Bond decreased drastically at the first cycle, and slowed thereafter, see Fig.4. The bond stresses of unloading branches were approximately 25% lower than that of the loading branch of the same cycle. For deformed confined bars, as the displacement increased and the cycling progressed, the concrete portion in front of the bar ribs crushed and sheared; when the load was reversed, large slip occurred before the ribs that were bearing against the concrete and the bond stress again increased.