The　shear　behavior　of　simply　supported　RC　beams　strengthened　with　polyethylene　terephthalate　(PET)　fiber-reinforced　polymer　(FRP)　was　studied　in　this　paper.　The　test　variables　include　strengthening　schemes　(i.e.,　U-wrapping　and　full-wrapping)　and　FRP　reinforcement　ratios.　A　comprehensive　and　meticulous　investigation　was　conducted　on　the　failure　mode　of　RC　beams,　shear　force-deflection　curves,　the　development　process　of　shear　cracks,　the　evolution　of　FRP　strain,　and　the　interaction　between　FRP　and　concrete.　The　shear　capacity　and　deformation　were　increased　by　42.5–123.2%　and　−16.34–96.89%　using　the　fully　wrapped　scheme,　respectively.　The　improvement　in　shear　capacity　was　42.5–72.55%　when　the　U-wrapped　scheme　was　adopted.　The　PET　FRP　fully　wrapped　beams　exhibited　a　type　of　ductile　shear　failure.　The　strain　of　PET　FRP　in　the　fully　wrapped　specimen　exceeded　4%　without　fracture,　ensuring　the　deformation　capacity　after　the　peak　load.　The　shear　deformation　caused　the　increase　in　post-peak　mid-span　deflection.　The　U-wrapped　specimens　showed　debonding　failure,　with　the　debonding　strain　of　PET　FRP　being　more　than　that　of　conventional　FRP.　Finally,　six　design　guidelines　for　PET　FRP　shear　contribution　were　evaluated　for　both　U-wrapped　and　fully　wrapped　schemes.　©　2024　The　Authors