What is the correct definition of development length for a reinforcement bar?

• A. The embedment length required for the bar to achieve its yield strength in concrete.
• B. The distance from the bar end to the edge of concrete cover.
• C. The total length of the bar used in the member.
• D. The length of bar that can be bent without breaking.

Answer: (A)

Development length is the embedment length required for a reinforcing bar to develop its yield strength in concrete. This portion of bar inside the concrete provides enough bond between steel and concrete so that the tensile force in the bar can be fully transferred to the surrounding concrete and the bar can reach its yield. If the embedment is too short, the bond can fail or slip before the bar reaches yield, meaning the bar’s capacity isn’t fully utilized.

The other options aren’t describing this concept: the distance from the bar end to the concrete cover relates to protection and exposure, not strength development; the total length of the bar is simply how long the bar is in the member; and the length that can be bent without breaking refers to bend radius or ductility, not development of tension in concrete.