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

Abstract

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.