Rectangular Reinforced Concrete Columns Strengthened with Carbon Fiber-Reinforced Polymer Sheets Using Corner Strip-Batten Method

The objective of this study is to investigate the effect of the recently developed corner strip-batten (CSB) technique on rectangular columns strengthened with carbon fiber-reinforced polymer (CFRP) sheets. In this technique, fiber-reinforced polymer (FRP) battens do not experience any curvature in confining the section, but are stretched as completely flat strips similar to flat coupons. For this purpose, 12 rectangular reinforced concrete (RC) columns, each with a cross section of 110 x 160 mm (4.33 x 6.30 in.) and a height of 500 mm (19.69 in.), were subjected to load eccentricities of 0, 30, 90, and 120 mm (0, 1.18, 3.54, and 4.72 in.). Results showed that the CSB technique improved the performance of rectangular specimens in terms of both axial strength and ductility. However, comparison of the results obtained in the authors' previous experimental study on square RC columns revealed that the improvement (that is, load-carrying capacity and ductility enhancement) gained with rectangular specimens was not as prominent as that obtained with square ones. Finally, comparison of the experimental axial load-bending moment (P-M) interaction diagrams for the strengthened columns and those obtained from the expressions suggested in such different codes as ACI 440.2R, fib Bulletin 14, and CNR-DT 200 R1, showed that the estimates of the codes were conservative when compared to experimental results. Keywords: batten; carbon fiber-reinforced polymer composites; corner strip; load eccentricity; P-M interaction diagram; rectangular reinforced concrete column.