Bond Strength on the Interface between Concrete and Steel and Development Length of Reinforcing Bars in RC Structures

For the analysis and design of RC structures, there is a fundamental assumption that the strain in an embedded reinforcing bar is the same as that in the surrounding concrete. Therefore, bond forces must be developed on the interface between concrete and steel, such as to prevent significant slip from occurring at the interface. An end anchorage may be considered reliable if the bar is embedded in to concrete a prescribed distance known as the development length of the bar. If in the beam the actual extended length of a bar is equal to or greater than this required development length, no premature bond failure will occur. Research has indicated that the development length was influenced by tensile strength of concrete, surface and diameter of bar, cover distance, bar spacing, transverse reinforcement, and other factors. Current design methods in different countries’ Codes, attentions are directed toward providing adequate length of embedment, which will ensure development of the full strength of the bar.