Eccentric Compression Performance of Round-Ended CFST Slender Columns with Different Aspect Ratios

The objective of this study is to investigate the behaviour of round-ended concrete filled steel tubular (RECFST) under eccentric compression via tests and numerical analyses. This type of structural member has been utilized in arches and piers due to its advantages of major-minor axis distribution and low fluid resistance. Eleven specimens of RECFST slender columns were tested. The experimental results indicated that the failure mode of the RECFSTs was characterized by global buckling deformation. Finite element (FE) models were then established and benchmarked against the experimental data. Subsequently, the parametric investigations were performed to assess the influences of eccentricity ratio e (0.0-1.0), aspect ratio B/D (1.5-3.0), slenderness ratio lambda (17-43), steel ratio alpha (8%-16%) and strengths of concrete fy (30 MPa-50 MPa) and steel fcu (355 MPa-420 MPa) on the carrying capacity of the RECFST slender columns. Considering distinct major and minor axes of the rectangular CFSTs, the applicability of design methods for rectangular CFSTs to RECFST slender columns was assessed by using the equivalent method. As the B/D increases, design methods tend to yield more conservative results under eccentric loading conditions. Generally, EC4 has demonstrated accurate predictions of the ultimate load for RECFSTs with B/D ranging from 1.5 to 3.0 after being equivalent to a rectangular section.