Seismic Behavior Of Concrete Columns With CRB735 High Strength And High Ductility Reinforcement Bars

The use of high strength reinforcement can reduce the amount of steel and the carbon emissions of the engineering structure.Four concrete columns reinforced by CRB735 high strength and high ductility longitudinal steel reinforcement and stirrups were tested under cyclic loading to investigate its seismic behavior.And one concrete column with HRB400 normal strength longitudinal steel reinforcement and stirrups as a referring column was also tested.Meanwhile the numerical simulation was carried out by using the finite element analysis software.Effects of axial load ratio,stirrup spacing,reinforcement strength grade and concrete strength grade on the seismic performance of high-strength reinforced concrete columns were obtained,which provided theoretical basis and experimental data for promoting the application of CRB735 high strength and high ductility steel bars in engineering.The main research results of this paper are as following:(1)Four concrete columns reinforced by CRB735 high strength and high ductility longitudinal steel reinforcement and stirrups were tested under cyclic loading to investigate its seismic behavior.And one concrete column with HRB400 normal strength longitudinal steel reinforcement and stirrups as a referring column was also tested.The damage mode of columns,hysteresis curve,ductility coefficient,stiffness degradation,energy dissipation were studied,which provided theoretical basis for promoting the application of CRB735 high strength and high ductility steel bars in engineering.(2)The results showed that the CRB735 high strength and high ductility reinforced concrete columns suffer from compression-flexure failure.Increasing the axial load ratio could improve the bearing capacity of concrete columns with CRB735 high strength and high ductility steel bars,but it would reduce the ductility and deformation capacity,resulting in the decrease of the ultimate displacement.Reducing the stirrup spacing could slow down the cracking of the concrete column and the degradation rate of the strength of the specimen after the peak point,and improve the ductility and deformation capacity of the specimen.Compared with HRB400 reinforced concrete specimens,the bearing capacity of CRB735 reinforced concrete columns was improved,and the deformation capacity of the specimens was slightly decreased.(3)Using the experimental fitting method,the test data were analyzed and sorted out.Firstly,the skeleton curve restoring force model was obtained according to the dimensionless skeleton curve fitting,and then the stiffness degradation law of the hysteresis curve was obtained by fitting the test data points.Finally,the three-line restoring force model suitable for reinforced concrete column with CRB735 high strength and high ductility steel bars was established.(4)The finite element analysis of the seismic performance of concrete columns with CRB735 high strength and high ductility steel bars was carried out.The effects of concrete strength,reinforcement ratio and slenderness ratio on the seismic performance of concrete columns were studied.Increasing the strength of concrete could improve the bearing capacity of the specimens,but it leaded to the decrease of ductility and deformation capacity of the specimen.(5)According to GB50010-2010’ Code for Design of Concrete Structures’ and the standard formulas in American and European codes,the theoretical values of the bearing capacity of concrete columns with CRB73 5 high strength and high ductility steel bars were basically consistent with the experimental values,indicating that the relevant formulas can be used to calculate the bearing capacity of concrete columns with CRB735 high strength and high ductility steel bars,and there is a certain safety reserve.