Experimental and numerical investigations on seismic performance of HTRB630 high-strength steel bars reinforced concrete columns

Heat-treated ribbed bar 630 (HTRB630) is a new type of the main 630 MPa reinforcing steel produced in China. To explore the possibility of using HTRB630 high-strength steel bars to replace HRB400 steel bars in reinforced concrete structures, experimental and numerical investigations on seismic performance of HTRB630 high-strength steel bars and HRB400 steel bars reinforced concrete columns are presented in this article. Firstly, the pseudo-static experiment of HTRB630 and HRB400 steel bars reinforced concrete columns is carried out. Secondly, an efficient modeling method is proposed to simulate and analyze the seismic performance of reinforced concrete columns on OpenSees platform based on the measured mechanical properties. ConcreteCM model and Reinforcing Steel model are applied to accurately simulate the uniaxial constitutive relationship of concrete and steel bars respectively. The constitutive parameters of confined concrete of specimens are calculated using the iterative algorithm method to effectively consider the degree of improvement of concrete performance in the core area by transverse steel reinforcements. Considering the bond-slip effect and shear deformation of reinforcements, a rotation spring element and a shear spring element are introduced on the fiber model. Finally, the applicability and accuracy of the numerical simulation results are verified by the experiment results on the hysteresis curves, normalized skeleton curves, bearing capacity, displacement ductility, energy dissipation capacity and degradation of stiffness. The experimental results indicate that the failure modes of the reinforced concrete column specimens are all bending failure. Hysteresis loops of the specimens reinforced HTRB630 and HRB400 steel bars are all bow-shaped. After the equal strength of HTRB630 steel bars, the shape of the hysteresis curve is not changed significantly. HTRB630 high-strength steel bars reinforced concrete columns can achieve good seismic performance under the premise of reasonable reinforcements. The numerical results indicate that the finite element model has a good simulation effect on most seismic performance indicators. For specimens with relatively low axial pressure and insignificant pinching, the error of the simulated hysteresis curve is larger; for specimens with relatively high axial pressure and obvious pinching, the error of the simulated hysteresis curve is smaller. The simulation errors of those seismic performance indicators are about 10%.