Design of concrete-filled cold-formed steel elliptical stub columns

The present paper reports an experimental and numerical investigation on the behavior of concrete-filled cold-formed steel elliptical stub columns. The test program was performed on four elliptical hollow sections infilled with concrete of three different grades (C40, C70 and C100). Thirteen fixed-ended stub columns were tested and details of test program are described in this paper. The test program was further supplemented with numerical analyses, where finite element model was firstly developed to emulate the compressive behavior observed from the tests and then used to generate more numerical data via parametric studies. The test results together with the numerical data derived herein were compared with the predictions by the current design rules for concrete-filled steel tubular columns with conventional cross-section shapes. The current American Specifications ANSI/AISC 360 and ACI318 as well as the European Code EN1994-1-1 were evaluated. The comparison demonstrated that both American Specifications result in generally conservative and reliable compressive strength predictions for concrete-filled cold-formed steel elliptical stub columns, whilst the predictions by the European Code are accurate but not reliable. New design method considering the confinement effect was proposed herein, which could provide accurate and reliable compressive resistance predictions for concrete-filled cold-formed steel elliptical stub columns.