Analysis of whole loading process of concrete beams reinforced with hybrid rebars allowing for confinement effect

Concrete beams with hybrid longitudinal reinforcements (a combination of steel and fibre-reinforced polymer (FRP) rebars) exhibit superior performance in ductility, stiffness and durability compared with conventional concrete beams. However, most available approaches rely on some empirical assumptions and ignore the slip between longitudinal rebars and adjacent concrete and the confinement effect of steel stirrups on concrete. The purpose of this work was to derive a generic analytical approach to overcome these limitations. The main advantages of the proposed analytical approach are that it requires only the shear friction and bond–slip material properties of concrete beams and can reasonably predict the whole loading process of concrete beams reinforced with longitudinal steel rebars, FRP rebars or a combination of both. A parametric study was also conducted to investigate the effects of stirrups and longitudinal reinforcement on the behaviour of concrete beams. It was found that stirrups have a significant effect on the strength and ductility of concrete beams and hence cannot be ignored in the design of beams.