ANALYSIS FOR BEHAVIOR AND ULTIMATE STRENGTH OF CONCRETE CORBELS WITH HYBRID REINFORCEMENT

This research is devoted to investigate the behavior and ultimate strength of concrete corbels with hybrid reinforcement (steel and CFRP) bars subject to vertical distributed applied load only. Experimental investigation were carried on eighteen specimens and divided in two groups according to location of hybrid reinforcement. The experimental program variables include ratio of hybridization, location of hybrid reinforcement, and shear span-to-effective depth (a/d) ratio. All specimens had the same dimensions and tested as upside down double-symmetrical concrete corbels. The experimental program results obtained from the adopted hybridization reinforcement technique showed that a significant improvement in the behavior and carrying capacity of the tested corbels with an increase about (5.6% - 44%), and (2.3% - 20%) in the ultimate load with (a/d) (0.75, and 0.33) respectively, for specimens with main tension hybrid reinforcement with ratio (20, 40, 60, 80, and 100) %. For specimens hybrid in horizontal (closed stirrup) reinforcement, when increase the hybridization ratio of secondary reinforcement from (0 to 50) % and from (0 to 100) %, the ultimate shear strength will increase by about (16%, 10%) and (6.4%, 15.5%) with shear span-to-effective depth ratio (0.75, and 0.33) respectively. The increase in strength and stiffness was realized at the expense of a loss in ductility due to the brittle behavior of CFRP bars. The presence of CFRP bars increased the deflection and crack width at service state, and increased the concrete strain with increasing the hybridization ratio, this was expected due to lower the modulus of elasticity and bond strength of CFRP bars compared with steel bars.