Abstract：Experiments on seven reinforced concrete (RC) beams strengthened with FRP grid reinforced Ultra High Toughness Cementitious Composite (UHTCC) were conducted to investigate their flexural performance. The types of FRP grid, the reinforcement ratios of FRP grid and the bonding length of the FRP-UHTCC composite layer were selected as the test parameters and the effects of the parameters on the flexural behaviour of RC beams strengthened with FRP-UHTCC were investigated. Based on the test results, the calculation method for the flexural capacity of those strengthened RC beams was proposed. The experimental results showed that there was no relative slip between the FRP-UHTCC composite layer and concrete matrix, so that the debonding failure at the end of reinforced composite layer could be effectively suppressed. The failure mode of the strengthened RC beam was the tensile rupture of partial longitudinal fiber reinforcement in the BFRP grid. The debonding phenomenon between the BFRP grid and UHTCC matrix was not observed, indicating that the bonding is better than that between BFRP textile and UHTCC matrix. The flexural capacity of strengthened RC beam was greatly improved with the increase of reinforcement ratio of BFRP grid. Compared with the RC beam without strengthening, the maximum increases in the cracking, yielding and ultimate limit load of the strengthened beams were 97%, 35% and 33%, respectively. The calculation results showed that the predicted values had good agreements with the test data, implying that the flexural capacity of RC beam strengthened with FRP-UHTCC composite can be effectively predicted.
