ECCENTRIC-LOADED BEHAVIOR OF CIRCULAR RC COLUMNS STRENGTHENED WITH SELF-COMPACTING CONCRETE FILLED STEEL TUBES

According to the tests of 9 strengthened reinforced concrete (RC) columns (1 RC column strengthened by the enlarging cross-section method and 8 RC columns strengthened with self-compacting concrete (SCC) filled steel tubes) and 1 normal RC column under eccentric loading, the bearing capacity, stiffness and ductility of RC columns strengthened by different retrofitting methods were investigated. The influence of eccentricity, steel ratio and compressive strength of SCC on RC columns strengthened with SCC filled steel tubes were also analyzed. Test results show that the bearing capacity and ductility of composite strengthened columns are significantly better than those of the columns strengthened by the enlarging cross-section method. As the eccentricity decreases or the steel ratio increases, the composite strengthened columns show significant increase in the bearing capacity and ductility. The bearing capacity and ductility of composite strengthened columns do not change obviously as SCC strength changes. Based on the stress-strain relationship for concrete and steel, the fiber model is applied to conduct parametric analysis. Results indicate that the N/N_u-M/M_u curves will shrink inwards along with the increment in the steel yield strength or the sectional steel ratio, and expand outwards with the increment in SCC strength or the external diameter of the cross-section of the RC columns.