation on the seismic behaviour of SFRC columns under biaxial bending

Abstract

Research studies on Fibre Reinforced Concrete (FRC) elements have been mostly concentrated on the performance under static loading. Few information are available in literature on the behaviour, analysis and design under seismic loading. In the research work herein presented, four full-scale cantilever columns were tested at the structural laboratory of the University of Canterbury under reversing cyclic lateral loading. Hooked steel fibres were adopted (with a volume fraction, V f = 1%) in the plastic hinge zone to improve the seismic behaviour and reduce damage. Both unidirectional and bidirectional loading protocols were adopted to better simulate the actual response of a column subjected to a ground motion excitation. Test results indicate that fibres can significantly reduce the level of damage typically expected in the plastic hinge zone of a mono- lithic R.C. element. By preventing the cover concrete to spall out at earlier stages and providing some additional anti-buckling restraint to the longitudinal steel bars, remarkable improvements are obtained in the hysteretic response of the element, with proper control on both stiffness and strength degradation. The observed limited damage would result into significant savings in terms of repairing costs and business interruption (downtime). lateral reinforcement for increasing safety against collapse and reduce damage and crack width. Alter- natively, fibres may use to replace part of transverse reinforcement with the main aim to reduce the con- gestion of beam-column joint regions and facilitate construction. The experimental investigations described in this paper represent the beginning of an international joint effort involving several research groups towards the development of a sound basis framework on the seismic design and behaviour of FRC structures. A comprehensive research campaign, involving both experimental and numerical investigations is required and is under planning for the next few years.