An Evaluation of the Bond-Splitting Action of Ribbed Bars

Bond action of a ribbed reinforcing bar creates forces that tend to split the concrete cover around the bar. In many practical circumstances, bond strength is limited by the resistance of the member section to these bursting forces. This paper reports on research initiated to examine the relationship between bond strength and bursting forces. Test data show the commonly used assumption that bursting force is directly proportional to bond strength to be incorrect, and that a substantial nonsplitting component of bond strength exists. It is also shown that the confinement provided by the tensile strength of concrete cover is less than generally supposed in analyses of bond strength. A unique relationship between bond strength and bursting forces is proposed, which provides a better representation of experimental observations.