Tests and design of concrete-filled elliptical hollow section stub columns

Similar to concrete-filled tubular columns, void-filling of elliptical hollow sections (EHS) will produce increased strength, stiffness, energy absorption and fire resistance. Stub column tests on unfilled EHS were performed first. Discussions are made on the equivalent diameters in the literature for deriving the yield slenderness limit. An equivalent rectangular hollow sections (RHS) is proposed to derive such a limit for EHS sections in axial compression. An experimental investigation has also been carried out on the behaviour of concrete-filled EHS stub columns. Both normal concrete and self consolidating concrete (SCC) were used in the testing program. Different loading methods were investigated; e.g., loading through steel alone, loading through concrete alone and loading through the whole cross-section. This paper is based on experimental data on carbon steel EHS with an aspect ratio of 2, which is also the only product type currently produced. The load carrying capacity is compared with that predicted using EC4 and CAN/CSA-S16. Proposed design formulae are given.