Strength and deformability of concrete members wrapped with fibre reinforced polymer composites with a large rupture strain

Recently, a new category of fibre-reinforced polymer (FRP) composites has emerged as a potential alternative to conventional FRPs, whose reinforcing fibres are usually made of carbon, glass or aramid. These new FRP composites are made of Polyacetal fibres (PAF), Polyethylene Naphthalate (PEN) fibres, or Polyethylene Terephthalate (PET) fibres, which are characterised by a large tensile rupture strain (LRS) (usually larger than 5%) and a relatively low elastic modulus. Compared to conventional FRPs, LRS FRPs are much cheaper and more environmentally friendly since they can be made of recycled plastics (e.g. PET bottles). This paper presents a summary of several completed/on-going research projects conducted in the authors’ research groups on the structural performance of concrete members wrapped with LRS FRP composites, including the compressive behaviour of LRS FRP-confined concrete, the deformability of RC columns confined or internally shear-reinforced with LRS FRP composites under seismic loading, and the shear strengthening of RC members with LRS FRP composites. It is demonstrated that, despite their relatively low elastic modulus, LRS FRP composites can become a very attractive option particularly for the seismic retrofit of RC columns. Besides, LRS FRP composites also have a good potential to be used as the internal shear reinforcement in RC members since their use can lead to a ­ductile shear failure.