Extensive　experimental　and　theoretical　studies　of　large　rupture　strain　(LRS)　fiber-reinforced　polymer　(FRP)-confined　concrete　columns　have　been　conducted　based　on　small-scale　columns,　mostly　with　a　diameter　of　150　mm.　This　paper　presents　the　first-ever　study　on　the　axial　performance　of　LRS　polyethylene　terephthalate　(PET)　and　polyethylene　naphthalate　(PEN)　FRP-confined　large-scale　concrete　columns.　Twenty　PET　FRP-confined　circular　concrete　columns　and　20　PEN　FRP-confined　square　concrete　columns　were　loaded　concentrically.　The　cross-sectional　diameter　or　side　length　ranged　from　100　to　400　mm.　The　effects　of　specimen　size　and　FRP　volume　ratio　on　the　failure　mode,　axial　stress-strain　relationship,　and　dilation　behavior　were　investigated.　The　load-carrying　capacity　and　ductility　of　LRS　FRP-confined　concrete　increased　with　an　increase　of　the　FRP　volume　ratio.　As　the　specimen　size　increased,　the　confinement　efficiency　of　the　FRP　decreased,　resulting　in　a　lower　strength　enhancement.　The　accuracy　of　existing　size-dependent　strength　models　was　also　evaluated　using　the　residual　error.　Furthermore,　a　modified　size-dependent　model　for　LRS　FRP-confined　circular/square　concrete　columns　was　developed,　which　was　shown　to　have　a　more　satisfactory　performance　than　the　existing　models.　The　proposed　model　can　serve　as　a　basic　model　for　the　seismic　analysis　of　strengthened　reinforced　concrete　(RC)　columns　with　LRS　FRP,　with　the　possible　size　effect　duly　accounted.