Performance and design of eccentrically-loaded concrete-filled round-ended elliptical hollow section stub columns

Concrete-filled round-ended elliptical hollow section (CFREHS) columns are gradually coming into use as piers and arches in engineering practice, owing to their unique properties concerning aesthetic perception and low flow resistance coefficients. However, there has been a paucity of studies focusing on the structural behaviour and design methods for CFREHS columns. The present study has involved investigating the behaviour of eccentrically-loaded CFREHS stub columns. A nonlinear numerical model that adopts an equivalent stress-strain model for the novel type of confined core concrete was established, and verified via experimental data. Subsequently, the effects of various parameters on the eccentric compressive response of CFREHS stub columns were analysed, including the diameter-to-thickness ratio, load eccentricity ratio, and the cross-section slenderness. Eccentric compressive capacities, failure patterns, strength indexes, stress-strain responses, contact stress, typical force-displacement curves, and M-N curves of eccentrically pressured CFREHS stub columns were also evaluated. The findings of the numerical analysis indicated that the eccentric load bearing capacity of CFREHS stub columns evidently increased for increases in the cross-section area, steel strength, and concrete strength, while the opposite was observed for increases in the load eccentricity ratio and diameter-to-thickness ratio. Finally, simplified empirical formulae were presented to predict the eccentric load bearing capacities of CFREHS stub columns. The results of the study are expected to provide a reliable reference for application to the proposed CFREHS columns in concrete-filled steel tube (CFST) structures.