Analysis and design of wide rectangular concrete-filled steel tubular columns under axial compression

Wide rectangular concrete-filled steel tubular (WR-CFST) columns possess high bearing capacity and are convenient for furniture layout, making them suitable for high-rise residential buildings. However, its section width-to-depth ratio is beyond the limit of the code, and the current research is insufficient, which restricts its wide application. Experiments and finite element parameter analysis have been conducted to study the axial compression behavior of WR-CFST columns. The results indicate that the typical failure mode of all WR-CFST columns is bending failure about the weak axis, and WR-CFST columns are more susceptible to weak axis instability compared to square concrete-filled steel tubes. The force mechanism of the specimens shows that the mid-height constraint effect decreases as the section width-to-depth ratio increases. Parameter analysis results indicate that the section width-to-depth ratio negatively correlates with the ductility but has a negligible impact on stability coefficients. The constraint model proposed by Mander can effectively predict the sectional bearing capacity of WR-CFST columns with section width-to-depth ratios ranging from 2 to 4. The verification of the current design codes shows that most codes overestimate the stability coefficient. Based on the parameter analysis in this study, a simplified prediction formula is proposed for the stability coefficients of WR-CFST columns.