Experimental Study of Concrete‐Filled Steel Tube Columns With Innovative Cross‐Sectional Shapes

ABSTRACT This work presents an experimental investigation into the axial compression behavior of concrete‐filled steel tube (CFST) columns with innovative cross‐sectional shapes. The newly shaped cross‐sections combine polygonal geometries with inward or outward curved walls, aiming to improve structural performance and architectural space efficiency. A total of 95 short CFST specimens, covering 23 different cross‐sections, were tested under axial loading. Key parameters such as cross‐sectional shape, steel tube thickness, column height, and concrete strength were examined. Results show that outward‐curved walls with smooth corners significantly enhance bearing capacity, ductility, and structural efficiency compared to conventional polygonal sections. In contrast, inward‐curved walls lead to premature failure due to steel–concrete separation. The study provides new insights into the design of high‐performance CFST columns and offers practical recommendations for cross‐sectional optimization.