Effect of Damage Severity and Flexural Steel Ratio on CFRP Repaired RC Beams

The study aims to investigate the effectiveness and failure modes of using CFRP-bonded sheets as a flexural repair system for RC beams, considering the effect of pre-repair damage levels and flexural steel design limits. This study investigated two different flexural design criteria: RC beams reinforced with the minimum flexural steel limit (ρmin) and RC beams reinforced with the maximum flexural steel limit (ρmax). Additionally, three pre-repair damage levels were considered: design limit load, steel yield limit load, and failure limit load. The study results showed that the RC beams’ repair effectiveness depends on the ratio of the flexural steel provided. Specifically, the beams with a minimum steel ratio demonstrated a higher capacity restoration of 49% to 85% (corresponding to the pre-repair damage level, i.e., design load to failure load), while beams with a maximum steel ratio only achieved a capacity restoration of 15.3% to 28.4%. Regarding failure modes, the beams experienced an intermediate-induced crack (IC) debonding due to pre-repair flexural cracks. Despite the debonding of the CFRP sheets, the beams still had the ability to withstand loads close to their unrepaired capacity. This indicates the possibility of re-repairing the beams after the CFRP debonding. Overall, the findings of this study can be used in the industry to repair RC beams and girders that have been damaged due to extreme loading conditions or other reasons. By using CFRP externally bonded sheets, the capacity of the structures can be restored regardless of the pre-repair damage level and the flexural steel design criteria.