The behavior of uni-axially loaded bolt pre-stressing concrete-filled steel tubular short columns

Abstract

Concrete-filled steel tube (CFST) columns have superior strength, stiffness, and ductility than traditional reinforced concrete columns. Despite the above merits, a major issue is that the steel-concrete interface bonding will be impaired by the concrete shrinkage and different lateral dilation of steel and concrete under compression. To mitigate the problem, a bolt pre-stressing CFST column is proposed in this study. Eight CFST columns subjected to axial compression with different magnitudes of pre-constraint and steel tube thicknesses were investigated. The results indicated that the initial stiffness and axial load-bearing capacity were significantly improved after applying bolted pre-constraint, while the improvement degree was related to the pre-constraint magnitude. Subsequently, the confining mechanism of the bolt pre-stressing CFST column was further investigated through numerical analysis. Furthermore, a parametric study was performed, which indicated that increasing the pre-constraint magnitude and the yield strength of the steel tube significantly enhanced the initial stiffness and the axial load-bearing capacity of the CFST column, however, the member ductility weakened. Finally, a calculation formula was proposed to determine the axial load-bearing capacity of the bolt pre-stressing short CFST column with satisfactory accuracy.