Effect of Reinforcing Bar Deformation Pattern on Flexural Ductility

Concern has been expressed that increases in the stiffness of the bond force-slip relationship of reinforcing bars, resulting from increases in the relative rib area (Rr) of the bars, may have a negative impact on the flexural rotation capacity of reinforced concrete beams. To provide a better understanding of the effect of bar deformation pattern on flexural ductility simply supported reinforced concrete beams were tested to determine loading deflection and moment-rotation behavior using both conventional (Rr = 0.069) and high relative rib area (Rr = 0.119) bars. Reinforcement ratios equal to 43 and 68 percent of the balanced reinforcement ratio were used. The test show that a relatively large change in the relative rib area of reinforcing bars has no measurable effect on the distribution of flexural cracks or on the displacement and rotational capacity of beams in which plastic hinges develop.