Difference between Lap Length and Development Length (Anchorage)

The main purpose of providing reinforcement bars is to transfer the load from member to member. It may be either to another rebar or to concrete.

In Order to successfully transfer the load from one member to another, reinforcement bars need to be firmly tied at both ends so that it can’t be slipped away.

All the extensions or extra lengths provided in reinforcement has the same purpose.

” To transfer the load safely to another member without any fail”

Are you clear about that? Fine.

Lap Length

Definition – As the name suggest, 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.

Development Length

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 as shown below (Ld).

Hope you have learned something 🙂

Happy Learning 🙂