Fibre-reinforced polymer efficiency in square columns with different corner radii

Confinement of concrete columns by means of externally bonded fibre-reinforced polymer composites is a well-established technique for strengthening purposes. The corner effect is one of the most important parameters affecting the polymer composite efficiency in confined square and rectangular columns. In this work, non-linear finite-element analysis was used to investigate the behaviour of polymer-composite-confined square columns considering the effect of the corner radius. To compare the efficiency of polymer confinement for different corner radii, column specimens with corner radius-to-side dimension ratios between 0 and 0.5 were modelled and analysed. The Tsai-Wu failure criterion was used to examine the behaviour of the polymer composite under biaxial stresses. The results showed that increasing the corner radius provided more uniformly distributed confining stresses and also increased the polymer composite rupture strain, which improved its efficiency in confinement. Based on the results, in specimens with sharper corners, the interaction of biaxial stresses, hoop tension and axial compression, according to the Tsai-Wu failure criterion, causes maximum stress at the section corners. This leads to premature rupture of the polymer composite at these parts, thus reducing the efficiency of the composite.