Seismic retrofit of square RC columns with polyethylene terephthalate (PET) fibre reinforced polymer composites

This paper presents an experimental study on the seismic retrofit of reinforced concrete (RC) square columns with polyethylene terephthalate (PET) fibre reinforced polymer (FRP) composites, which is a new type of FRP with a larger tensile capacity compared to conventional FRPs. Test results of six PET FRP jacketed specimens are presented and compared with those of a specimen with high strength aramid FRP (HS AFRP) and two reference specimens. Hysteretic responses and failure modes of the specimens under a constant axial load and cyclic lateral loads, as well as the responses of the internal steel reinforcement and the FRP jackets are discussed in detail. The contributions of shear deformation and fixed end rotation due to the slip of longitudinal steel bars to the lateral displacement of columns are also investigated. The results show that PET FRP is a promising alternative to conventional FRPs for the seismic retrofit of RC columns. It improves the displacement ductility of RC columns significantly and does not rupture at the ultimate limit state. Future studies should examine a wider range of geometry and material properties and they should also be concerned with a systematic and direct comparison between specimens jacketed with PET FRP and conventional FRP with equivalent jacket stiffness.

► PET FRP can improve the ductility of RC columns despite its low elastic modulus.
► Ductility of RC columns retrofitted by FRP depends on both its stiffness and its rupture strain.
► No PET fibre rupture occurs at the ultimate state of the retrofitted columns.
► PET FRP is a more economic but efficient solution for seismic retrofit due to its large rupture strain.