Prediction of axial compression behavior of rectangular RCFST columns with confining ties

Abstract A numerical investigation has been conducted to predict the peak axial strength, post-peak behavior and confined stress-strain characteristics of reinforced concrete-filled steel tubular (RCFST) columns of rectangular cross-sections under axial compression loading. Finite element analyses are carried out using a computer software ABAQUS to evaluate the axial behavior of RCFST columns. A parametric study has been conducted on rectangular RCFST columns for width-to-depth (aspect) ratios varying between 1 and 2, tube slenderness ratio ranging between 10 and 266), percentage of longitudinal reinforcement varying between 0.87 and 6.21%, five different arrangements of internal ties and volumetric ratios of ties ranging from 0.13 to 3.19%. It is observed that the RCFST columns, even with a slender tube section, showed a significant increase in strength and ductility when effectively confined with internal transverse ties. The results obtained from the numerical study are compared with the analytical confinement models and the design equations of building codes. Based on this study, suitable modifications are proposed for existing design equations to consider the effect of confining reinforcements.