Analysis And Research On Design Of Structural Transformation Methods For Concrete-Filled Steel Tube

In recent years, concrete-filled steel tubular structure is widely used in the tall buildings. As its superiority is not in evidence in the great eccentricity role, concrete-filled steel tubes is often substituted by reinforced concrete column at a certain layer. However, concrete construct measure and attention matters about such conversion are not referred in the existing design and construction regulation of the concrete-filled steel tubular structure. Based on the information of the testing and the theory analysis, switching nodes and conversion principles of concrete-filled tubes between reinforced concrete columns is explored in this paper.By the performance analyses of the various conversion methods of column in practice, the merits and the shortages of these connections are summarized.A series of direct conversion CFST-RC transitional column models are analyzed by nonlinear method utilizing finite element analytic software named ANSYS. These models are established by the direct conversion column ground testing models and based on the size commonly used and restriction of conditions in engineering. Steel pipe to the length of stretch, with hoop rates, raising the length and insert steel axle pressure than for the design parameters to explore different parameters change on force of the transitional column, and the rational design recommendations are put forward.Based on the shear formula of RC column and the analysis of finite element, the laconic formula of the shear capacity of CFST-RC transitional column is brought forward. And the formula on deflection checkup of transitional column is deduced by the method of replacing steel tube with concrete. The calculation methods of the stiffness of concrete-filled steel tubes in different codes are contrasted and summed up. The appropriate formula of the stiffness of CFST to practical project is put forward. Based on the stiffness of CFST and RC, the formula of the stiffness of CFST-RC transitional column is deduced. The force capability of the general framework of CFST and existence CFST-RC transitional column as well as the different conversion sequence CFST framework are compared and analyzed in this paper. The impact of conversion on structure is discussed. CFST changed into RC, which makes the shear and layer-displacement angle of starting the conversion layer and the floor near occurred mutations; the change of the framework in which all conversion occurred in one time is the most obvious, when side columns convert at first, the impact of conversion is the smallest. Therefore, the conversion should be used in symmetrical and margin pillar first conversion.Based on the above analysis, the design advice about conversion structure of CFST is presented, which can be referenced for engineering application and editing criterion.