Rehabilitation of interior reinforced concrete slab–column connections using CFRP sheets

The present work discusses results of an experimental study of interior slab–column connection rehabilitation using carbon fiber-reinforced polymers (CFRP). The objective is to investigate the efficiency of CFRP sheets for rehabilitating and strengthening a flat-plate slab–column connection subjected to monotonic shear and unbalanced moment. The effect of the load eccentricity is selected as the main design parameter for the present study. A series of tests was conducted on six specimens organized in three groups according to the eccentricity of the applied load. The first specimen of each group (control specimen) is loaded up to failure, whereas the load is applied in two steps on the second specimen: during the first loading step, the specimen is loaded up to approximately 70% of the ultimate load of the corresponding control specimen, creating flexural cracks in the tension zone; in the second step, the cracked specimen is reinforced using CFRP sheets bonded on the tension-cracked surface then re-loaded to failure in the second loading phase. The results show that the rehabilitation technique is able to restore and enhance the ultimate load capacity and stiffness of all cracked specimens. However, the ductility index is reduced after rehabilitation even if the failure mode did not change. Furthermore, it is found that the effectiveness of the rehabilitation technique is reduced when the load eccentricity increases.