Mechanical investigation and design of axially-loaded concrete columns reinforced with grade 700 MPa reinforcing bars

The utilisation of high-strength steel rebars is meaningful for saving iron ore resources and reducing engineering costs, which is extremely important for developing a green low carbon society. However, the research on the performance of the concrete column reinforced with rebars over 600 MPa yield stress is quite limited. To fill up this gap, this paper introduces a novel high-strength hot-finished rebar offering yield stress of about 700 MPa (HSR700) and conducts an experimental study of axially-loaded concrete columns reinforced by normal-strength rebars (RC-NSR) and HSR700 (RC-HSR700). Refined numerical modelling is developed and verified by selecting proper concrete models and modifying the element type. Detailed mechanical analyses on the potential failure modes, the confinement state of the concrete and the bending behaviour of the longitudinal rebar are performed to figure out the compatibility behaviour between the concrete and HSR700 bars. A following systemic para-metric investigation is developed to explore the impacts of material and geometric parameters (i.e. the amount of longitudinal and transverse reinforcements) on the axial compression performance of the RC-HSR700 short columns. The research results indicate that the load-bearing capacity and deformation ability of the RC columns evidently increase with the use of HSR700. In respect of the compatibility, the strength utilisation of HSR700 longitudinal bars can be gradually improved by 29.5 % when the volumetric ratio of the transverse reinforcement increases from 0.67 % to 1.26 %, but the utilisation degree hardly correlates positively with the concrete strength. Finally, calculation methods for assessing the deformation feature of the longitudinal reinforcement and the axial compression strength of the RC short columns are presented considering the compatibility behaviour between the concrete and HSR700 bars. The research may offer a scientific basis for the application of RC structures using high-strength rebars.