Experimental Study On Constitutive Relationship Of Square Concrete-Filled Steel Tubes Under Compression

Concrete-filled steel tube structure can make full use of the advantages of concrete and steel and the interaction between the two materials,with high bearing capacity,good seismic performance,which is widely used in high-rise building,super high-rise building and urban overpass and other engineering.As a composite component,the steel tube of Concrete-filled steel tube will constrain concrete under the load,while the concrete can also limit the local buckling of the steel tube.Therefore,determining the compressive constitutive relation of the two kinds of materials in the concrete-filled steel tube can better analyze the mechanical performance of the component,and lay a theoretical foundation for the establishment of the finite element model.At present,most of compressive constitutive relation of concrete-filled square steel tube is based on the proposed compressive constitutive relation model of steel tube and concrete which analyses the whole process curve of the components with certain theoretical assumptions.Thus,there are considerable hypotheses and uncertainties for the mechanical properties of concrete and steel tube,as well as the interaction between them.In order to better study the mechanical properties of steel tubes and concrete in Concrete-filled square steel tube,and obtained the compressive constitutive relation of steel tube and concrete.The research work of this paper is carried out.In this paper,the axial compression experiments of six concrete-filled square steel tubular columns with different width-to-thickness ratio and the corresponding size of steel columns and concrete columns were carried out.The results showed that:(1)The test method can be used to separate the axial force of steel tube and concrete in concrete-filled steel tubular column,and get the respective average stress-strain curve of the whole process;(2)From the comparison of the average stress-strain curve of the concrete-filled steel tubular column and the steel tube column,there is considerable difference in late curve form.And when width-to-thickness ratio is larger than a certain value,the peak strength and residual strength of the concrete-filled square steel tubular column are larger than that of the steel column.(3)The axial compressive strength of concrete filled with concrete-filled square steel tubular columns is larger than that of the concrete columns.(4)The axial compressive strength of concrete filled with concrete-filled square steel tubular columns has little change with the increase of width-to-thickness ratio.On the basis of the experiment,this paper compare the ABAQUS simulate analysis of the concrete-filled square steel tubular column and steel column with experimental results to demonstrate the feasibility of finite element modeling,which lay a foundation for the parameters analysis of the concrete-filled steel tubular column.Combining with the existing constitutive relation of concrete-filled square steel tube,the experimental results are compared with Sakino model to analyze the similarities and differences.