Analytical buckling of slender circular concrete-filled steel tubular columns with compliant interfaces

• Analytical buckling loads for CFST columns with compliant interfaces are derived for the first time.
• Analytical buckling loads of CFST columns are calculated for various material and geometric parameters.
• A good agreement between analytical and experimental buckling loads is obtained.
• Material nonlinearity has a pronounced effect for short CFST columns, and a negligible effect for slender ones.
• The results can be used as a benchmark solution.

This paper presents an efficient mathematical model for studying the global buckling behavior of concrete-filled steel tubular (CFST) columns with compliant interfaces. The present mathematical model is used to evaluate exact critical buckling loads and modes of CFST columns for the first time. The results prove that the presence of finite interface compliance may significantly reduce the critical buckling load of CFST columns. A good agreement between analytical and experimental buckling loads of circular CFST columns is obtained if at least one among longitudinal and radial interfacial stiffnesses is high. The design methods compared in the paper give conservative results in comparison with the experimental results and analytical results for almost perfectly bonded layers. The parametric study reveals that critical buckling loads of CFST columns are very much affected by the diameter-to-depth ratio and concrete elastic modulus. Moreover, a material nonlinearity has a pronounced effect for short CFST columns, and a negligible effect for slender ones.