This　paper　presents　experimental　and　numerical　investigations　on　the　cross-sectional　behavior　and　compressive　capacities　of　aluminum　alloy　channel　section　stub　columns　after　exposure　to　fire.　A　testing　program　was　performed,　including　heating　tests,　postfire　material　tests,　geometric　imperfection　measurements,　and　16　stub　column　tests.　The　testing　program　was　followed　by　a　numerical　modeling　program.　Finite-element　models　were　developed　to　simulate　the　test　responses　and　conduct　parametric　studies　to　obtain　additional　numerical　data.　The　obtained　test　and　numerical　data　were　analyzed　and　adopted　to　perform　design　analyses,　in　which　the　applicability　of　the　relevant　room-temperature　design　rules　in　the　American,　European,　and　Australian/New　Zealand　codes　to　the　postfire　design　of　aluminum　alloy　channel　sections　under　compression　were　examined.　The　results　of　the　design　analyses　reveal　that　all　three　examined　design　codes　yield　excessively　conservative　and　scattered　predictions　of　postfire　strengths,　owing　to　the　neglect　of　significant　postfire　material　strain　hardening.　Then,　a　new　design　approach　was　proposed　by　rationally　considering　the　material　strain　hardening.　The　new　proposal　was　found　to　offer　greatly　improved　design　accuracy　and　consistency　compared　to　the　American,　European,　and　Australian/New　Zealand　codes,　especially　for　aluminum　alloy　channel　sections　after　exposure　to　elevated　temperatures　above　400°C.　©　2023　American　Society　of　Civil　Engineers.