Corner strengthening of square and rectangular concrete-filled FRP tubes

This paper presents the results of an experimental study that investigated the application of a corner strengthening technique to square and rectangular concrete-filled fiber-reinforced polymer (FRP) tubes (CFFTs). Effects of the strengthening technique were investigated through axial compression tests undertaken on a series of CFFT specimens having different corner radii and sectional aspect ratios. The results indicate that the compressive behavior of square and rectangular CFFTs can be improved through corner strengthening, which significantly reduces or completely eliminates temporary post-peak strength softening observed in some CFFTs. The results also indicate that the premature FRP rupture at corners due to stress concentrations can be prevented through sufficient strengthening of the specimen corners. It is found that increasing the amount of corner strengthening leads to an increase in the confinement effectiveness of CFFTs and results in a more uniform confining pressure distribution along specimen cross-section. It is also found that corner strengthening provides a more significant improvement in the compressive behavior of CFFTs with lower original confinement effectiveness caused by a smaller corner radius or a larger aspect ratio.