Local bond between a reinforcing bar and concrete under high intensity cyclic load

The local bond behavior of single, double, and triple ribbed reinforcing bars in concrete under high intensity cyclic loads was studied. Loading history, confining pressure, number of ribs, and direction of loading relative to the direction of casting were tested. It is shown that loading history with loading amplitude less than about half of the ultimate load does not affect the bond stiffness of the ultimate bond strength. The amount and rate of increase of slip were higher for specimens under reversed cyclic load than for those under repeated load. The confining pressure increases the ultimate bond strength and the ductility, but the bond stiffness remains the same. Elastic axisymmetric finite element analyses were performed on a triple bar embedded in a concrete cylinder. It is found that a proposed local bond slip curve is a useful model for explaining bond slip behavior and that stiffness at various stages of loading can be used for data input for the finite element analysis.