This　paper　presents　an　experimental　investigation　on　local　buckling　behavior　of　extruded　6000　series　alloy　I-shaped　aluminium　alloy　beams.　A　total　of　10　specimens　with　a　wide　range　of　width-to-thickness　ratios　(4.4-15.0　of　flange,　42.9-73.1　of　web)　of　component　plates　were　divided　into　two　types:　one　with　stiffeners　at　mid-span,　and　the　other　without　intermediate　stiffeners.　Failure　modes,　ultimate　loading　capacities;　load-deformation　responses　and　load-strain　curves　of　the　specimens　were　studied.　Local　buckling　occurred　in　the　top　flange　and　web　of　six　specimens　without　intermediate　stiffeners,　and　shear　local　buckling　occurred　in　the　other　four　specimens　with　intermediate　stiffeners　though　which　developed　a　tension　field.　A　finite　element　model　was　developed　and　validated　against　the　test　results,　which　was　used　for　parametric　analysis　of　24　specimens.　The　investigation　focused　on　the　effects　of　the　intermediate　stiffeners　and　width-to-thickness　ratio　on　the　buckling　strength　of　the　aluminium　alloy　beams.　It　was　found　that　component　plates　with　small　width-to-thickness　ratios　could　make　material　function　to　its　fullest　potential;　And　there　was　a　significant　increase　in　the　post-buckling　strength;　Eurocode　9　underestimated　the　loading　capacity　of　the　specimens　to　be　safe.　For　the　specimens　with　thin　(width-to-thickness　ratio　more　than　40)　web,　the　standards　should　be　especially　enhanced.　Calculation　results　of　the　finite　element　model　consist　well　with　the　experimental　results.　(C)　2016　Elsevier　Ltd.　All　rights　reserved.