This　paper　reports　the　investigations　of　experimental　and　numerical　programs　on　the　shear　performance　of　Ushaped　Polyethylene　Terephthalate　(PET)　FRP-retrofitted　RC　beams.　Twelve　RC　beams　were　fabricated　and　tested　under　monotonic　three-point　loading　with　the　test　parameters　being　FRP　strip　width　and　shear　span-toeffective　depth　ratio.　A　comprehensive　analysis　and　investigation　were　conducted　in　terms　of　the　failure　modes,　shear　load　-　deflection　responses,　shear　capacities,　the　strain　evolution　of　FRP　and　stirrups,　and　the　interaction　of　shear　contributions　among　FRP,　stirrups　and　concrete.　Larger　debonding　strains　were　observed　for　PET　FRP.　Five　design　guidelines　and　two　models　available　in　the　literature　were　assessed　against　the　measured　PET　FRP　shear　contribution.　A　modified　model　of　the　shear　contribution　for　PET　FRP　was　developed　and　verified　by　the　test　results.　Finally,　a　finite　element　model　was　established　to　further　understand　the　shear　performance　of　retrofitted　beams,　in　which　the　bond-slip　relationship　between　concrete　and　FRP　was　considered.　The　FE　model　was　validated　by　comparing　the　test　and　FE　results.　The　proposed　FE　model　could　accurately　capture　the　propagation　of　shear　critical　cracks　and　FRP　debonding　failure　for　the　specimens　with　medium　and　large　shear　spans.