Effects of Deformation Properties on the Bond of Reinforcing Bars

Abstract

The effects of deformation properties on the bond of steel reinforcing bars to concrete are studied to develop guidelines for commercially produced high relative rib area deformation patterns and accurate equations to predict bond strength. The fundamental behavior of bond is studied using finite element analysis. Beam-end tests are used to investigate the effects of bar size, relative rib area, and the ratio of rib width (measured parallel to the longitudinal axis of the bar) to center-to-center rib spacing on bond strength. 139 specimens containing bars with relative rib areas, R" ranging from 0.05 to 0.28 were tested both with and without transverse stirrups confining the test bar. Bond strength is not affected by Rr for bars not confined by transverse stirrups, but increases as bar size and Rr increase for bars confined by transverse stirrups. Bond strength decreases when the ratio of rib width to center-to-center rib spacing is greater than 0.45. Splice tests are used to investigate the effects of bar size, relative rib area, epoxy coating, and the amount of transverse reinforcement confining the bars on splice strength. Thirty tests of beams containing No. 5 and No. II (16 and 36 mm) bars are combined with sixty-three previously reported tests of beams containing No. 8 (25 nun) bars. The combined results include tests for bars with Rr ranging from 0.065 to 0.140. The results show that splice strength is unaffected by Rr for splices not confined by transverse reinforcement, but increases as bar size and Rr increase for splices confined by transverse reinforcement. Under all conditions of confinement, epoxy coating has a less detrimental effect on the splice strength of high relative rib area bars than on the splice strength of conventional bars. Accurate splice strength equations, that account for the effects of bar size, relative rib area, and epoxy coating on bond strength, are combined with a reliability-based strength reduction factor.