Influence of edge sharpness on the strength of square concrete columns confined with FRP composite laminates

This paper presents the experimental and analytical results of the study carried out to investigate the influence of the radius of the cross-sectional corners (edges) on the strength of small scale square concrete column specimens confined with FRP composite laminates. The experimental part of the study was achieved by testing 20 specimens under uniaxial compression. Depending on the selected radius of the edges, the section varied from square to circular. Intermediate radii were about 1/6, 1/4, and 1/3 of the side dimension. The sharpest square specimens had a corner radius of 5 mm to make composite application easier and to avoid a premature rupture of the composite. The results show that smoothening the edges of square cross-section plays a significant role in delaying the rupture of the FRP composite at these edges, and the efficiency of FRP confinement is directly related to the radius of the cross-section edges. A modified analytical model is presented to predict the strength of FRP-confined square as well as circular sections. The predicted results are found to be in excellent agreement with the measured ones.