Improving the efficiency of FRP-Confined square concrete column by rounding the sharp edges and circularizing the flat sides

This study is carried out to assess a new shape modification technique for the square columns to enhance the effectiveness of the fibre reinforced polymer (FRP) confinement with less enlargement in the cross-sectional size. The technique was implemented by rounding the sharp edges and attaching four precast concrete pieces with a segmental circular shape. A total of 21 concrete specimens were prepared to be tested under uniaxial compressive loading. In addition to the proposed technique, circularization that was suggested by the previous studies and confinement of the square section with rounded corners were implemented for comparison purposes. Furthermore, different confinement scenarios such as full and partial wrapping were conducted. All the specimens were confined with a single layer of the glass FRP (GFRP). The suggested shape modification technique succeeded to enhance the ultimate axial strength and strain of the concrete specimen with less increase in the cross-sectional size. Moreover, the actual rupture strain of the GFRP jacket significantly increased compared with the previous shape modification technique. A theoretical investigation is conducted to validate the experimental results, and good agreement was observed between the test results and the predicted results.