Difference Between Development Length And Lap Length
Development length and lap length are two important terms in civil engineering. In this article, I will discuss the differences between development length and lap length. Let’s get started.
What Is Development Length?
Development length is the length of bar required for transferring the stress into concrete. In simple words, the quantity of the rebar length that is actually required to be embedded into the concrete to achieve the desired bond strength between concrete and steel by producing required stress for the steel in that area.
- The formula for development is given below:
- Development length (Ld) = d x σs/τbd
Where
- d = Diameter of the bar.
- σs = Stress in the bar at the section considered as design load.
- τbd = Design bond stress.
What Is Lap Length?
Lap length is the overlapping length of two bars side by side which gives the required design length. In RCC structure, if the length of a bar is not sufficiently available to make the design length, lapping is done.
Suppose we need to construct a building of 20 m in height. But there is no 20 m single bar available in the market. The maximum length of rebar available in the market is usually 12 m, so we need to join two bars of 12 m to get a 20 m bar.
The lap length varies from member to member.
-
Lap length for tension members = 40d
-
Lap length for compression members = 50d.
- Where d = Diameter of bars.
In the below image, you can see some amount of rebar is left for future construction.
This extra rebar will be needed for tying bars of column. This extra length of rebar is called lap length.
FAQ
What is lap or development length?
Development length refers to the minimum length rebars must extend into adjacent structural elements to properly transfer tensile stresses. Lap length refers to the length rebars overlap where they are spliced together to provide continuity
What is the difference between anchorage length and lap length?
Lap length describes the overlap between two reinforcing bars to transfer the force from one bar to other. Embedement or anchorage length descibes the required length of bars from a specific member to another member
What is the difference between lap splice length and development length?
The lap splice length is the length two rebar pieces must overlap and be tied together to create a bond as if there was no break and the run is “continuous”. So simply put, development is rebar to concrete, and a splice is rebar to rebar. The lengths of both splice and development do vary
What is the difference between development length and overlapping length?
Development length is not depends on the size of steel. overlapping can be defined as the lapping of two steels side by side to up to the design length. It can be defined as the quantity of steel length needed to be place into the column to create the bond strength between the concrete and steel
What is a lap length?
Lap length is the length provided to overlap two rebars (reinforcement) in order to safely transfer load from one bar to another bar and an alternative to this is to provide mechanical couplers. It is also called lap splices. When a bar diameter has to be changed along its length, Lap Length is also required
How do you calculate development length?
What is the thumb rule for development length? The thumb rule is that the development length is 41 times of nominal bar diameter. So, if the bar diameter is 15 mm, the development length is 615 mm (15×41)
