Experimental study on seismic behavior of high-strength concrete columns reinforced with multiple composite central reinforcement

Eight high-strength concrete columns reinforced with multiple composite central reinforcement were designed and fabricated to conduct research about the construction of a subway station project. Taking the axial compression ratio, stirrup form and stirrup ratio as the main variables, the low-cyclic reversed load tests were carried out to analyze the failure process and failure modes, and the hysteretic behavior, skeleton curve, deformation capacity, stiffness degradation and energy dissipation capacity were systematically studied. The Park-Ang damage model was utilized to analyze the damage evolution law of the columns. Based on the philosophy of performance-based design, the relationships between damage index and damage degree of the column specimens were given. The results showed that the column specimens experienced bending-shear failure and shear failure. With the increase of axial compression ratio, the peak loads increased significantly, but the deformation performance, the ductility, the bearing capacity, the stiffness and the energy dissipation capacity decreased. With the increase of stirrup ratio, the hysteretic loop area of the columns, the ductility and the energy dissipation capacity increased, while the peak load, the bearing capacity and the stiffness degeneration decreased. The change of stirrup type can significantly influence the energy dissipation capacity of the specimens. The hysteretic behavior, deformation performance and energy dissipation capacity of specimen C-DC-100 and C-SC-100 were better, which indicated that these stirrup forms could effectively restrain the concrete in the core area, so the seismic behavior of the columns was improved. The damage indices of all specimens were between 0.17 and 0.35 at the story drift of about 1/50, and no serious damage was observed, which proved the good seismic behavior of high-strength concrete columns reinforced with multiple composite central reinforcement. The columns were destroyed at story drifts from 1/29 to 1/21, and the damage indices of the columns were greater than 1.0. © 2020, Editorial Office of China Civil Engineering Journal. All right reserved.