Investigation of Strut-and-Tie Model Performance Using Symmetrically Loaded GFRP-RC Double Corbels

Corbels are characterized as low shear span-to-depth ratio (a/d) members that transfer vertical and horizontal loads to adjacent members such as columns or walls. Glass fiber-reinforced polymer (GFRP) reinforcement has linear-elastic behavior and a lower modulus of elasticity relative to steel leading to deeper and wider cracks, which is especially critical for low a/d members. Currently, Canadian bridge and building standards provide strut-and-tie modeling provisions to design steel- and GFRP-reinforced concrete (RC) corbels, but the United States (US) code for GFRP-RC structures prohibits the use of this method for GFRP-RC corbels because of lack of research. Eight full-scale GFRP-RC corbels were constructed and tested to failure. The test variables included main tie and secondary reinforcement ratios, a/d ratio, and concrete strength. The experimental results indicated that a/d and concrete strength have a considerable influence on concrete crack width development, deflection, and load-carrying capacity. The Canadian standard for FRP-RC buildings provided conservative shear capacity predictions for all eight corbels. The US code for steel-RC structures overestimated the shear capacity predictions for seven of the eight corbels, suggesting that revisions are required to better predict the capacity of GFRP-RC corbels.