Reinforced　concrete　(RC)　bridge　columns　for　skewed,　curved　bridges　and　other　kinds　of　irregular　bridges　can　be　subjected　to　combined　loadings　with　axial　load,　shear　force,　flexure　and　torsion　under　multi-dimensional　earthquake　excitations.　Combined　loadings　including　torsion　probably　affect　the　seismic　performance　of　these　bridge　columns.　The　experimental　investigation　on　the　seismic　performance　of　circular　RC　bridge　columns　under　combined　cyclic　bending　and　torsional　loading　is　conducted　in　this　paper.　Twelve　circular　RC　bridge　column　specimens　are　tested　under　various　loading　conditions:　cyclic　bending,　cyclic　torsion,　and　combined　cyclic　torsion　and　cyclic　bending.　Several　combinations　of　cyclic　bending　and　cyclic　torsion　are　applied　to　evaluate　the　interaction　between　torsion　and　flexural　capacity　of　bridge　columns.　The　experimental　results　showed　that　the　flexural　capacity　decreases　and　the　damage　tends　to　occur　upward　outside　the　flexural　plastic　hinge　region　as　the　level　of　applied　cyclic　torsion　increases,　and　the　torsional　capacity　decreases　as　the　level　of　applied　cyclic　bending　increases.　The　failure　mode　and　deformation　characteristics　of　RC　bridge　columns　will　be　changed　due　to　the　effect　of　combined　flexural　and　torsional　loadings.　The　locking　and　unlocking　effect　of　the　spiral　reinforcement　on　torsional　and　flexural　envelopes　of　columns　under　pure　torsion　and　combined　cyclic　bending　and　torsion　is　found.　The　influence　of　aspect　ratio,　longitudinal　reinforcement　ratio　and　type　of　spiral　reinforcement　on　the　seismic　performance　of　columns　under　combined　action　with　the　same　rotation-drift　ratio　is　also　discussed.　An　empirical　flexural　and　torsional　hysteretic　model　for　circular　RC　columns　with　single　spiral　stirrup　under　combined　cyclic　bending　and　torsion　is　proposed　based　on　the　experimental　results.(C)　2014　Elsevier　Ltd.　All　rights　reserved.