RC columns longitudinally strengthened via novel EBRIOG technique

Carbon fiber reinforced polymer (CFRP) composites are materials that have been acceptably used for the external reinforcement of structural load carrying elements such as reinforced concrete (RC) columns. When subjected to axial compression loads, columns longitudinally strengthened with CFRP sheets undergo buckling and debonding of their longitudinal CFRP strips as their failure modes. The present study investigates the efficiency of the new technique called externally bonded reinforcement in/on grooves (EBRIOG) on square RC columns strengthened with longitudinal FRP composites when subjected to cyclic axial compression loading, and examines whether EBRIOG delays the buckling and debonding of longitudinal CFRP sheets. Another aspect of the study involves investigation of the influence of the recently developed corner strip-batten (CSB) technique on confining specimens. In the CSB technique, CFRP battens used for transverse strengthening tend to stretch as entirely straight sheets like what occurs with flat coupons, as they do not tolerate any curvature. In order to compare the above-mentioned techniques and the conventional ones, 12 square column specimens (150 x 150 x 900 mm(3)) are subjected to cyclic axial compression. The experiment parameters consist of the method used for longitudinal strengthening and the technique utilized for confining the specimens. The results exhibit improved efficiency of square RC columns (as realized by their peak load, ductility indices, energy dissipation, equivalent damping factor, secant stiffness, and average compressive stress of longitudinal composite sheets) when the EBRIOG and CSB techniques are employed simultaneously. For instance, the column strengthened through the CSB and EBRIOG method exhibits increases of 192 and 72% in its ductility and load carrying capacity, respectively, compared to those of the unstrengthened one.