The effectiveness of CFRP materials strengthening of eccentrically compressed reinforced concrete columns

In the paper the investigations of load-bearing capacity of eccentrically compressed reinforced concrete columns strengthened with CFRP strips and sheets are presented. The aim of the conducted researches was to estimate the influence of changeable longitudinal CFRP reinforcement intensity on load-bearing capacity of columns. In the experimental investigations three longitudinal CFRP strengthening intensities were applied - 2.10%, 1.68% and 1.26%. The experimental tests were performed on columns models with cross-section of 200x200 mm and height of 1 500 mm. The investigative members were loaded axially or eccentrically. The eccentric force was exerted in the area of cross-section core (h/12 and h/6 from neutral axis). In the paper the results of experimental studies on load-bearing capacity depending on longitudinal strengthening intensity were presented and discussed. The failure mechanisms were described. The values of failure force and maximum longitudinal strain were given. The application of longitudinal CFRP strips (as external composite strengthening) causes the increase of column rigidity. Additional transverse strengthening implies delay in debonding the strips from concrete. The interaction of both CFRP materials entails the reduction of strains increase velocity which transfers to the increase of load-bearing capacity.