Theoretical study on local buckling of rectangular CFT columns under eccentric compression

• Local buckling behavior of eccentrically loaded rectangular CFT columns is studied.
• The formulas for critical buckling stress of the steel plates are derived.
• The B/t or D/t ratios are suggested for eccentrically loaded rectangular CFT columns.
• The design recommendations of the steel plates are suggested.

The local buckling of steel plates in rectangular concrete-filled steel tubular (CFT) columns subjected to eccentric compression is investigated based on the energy method. The formulas for elastic local buckling stress of the steel plates in rectangular CFT columns under eccentric compression are derived, assuming that the unloaded edges of the steel plate are elastically restrained against rotation, whereas the loaded edges are clamped. Subsequently, the formulas are calibrated with the experimental results and compared with calculated results by the empirical method, which exhibit good agreement. Then, these formulas are applied to investigate the local buckling behavior of steel plates in eccentrically loaded rectangular CFT columns. It is found that the local buckling stress of steel plates in eccentrically loaded rectangular CFT columns is significantly influenced by the stress gradient coefficients and width–thickness ratios while it is slightly influenced by cross-sectional aspect ratios (D/B). Finally, the reasonable ranges for width–thickness ratios (B/t) and depth–thickness ratios (D/t) at various stress gradient coefficients corresponding to different cross-sectional aspect ratios are suggested for the steel plates in eccentrically loaded rectangular CFT columns. Furthermore, the appropriate relationship for the thickness of the steel plates at various stress gradient coefficients is suggested for the design of rectangular CFT columns under eccentric compression.