Effectiveness of CFRP Repair on Shear-Damaged Substandard Captive Columns

Abstract

The formation of captive columns is inevitable, especially in the boundary columns of the RC frames due to partial infill walls with the presence of openings. Such captive columns attract an excessive amount of shear forces causing brittle shear failure before attaining the flexural capacity of the column. A substandard RC frame with shear-damaged captive columns was repaired with Carbon Fiber Reinforced Polymers (CFRPs). Then the effectiveness of the applied structural repairing scheme with CFRP sheets was investigated through several response quantities of the tested RC frame. Flexural behaviour dominated the overall response of the bare frame (i.e., without infill wall) through the development of plastic hinges at the column ends. In the second specimen, a partial infill wall with a strip window opening was constructed to enforce the captive column defect. The captive columns were severely damaged by the formation of excessive shear cracks causing a brittle type of behaviour. The second test specimen having excessive shear-damaged columns was then repaired by wrapping the damaged columns with the CFRPs. The partial infill wall was removed from the repaired second specimen not to cause any captive column defect. After repeating the test on the repaired specimen, the former lateral load capacity of the damaged columns was exceeded without experiencing any shear failure. More importantly, the displacement capacity of the repaired specimen was increased considerably by wrapping the damaged columns with CFRPs.