BEHAVIOUR OF M60CONCRETE USING FIBRE COCKTAIL INEXTERIOR BEAM-COLUMN JOINT UNDER REVERSED CYCLICLOADING

The fracture of High Performance Concrete (HPC) occurs in a very explosive manner without previously exhibiting any cracking pattern as a warning. By using special fibre cocktails, (combinations of steel and polypropylene fibres) the explosive failure behaviour of High Performance Concrete (HPC) may be avoided. With the variation of cocktail composition different seismic performance of the material could be adjusted. An experimental programme has been carried out to compare the behaviour of high performance concrete and cocktail fibre reinforced high performance concrete beam column joint under reversed cyclic loading. HPC mix has been designed to obtain a concrete grade of M 60. The mix was designed based on modified ACI 211 method suggested by Shetty [1]. Five numbers of exterior beam-column joints modeled to one fourth of a prototype of a building [2], designed according to Bureau of Indian Standards were cast and tested under reversed cyclic loading. The first specimen was made with high strength concrete and designed as per IS 456:2000 [3] and reinforced accordingly without considering the seismic requirement. The second specimen was made with high strength concrete,designed as per 1893 (Part I) 2002 [4] and reinforcements in the beam-column joint portion was detailed according to IS 13920-1993 [5], for seismic requirements. The remaining three specimens were similar to the first one but various combinations of cocktail fibre concrete in the joint region (constant % (1.5) of steel fibre and 0 to 0.4 % of polypropylene fibre) were used. The cocktail fibre combinations of 1.5% of steel fibre and 0.2% of polypropylene fibre have best performance considering the strength, energy dissipation capacity, and ductility factor. Results indicate that the addition of polypropylene fibre to the steel fibre is optimum for a percentage of 0.2, which have more energy absorbing capacity, less joint rotation, more shear strength, more curvature ductility factor and less reinforcement strain.