Experimental investigation of pre-damaged circular RC columns strengthened with fabric-reinforced cementitious matrix (FRCM)

This paper aims at investigating the efficiency of strengthening pre-damaged circular reinforced concrete (RC) columns with Polyparaphenylene Benzobisoxazole fabric-reinforced cementitious matrix (PBO-FRCM). The investigated parameters were the degree of pre-damage (non-damaged, damaged monotonically up to yielding, or fatigue damaged), the number of PBO-FRCM layers (0, 2, or 4), and the tie spacing (180 or 90 mm). The experimental results of testing 12 short columns under axial compression showed that PBO-FRCM systems enhanced the capacity of the non-damaged columns and successfully restored and further enhanced the capacity of the pre-damaged columns. Columns strengthened with two and four PBO-FRCM layers showed a gain in the capacity of up to 40% and 75%, respectively. Furthermore, PBO-FRCM wrapping enhanced the ductility of both the non-damaged and the pre-damaged columns, in which ductility improvement was more noticeable in columns with the larger tie spacing. Finally, the theoretical load-carrying capacity calculated using ACI 549 provisions showed a good agreement with the experimental capacity of all tested columns.