Behaviour of concrete-filled cold-formed elliptical hollow sections with varying aspect ratios

This paper presents the experimental and numerical studies of concrete-filled cold-formed elliptical hollow sections with varying aspect ratios subjected to axial compression load. Twenty one stub columns were tested to investigate the fundamental behaviours of these elliptical concrete-filled steel tubular (CFST) columns. The axial load versus displacement curves, longitudinal and transverse strains in steel tube and failure modes were obtained and discussed. A constitutive model for concrete in the elliptical CFST columns was proposed. Finite element (FE) models were developed and validated against the test results. Parametric studies were carried out to identify the influence of key parameters on the load-bearing capacity. Key parameters included aspect ratio, steel tube to concrete area ratio, yield strength of steel and compressive strength of concrete. Finally, the applicability of relevant design methods to elliptical CFST columns was assessed on the basis of the test and the FE results of this research and other related studies. Results indicated that the design method recommended in the Chinese Standard (GB50936-2014), and the design method for circular CFST columns in EC4 were found to generate accurate predictions.