Behavior of slender CFST columns reinforced with annular stiffeners subjected to axial loads

Abstract

A concrete-filled steel tubular(CFST) column reinforced with annular stiffeners is an innovative composite member developed to improve mechanical properties. This paper investigates the axial compressive behavior of slender CFST columns reinforced with annular stiffeners through both experimental tests and numerical analysis. Initially, five novel composite columns with different slenderness ratios were tested under axial compression. The failure modes, ultimate bearing capacities, load-displacement response, and strain distributions were systematically compared and analyzed. A validated numerical model for axially compressed slender columns was developed to further explore the axial compression mechanism and assess the influence of relevant design parameters on the axial bearing capacity. Subsequently, a comparative analysis was carried out to examine the applicability of various stability coefficient calculation formulas presented in different design methods for composite columns. Parametric regression analysis was employed to develop predictive formulas for calculating the stable bearing capacity of slender composite columns. The results demonstrate that the arrangement of the annular stiffeners causes a rapid increase in the contact stress between the curved steel plate and the concrete once the column reaches its yielding load, thereby promoting the composite action. The proposed calculation formula was proven to possess high accuracy in determining the axial bearing capacity of the slender composite columns.