The　finite　element　models　are　established　for　a　reinforced　concrete　frame　structure　with　a　high　aspect　ratio　plane.　This　building　is　the　podium　of　a　complex　commercial　project　located　in　Jinan,　China.　By　inputting　three-way　seismic　waves,　the　structural　fragility　research　is　carried　out　based　on　comparing　the　fragility　curves　with　consideration　on　the　inter-story　drift　and　the　inter-story　torsion　angle　separately　(single-index)　and　comprehensively　(double-index　with　translation-torsion　coupling　effect).　After　adding　buckling-restrained　braces　(BRB)　into　the　structure,　seismic　fragility　analyses　are　done　by　the　same　method.　The　improvements　in　the　structural　seismic　performance　are　investigated,　and　the　contributions　from　BRBs　to　reducing　the　structural　seismic　fragility　are　quantified.　The　results　show　that　the　translation-torsion　coupling　effect　should　be　seriously　considered　in　the　fragility　assessment　of　reinforced　concrete　frame　structures　with　a　high　aspect　ratio　plane.　In　addition,　the　contributions　from　the　BRBs　in　controlling　the　translation-torsion　coupling　effect　and　improving　the　structural　seismic　performance　and　collapse　resistance　are　very　significant.　©　The　Author(s),　under　exclusive　license　to　Springer　Nature　Singapore　Pte　Ltd.　2024.