Effect of Deformation Height and Spacing on Bond Strength of Reinforcing Bars

The effect of deformation pattern on bond strength is studied using I in. (25 mm) diameter machined bars with deformation heights of0. 05, 0.075, and 0.10 in. ( 1.27, 1.91, and 2.54 mm) and deformation spacings ranging from 0.26 to 2.2 in. (6.7 to 56 mm). The combinations of rib height and spacing produce relative rib areas (ratio of projected rib area normal to bar axis to product of nominal bar perimeter and center-to-center rib spacing) of 0.20, 0.10, and 0.05 for each deformation height. Conventional reinforcing bars, with a relative rib area of0.07, are also studied. The effect of deformation pattern is evaluated using beam-end specimens with varying degrees of confinement provided to the test bars. Degrees of confinement are: 1) 2-in. ( (51-mm) cover with confining transverse stirrups, and 3) 3-in. (76-mm) cover without confining transverse stirrups. Bars with 2-in. (51-mm) cover have an initial unhanded length of 1 /z in. (13 mm) and a bonded length of 12 in. (305 mm). Bars with 3-in. (76-mm) cover have an initial unhanded length of 4 in. ( 102 mm) and a bonded length of 8 1 /z in. (216 mm).