Definition – Lap length is provided for overlapping two rebars in order to safely transfer the load from one bar to another bar.
We know that rebars come in a certain length. If the rebar needs to be extended beyond that limit then sufficient lap length to be provided to safely transfer the load.
Lap length differs according to tension (at bottom of a beam) and compression zones (at top of beam) and depends upon the grade of concrete, rebar size, concrete cover etc.
Definition – Development Length is provided to transfer the load from steel to concrete. Development Length is also known as anchorage length.
According to IS 456:2000, the calculated tension or compression in any bar at any section shall be developed on each side of the section by providing appropriate development length or by an end anchorage. So that the member won’t be slipped away from the support.
Such length will be provided in a continuous beam, cantilever slabs and other critical joints (beam-column). It will be provided as a bend where the restraining member is thin like as an end beam.