Integral method for ultimate load analysis of concrete-filled steel tubular columns

Based on the synthesis method for calculating elastic-plastic ultimate load of concrete-filled steel tubular columns, a new numerical method is put forward. Hypotheses in the calculation only include the cross-section plane hypothesis and the stress-strain relation of steel and concrete with a consideration of the interaction effect between the steel tube and the core concrete, and the assumption on the deformation curve of the original synthesis method is removed. As in this new approach, the elements are divided not only on the cross-section but also along the column length, the balance conditions of multiple cross-sections can be taken into consideration simultaneously. Comparing the original method, the current method is suitable for calculating the ultimate load of not only axial compression columns and eccentrically loaded columns with equal eccentricity, but also eccentrically loaded columns with unequal eccentricity. The ultimate loads of some axial compression columns, eccentrically loaded columns with equal eccentricity and eccentrically loaded columns with unequal eccentricity are computed using the program. And the results show that the present results agree well with experimental and theoretical results in literature.