Concrete-filled elliptical section steel columns under concentric and eccentric loading

<p dir="ltr">A comprehensive programme of testing of concrete-filled elliptical section steel tubular columns of varying slenderness has been undertaken at Imperial College London. A total of 27 specimens were prepared of varying lengths, including three stub columns, with seven of the tested specimens also possessing steel reinforcement. The specimens were then loaded in compression, either concentrically or with different major axis or minor axis eccentricities. Load, end-shortening, midheight strains, lateral deflection at mid-height and end rotations were measured. These results were then used to validate a finite element model developed in ABAQUS, which incorporated steel material stress–strain properties from tensile testing and a confined concrete model using the measured concrete strengths. The numerical results are shown to agree well with those obtained from the experiments when comparing ultimate load, load–deflection behaviour and failure modes. This allowed a parametric study to be undertaken where the slenderness and load eccentricity of the concrete-filled columns were varied, creating a data set to be used as the basis for developing simplified design rules for inclusion in codes such as Eurocode 4.</p>