Effect of macro-synthetic and hybrid fibres on the behaviour of square concrete columns reinforced with GFRP rebars under eccentric compression

GFRP rebars have emerged as a suitable alternative for steel rebars to tackle corrosion-related issues. However, the abrupt failure of GFRP-reinforced concrete (RC) elements due to the brittle behaviour of GFRP rebars is a significant concern. Fibre reinforced concrete (FRC) reduces brittleness by providing pseudo-ductility to GFRP RC members failing in compression. Moreover, fibre addition helps reduce crack widths by bridging them when subjected to tensile stresses. The current study aims to understand the influence of adding macro-synthetic Polyolefin (PO) and a hybrid mix of steel and PO fibres (HB) on the behaviour of GFRP-RC columns. Twentysix square columns reinforced with GFRP rebars and discrete fibres are tested. A low-eccentricity to-width ratio (e/d of 0.2) and a high-eccentricity to-width ratio (e/d of 0.4) are chosen as loading parameters. The test matrix includes the following specimens: i) control with no fibres, ii) only PO fibres, and iii) a hybrid mix of steel and PO fibres. Test results show that specimens reinforced with hybrid fibres outperformed macro-synthetic fibres in energy absorption and strength improvement. They also had better post-peak behaviour under eccentric compression. Fibre addition increased the load resistance contribution of GFRP rebars and prevented the complete spalling of concrete cover. It also improved the deformabilty factors when compared to control columns with no fibres under eccentric compression.