This　paper　presents　results　of　a　first-ever　experimental　study　on　the　axial　compressive　behavior　of　large-scale　square　reinforced　concrete　(RC)　columns　confined　with　polyethylene　naphthalate　(PEN)/terephthalate　(PET)　fiber-reinforced　polymer　(FRP)　composites,　which　is　a　new　type　of　FRP　with　a　large　rupture　strain　(LRS)　of　over　5%.　In　total,　10　large-scale　square　RC　columns　were　tested　under　axial　compression,　including　8　LRS　FRP-wrapped　RC　columns　and　2　RC　columns,　which　served　as　control　specimens.　The　key　experimental　parameters　were　the　sectional　corner　radius　and　the　thickness　and　type　of　LRS　FRP.　The　test　results　show　that　the　effective　confinement　stiffness　ratio　of　an　FRP　jacket,　as　determined　by　the　corner　radius　and　FRP　thickness,　has　a　significant　effect　on　the　axial　compressive　behavior　of　LRS　FRP-jacketed　large-scale　square　RC　columns.　Based　on　the　experimental　results,　this　paper　presents　an　evaluation　of　two　existing　LRS　FRP-confined　concrete　models　for　noncircular　columns.　Finally,　based　on　the　test　findings,　a　refined　model　for　LRS　FRP-confined　large-scale　square　columns　is　presented　to　provide　more　accurate　predictions　of　the　compressive　behavior　of　these　columns.