Eccentric compressive behaviour of elliptical FRP tube-confined reinforced-concrete columns

Elliptical FRP-tube confined reinforced concrete columns (EFCRCCs) are an emerging form of columns particularly suitable for use where the required resistances differ substantially in the two orthogonal lateral directions. This paper first presents a systematic experimental study on the eccentric compressive behaviour of EFCRCCs, with the main test variables being the initial load eccentricity, the sectional aspect ratio, the bending direction and the fibre orientations of the FRP tube. The test results showed that EFCRCCs possessed excellent structural performance, including ample ductility under eccentric compression; the effects of the key test variables on the eccentric compressive behaviour of EFCRCCs were also clarified. A theoretical model developed for EFCRCCs, with the slenderness effect taken into consideration, is then presented. The theoretical model is shown to provide reasonably accurate and conservative predictions of the load-carrying capacity of EFCRCCs. Using this theoretical model, the effects of stress-strain behaviour of the confined concrete in EFCRCCs on their eccentric compressive behaviour are examined, which provides valuable information for the establishment of an accurate stress-strain model for the concrete in eccentrically loaded EFCRCCs.