A unified formulation for hollow and solid concrete-filled steel tube columns under axial compression

On the basis of the theory of elasticity, a unified formulation is proposed in this paper to predict the composite compressive strength of circular concrete-filled steel tube (CCFST) columns. The formula is obtained from the analytic solution of an elastic composite cylinder under axial compression. The formula is further calibrated by introducing a number of correlation coefficients that are validated by test results. Furthermore, the stability factor of CCFST long columns under axial compression is derived on the basis of the Perry–Robertson formula. The newly derived formulas of stability bearing capacity are applicable for both hollow and solid CCFST columns, which is again validated through comparisons with experimental results. One of the important features of the new formulas is that they provide a unified formulation for both hollow and solid CCFST columns that relates the compressive strength or the stability capacity of a CCFST column and a series of design parameters.