We use these terms ” Lap Length and Development Length” in Bar Bending Schedule details or drawings, and these two are extensions to the bar. The main purpose of extending bar or adding bar to the existing bar is to transfer the load safely to another bar without any loss.
Lap Length & Development length are extensions of the bar which are done to transfer the load safely to another without any loss.
Lap Length:
From the factory, the length of a steel bar is 12m. If steel bar needs to be increased more than this limit of 12m? Then the two bars are overlapped to transfer the load safely. In Simple, overlapping of two bars to increase the length of the rebar and to transfer load from one rebar to another is known as “Lap Length.” Lap length is different for compression members and tension members
Lap Length for Compression members = 40D Lap Length for Tension members = 50D
In general, Compression members are Columns, and tension members are beams.
Development Length:
In development length, the load carrying by rebar is transferred to the surrounded concrete. Development length is also known as Anchorage Length. Development Length is denoted as Ld Development length is provided in Slabs, Continous beams and at column-beam joints. As per IS 456:2000, in the tension or compression member at any section shall be developed on each side of the section by providing appropriate development length. If provided, the bar won’t be slipped away from the support. It is also provided when a bar carrying certain force is removed. In such cases, it is necessary to transfer this force in the bar to the surrounding concrete over a certain length.
The length of bar required to transfer the force in the bar to the surrounding concrete through bond or length is called “Development length (Ld)”Â
Admin
We use these terms ” Lap Length and Development Length” in Bar Bending Schedule details or drawings, and these two are extensions to the bar.
The main purpose of extending bar or adding bar to the existing bar is to transfer the load safely to another bar without any loss.
Lap Length:
From the factory, the length of a steel bar is 12m. If steel bar needs to be increased more than this limit of 12m? Then the two bars are overlapped to transfer the load safely.
In Simple, overlapping of two bars to increase the length of the rebar and to transfer load from one rebar to another is known as “Lap Length.”
Lap length is different for compression members and tension members
In general, Compression members are Columns, and tension members are beams.
Development Length:
In development length, the load carrying by rebar is transferred to the surrounded concrete. Development length is also known as Anchorage Length.
Development Length is denoted as Ld
Development length is provided in Slabs, Continous beams and at column-beam joints.
As per IS 456:2000, in the tension or compression member at any section shall be developed on each side of the section by providing appropriate development length. If provided, the bar won’t be slipped away from the support.
It is also provided when a bar carrying certain force is removed. In such cases, it is necessary to transfer this force in the bar to the surrounding concrete over a certain length.
Admin
In the below Image of Beam to column junction the development length is clearly mentioned
Admin
As mentioned above lap length is 40d or 50d if a bar diameter is 8mm then the lap length = 40d = 40×8 = 320 mm
The lap length should be 320mm for above case. Hope now you got it
Srikanth Reddy
How to calculate lap lengths?