Axial behavior of pre-damaged RC columns strengthened with CFRP textile grid-reinforced ECC matrix composites

Abstract

In this study, a high-ductility engineered cementitious composite (ECC) augmented with a high-strength carbon fiber-reinforced polymer (CFRP) grid was newly fabricated to strengthen reinforced concrete (RC) columns with pre-damage. Twenty specimens, including 4 reference specimens and 16 strengthened columns, were prepared. After the pre-application of the predicted loads to produce the designated damage levels, the damaged columns were strengthened with FRP textile-reinforced ECC restraints. The main test parameters included the pre-damage level and the number of CFRP grid layers. The experimental results indicate that the reinforced specimens exhibited satisfactory strengthening, even when the pre-damage level was severe. The ultimate load capacity and ductility increased by 37.7%–72.0% and 21.2%–140.6%, respectively, compared with the corresponding unreinforced reference specimens. However, both the ultimate compressive strength and ductility of the reinforced columns decreased with increasing pre-damage level. Accordingly, a strength prediction model was developed to address the adverse effects of the pre-damage and restraint contributions of the FRP grid, ECC, and hoop reinforcement. The proposed model agrees well with the test results.