Behaviour of hybrid fibre reinforced concrete beam–column joints under reverse cyclic loads

An experimental investigation was carried out to study the effect of hybrid fibres on the strength and behaviour of High performance concrete beam column joints subjected to reverse cyclic loads. A total of 12 reinforced concrete beams column joints were cast and tested in the present investigation. High performance concrete of M60 grade was designed using the modified ACI method suggested by Aïtcin. Crimped steel fibres and polypropylene fibres were used in hybrid form. The main variables considered were the volume fraction of (i) crimped steel fibres viz. 0.5% (39.25 kg/m3) and 1.0% (78.5 kg/m3) and (ii) polypropylene fibres viz. 0.1% (0.9 kg/m3), 0.15% (1.35 kg/m3), and 0.2% (1.8 kg/m3). Addition of fibres in hybrid form improved many of the engineering properties such as the first crack load, ultimate load and ductility factor of the composite. The combination of 1% (78.5 kg/m3) volume fraction of steel fibres and 0.15% (1.35 kg/m3) volume fraction of polypropylene fibres gave better performance with respect to energy dissipation capacity and stiffness degradation than the other combinations.