BOND OF REINFORCEMENT UNDER CONTROLLED CONFINEMENT

Twelve specimens were tested to determine the local bond stress-slip characteristics of a #6 reinforcing bar embedded in a 3-in. diameter concrete cylinder. Radial confining stress around the concrete specimen and radial deformation, together with bond stress and slip, were assumed to be fundamental variables needed to describe the interface behavior properly. Configuration-independent bond stress-slip relationships for a short five-lug embedded length were obtained for various degrees of confining pressure. Maximum bond stresses could be increased almost threefold by increasing the confinement stress from 500 to 4500 psi at the bar level. Two types of #6 bars with different deformations were investigated.