An　experimental　investigation　of　a　series　of　three-chord　concrete-filled　steel　tube　(CFST)　built-up　columns　was　conducted　under　eccentric　compression.　The　influences　of　slenderness　ratio,　eccentricity　ratio,　eccentricity　direction,　and　brace　pattern　(battened　or　laced)　on　the　load　bearing　process,　failure　modes,　and　ultimate　load-carrying　capacities　of　the　specimens　were　analyzed.　The　test　results　indicate　that　a　CFST　built-up　column　exhibits　better　performance　than　a　corresponding　plain　steel　built-up　column.　The　ultimate　strengths　and　stiffnesses　of　the　three-chord　CFST　built-up　specimens　decreased　with　increasing　slenderness　ratio　or　eccentricity　ratio.　Battened　specimens　exhibited　lower　load-canying　capacities　than　laced　specimens,　and　different　load-bearing　capacities　were　obtained　for　specimens　under　different　directions　of　compression　eccentricity.　Using　the　proposed　equivalent　slenderness　ratio,　three　existing　design　codes　were　evaluated　to　predict　the　stability　coefficient,　and　a　new　correlation　equation　considering　two　failure　modes　is　suggested　for　calculating　the　ultimate　strength　of　three-chord　CFST　built-up　columns　subject　to　combined　compression　and　flexure.　(C)　2020　Elsevier　Ltd.　All　rights　reserved.