Abstract
This paper presents a nonlinear finite element model to investigate the behaviour of cold-formed steel tubes filled with concrete made with crystallized slag aggregate. The columns had different lengths so that the length-to-depth ratio varied from 0.49 to 24. Nonlinear models for confined concrete and steel welded tubes with taking into account the effect of residual stress of steel section were used in the finite element model. The study was conducted over a wide range of concrete cylinder strengths from 20 to 45 MPa. The depth of flat portion-to-plate thickness (d/t) ratio hollow sections steel ranged from 24 to 52, covering compact and slender sections. The main studied parameters were: the section dimension and the effect of the in filled concrete and its age. 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 Eurocode 4.