Design and behaviour of concrete-filled cold-formed stainless steel tube columns

This paper presents a nonlinear finite element model to investigate the behaviour and design of axially loaded concrete-filled cold-formed high strength stainless steel tube columns. The study was conducted over a wide range of concrete cylinder strengths from 20 to 100 MPa. The depth of flat portion-to-plate thickness ( d / t ) ratio of the square and rectangular hollow sections ranged from 16 to 96, covering compact and slender sections. The columns had different lengths so that the length-to-depth ratio remained a constant of 3. Nonlinear material models for confined concrete and stainless steel tubes were used in the finite element model. The results obtained from the finite element analysis were verified against experimental results. An extensive parametric study was conducted to investigate the effects of cross-section geometry and concrete strength on the behaviour and strength of the columns. The column strengths obtained from the finite element analysis were compared with the design strengths calculated using the American specifications and Australian/New Zealand standards. A design equation was proposed for concrete-filled stainless steel tube columns. It is shown that the design strengths obtained using the proposed modified equation are more accurate compared to the American and Australian/New Zealand predictions.