Experimental Study On Reasonable Axial Compression Ratio Of Zone-confined Concrete Cylinder

Previous studies have shown that the form of regional constraints can greatly improve the bearing capacity and ductility of components.In terms of compression members,most of the previous studies are aimed at rectangular section columns,and the study of circular section columns is less.It is well known that the seismic performance of columns is affected by many factors,among which the key factors are axial compression ratio,reinforcement form and constraint strength.In this paper,the seismic performance of circular cross-section columns under the influence of axial compression ratio is studied to seek the reasonable axial compression ratio of regionally confined concrete columns and provide a theoretical basis for the application of regionally confined concrete columns in structures.The research work is carried out by six specimens,including two traditional cross-section reinforced cylinders,one core column(cylinder)and three regionally constrained cross-section reinforced cylinders.The structural test and finite element analysis are used to discuss the seismic performance of the cylinder under reciprocating load in the range of axial compression ratio 0.8-1.2,so as to seek the reasonable axial compression ratio of the regionally constrained concrete cylinder.Research shows that:Compared with the traditional reinforced column and core column(column),the regional confined concrete column has higher constraint efficiency and better seismic performance.In the range of axial compression ratio used in the test,the mechanical properties of confined concrete cylinder vary with axial compression ratio:(1)The bearing capacity is basically flat with the increase of axial compression ratio.(2)The ductility increases steadily with the increase of axial compression ratio,and the displacement ductility coefficients are between 3 and 4.(3)The stiffness degradation rate decreases with the increase of axial pressure ratio,and the decrease amplitude gradually decreases.(4)The energy dissipation capacity increases with the increase of axial compression ratio.The results show that the reasonable axial compression ratio of the regional confined concrete column is about 1.1,and it is recommended that the axial compression ratio of the actual project is close to and does not exceed 1.1.