Longitudinal　stiffeners　are　effective　in　improving　the　overall　performance　of　concrete-filled　square　or　rectangular　thin-walled　steel　tubular　columns.　This　paper　is　concerned　with　the　nonlinear　analysis　and　design　of　stiffened　square　stub　columns　under　axial　compression.　The　nonlinear　analysis　is　performed　using　ABAQUS,　a　commercially　available　finite　element　(FE)　program.　Close　agreement　is　shown　between　the　test　and　predicted　results　in　terms　of　the　load-deformation　curves　and　ultimate　strength.　The　column　behaviour　is　investigated　and　discussed　using　this　modelling.　The　limit　of　width-to-thickness　ratio　for　the　sub-panels　and　the　rigidity　requirement　for　the　stiffeners　is　discussed.　The　feasibility　using　existing　design　codes　to　predict　the　load-carrying　capacities　of　the　stiffened　composite　columns　is　also　dealt　with　in　this　paper.　(C)　2009　Elsevier　Ltd.　All　rights　reserved.