This　paper　presents　experimental　studies　and　numerical　simulations　of　circular　reinforced　concrete　(RC)　columns　wrapped　with　Polyethylene　Naphthalate　fiber　reinforced　polymer　(PEN　FRP,　a　kind　of　large-rupture-strain　FRP)　and　conventional　CFRP.　A　total　of　seven　columns　were　designed　and　fabricated,　including　a　control　column,　three　columns　strengthened　with　CFRP,　and　three　columns　strengthened　with　PEN　FRP.　All　columns　were　subjected　to　cyclic　lateral　load　and　a　constant　high　axial　load.　The　effectiveness　of　PEN　FRP　strengthening　was　systematically　analyzed　and　discussed　regarding　the　failure　mode,　displacement　ductility,　lateral　cyclic　load-displacement　curve,　stiffness　degradation　and　energy　dissipation　capacity.　The　test　results　indicated　that　the　control　column　exhibited　inferior　ductility　and　peak　lateral　strength,　while　FRP-strengthened　columns　possess　better　energy　dissipation　capacity　and　ductility.　Further　study　found　that　PEN　FRP　was　preferred　to　CFRP　with　similar　tensile　stiffness　in　seismic　strengthening.　Finally,　based　on　the　cyclic　compression　model　of　LRS　FRPstrengthened　concrete,　the　improved　tensile　model　of　FRP-strengthened　concrete,　and　the　cyclic　stress-strain　model　of　reinforcing　steel,　numerical　simulations　for　seismic　performance　were　carried　out　in　OpenSees.　It　was　found　that　the　numerical　simulation　results　of　all　FRP-strengthened　RC　columns　were　in　excellent　agreement　with　the　test　results.　To　better　understand　the　effect　of　FRP　confinement　stiffness　on　the　seismic　performance　of　circular　columns,　parametric　analysis　was　performed.　Results　showed　that　the　numerical　simulations　need　to　consider　the　buckling　of　longitudinal　reinforcement　for　accurately　predicting　the　seismic　behavior　of　FRPstrengthened　columns　of　lower　confinement　stiffness.