Experimental investigation on lightweight concrete-filled cold-formed elliptical hollow section stub columns

• Lightweight concrete-filled (CF) hot-rolled CHS and cold-formed EHS have been investigated.
• 24 stub column test results on hollow and lightweight CF tubes were analyzed.
• Cold-formed EHS showed lower strength and ductility than their parent hot-rolled CHS counterparts.
• Design equations based on EC 4 can be adopted for lightweight CF CHS.
• Simple superposition expression based on EC 4 can be adopted for lightweight CF EHS.

This paper presents an experimental investigation on lightweight concrete-filled circular and elliptical hollow sections under axial compression at cross-section level. The elliptical hollow section (EHS) was cold-formed from the hot-rolled circular hollow section (CHS). Experimental findings, including failure mode, load-deformation history and load carrying capacity, from the 24 stub column tests were compared and reported. Comparisons in particular between the parent hot-rolled CHS and cold-formed EHS were made and stub column results have indicated the cold-forming process decreases both the load carrying capacity and the ductility. Design rules based on European standards were also assessed and assessments have shown that the existing rules can be adopted for the design of lightweight concrete-filled hot-rolled CHS while a simple superposition model can be used for the design of lightweight concrete-filled cold-formed EHS.