Provision of appropriate development is an important aspect of safe construction practices, proper development length in reinforcement bars shall be provided as per the steel grade considered in design otherwise in scenarios where less development length against the required is provided the structures will be prone to encounter failure due to slippage of joints, bonds, anchors & Laps, in such cases the bars will not yield first but the failure will happen at joints & laps prior to yielding of reinforcement bars.
Development length (Ld) = d x σs/τbd
d = Diameter of the bar.
σs = Stress in the bar at the section considered as design load.
τbd = Design bond stress.
Reason for Providing Development Length
To develop a safe bond between the bar surface & the concrete so that no failure due to slippage of bar occurs during the ultimate load conditions.
Also, the extra length of the bar provided as development length is responsible for transferring the stresses developed in any section to the adjoining sections (such as at column beam junction the extra length of bars provided from beam to column).