Experimental Study On Bearing Capacity Of Short Steel Tubular Column Filled With Steel-reinforced Concrete Under Eccentric Load

With the development of high-rise buildings, the growing height and span of building make columns bear higher and higher axial load. On that condition the columns need to own enough bearing capacity as well as high ductility in prevention of building collapse in big earthquakes. Reviewing the present researches on composite columns, such as those of concrete-filled steel tubular, steel reinforced concrete, steel eccased concrete and so on, another one, i.e. steel tubular column filled with steel-reinforced concrete is introduced in this thesis. Both the insertion of steel section into concrete-filled steel tubular column, and interaction of steel tubular,steel section and concrete, improve the column's bearing capacity,ductility and fire-resistant performance. By experiment and theoretical analysis, the behaviour of composite columns under eccentric compressive loading is researched.The research of this thesis is as follows: firstly, to make a summary of design method of bearing capacity of eccentrically compressed circular or rectangle(square shape) concrete-filled steel tubular columns in both domestic and foreign design regulations. Comparison and analysis have been made about the methods and characteristics of design formulas for the related eccentric compression component supporting capacity. Simultaneously according to the biggest load theory and the simplified built-up column correlation curve, the formula of bearing capacity of eccentrically compressed composite columns is obtained.Secondly, the experiments of short composite columns under eccentric compressive loading are conducted to study the mechanical properties of working feature, ductility and load-carrying capacity. The effects of main factors on these properties are also discussed. The research indicate that the ultimate bearing capacity of the short composite columns calculated by formula agreed well with experimental data.Thirdly, by the analysis of experimental results from short steel tubular columns filled with steel-reinforced concrete and concrete filled short steel tubular columns under eccentric compression, the constitutive relations of the core concrete in composite column are formed. Then, the load-deformation relations numerical analysis models of short composite column subjected to eccentric compressive load is established. The results from load-deformation curves agree well with experimental results.