The　present　study　is　an　investigation　on　the　behaviors　of　concrete-filled　thin-walled　steel　tubular　members　subjected　to　combined　loading,　such　as　compression　and　torsion,　bending　and　torsion,　compression,　bending　and　torsion.　ABAQUS　software　is　used　in　this　paper　for　the　finite　element　analysis　(FEA).　A　comparison　of　results　calculated　using　this　modeling　shows　generally　good　agreement　with　test　results.　The　FEA　modeling　is　then　used　to　investigate　the　influence　of　important　parameters　that　determine　the　ultimate　strength　of　the　composite　members　under　combined　loading,　such　as　compression　and　torsion,　bending　and　torsion,　compression,　bending　and　torsion.　The　parametric　studies　provide　information　for　the　development　of　formulae　for　calculating　the　ultimate　strength　of　the　composite　members　subjected　to　combined　loading.　(c)　2007　Elsevier　Ltd.　All　rights　reserved.