Concrete Columns Confined with Large Rupture Strain Composites: An Emerging Field

Large rupture strain (LRS) fibre-reinforced polymer (FRP) composites are emerging as a competitive solution for the seismic retrofitting of reinforced concrete (RC) columns. Research on the confinement of concrete with FRP to date has primarily been focused on traditional FRP composites exhibiting ultimate tensile strains generally less than 3%. Such composites are usually made from carbon, glass or aramid fibres. For this reason, existing knowledge of FRP confinement needs to be assessed with the use of LRS FRP composites that possess tensile strain capacities well in excess of traditional FRP materials. Initially, this paper introduces large rupture strain fibres. Then, a summary of existing research on the compressive behavior of LRS FRP-confined concrete columns is provided. The general form of the compressive stress-strain relationship of such confined concrete is bilinear and similar to that of circular columns confined with traditional FRP composites. However, similar to square and rectangular columns insufficiently confined with traditional FRPs, square and rectangular LRS FRP-confined columns exhibit a strength softening region before the FRP activates. It is expected that if the stiffness of LRS FRP confinement materials is increased, then a more traditional bilinear behavior could be exhibited. Finally, recommendations for future research are provided.