Strengthening of Reinforced Concrete Columns with Combined Ultra-High-Performance Fiber-Reinforced Concrete and Glass Fiber-Reinforced Polymer Jacketing

The axial behavior of circular reinforced concrete (RC) columns strengthened with a combined ultra-high-performance fiber-reinforced concrete (UHPFRC) and glass fiber-reinforced polymer (GFRP) jacketing technique was experimentally investigated. Thirteen base column specimens were cast, each 120 mm (4.8 in.) in diameter and 500 mm (20 in.) in height, two strengthened with a 15 mm (0.6 in.) thick UHPFRC jacket, four confined by full and intermittent strips of GFRP composites, six strengthened with a novel technique of combined UHPFRC and GFRP jacketing, and one without any external strengthening. Experimental results showed that specimens confined by the combined strengthening technique recorded average increases of 197% and 252% in load-carrying capacity and energy absorption, respectively, compared to the control column. The galvanized midlayer increased load-bearing capacity by roughly 10% on average. It was also observed that specimens confined by seven intermittent GFRP strips recorded a 17% average increase in load-carrying capacity compared to the specimen with three strips of total equal width. Finally, a previous model adopted for specimens confined by concrete jacketing was modified and verified against the results of present and previous studies.