Performance of concrete-encased CFST stub columns under axial compression

• A finite element analysis on concrete-encased CFST stub columns is developed.
• Full-range response of the load versus deformation relations is analyzed.
• Parametric studies are performed.
• Simplified model for the ultimate strength of the composite column is suggested.

Concrete-encased CFST is a type of steel-concrete composite construction, and has an increasing trend in being used in high-rise building and bridge structures in China. This paper studies the behavior of concrete-encased concrete filled steel tube (CFST) stub columns under axial compression. A finite element analysis (FEA) modeling is developed to analyze the behavior of the composite columns. The material nonlinearity and the interaction between concrete and steel tube are considered. A set of test data are used to verify the FEA modeling. Full range analysis on the load versus deformation relations of the concrete-encased CFST stub columns is presented. The interactions between the outer concrete and the steel tube of CFST, as well as the core concrete and the steel tube of CFST are investigated. The differences of concrete-encased CFST columns, conventional CFST and RC columns are analyzed. A parametric study is then carried out by using the FEA modeling. Finally, simplified formulas are suggested for predicting the ultimate strength of the composite stub columns.