It is very important to know the lap length of reinforcement bars. Lapping is done to increase the length of the steel bar.
In this blog post, we will talk about the lap length of reinforcement bars.
I would also recommend you read about the Difference between Lap Length and Development Length.
Table of Contents
Lap Length:
During the fixing process of reinforcement bars in reinforcement concrete structures, normally, the required length of steel bar is not available, hence lapping is provided.
Lapping is a simple phenomenon in which reinforcement bars overlapped each other. The main purpose of overlapping is to obtain the design length of a steel bar.
Let us assume, we need to construct a hundred feet tall columns. But if we think practically, 100 feet long reinforcement bars are not available in the market. The maximum length of reinforcement bars available in the market is 12 meters only. Hence, we need to provide lapping in the rebar.
Tensile force should be transferred smoothly from one bar to another bar. To overcome this problem, we have to provide a second bar close to the first bar that is discontinued and overlapping is to be done. The overlapping length between these two bars is known as lap length.
In case of rebar need to be extended, slicing is provided to join two steel bars transmitting the forces to the joined bar.
See the image below.
Basic Formulas of Lap Lenth:
Lap length for Tensile Members:
- For flexural tension = Ld or 30d which is more.
- For direct tension = 2Ld or 30d which is more.
Note: The straight length of lapping should not be less than 15d or 20 centimeters.
Lap length for Compressive Members:
The lap length of compressive members should be equal to development length in compression but not less than 24d.
Lap length for Bars of Different Diameters:
When bars of various diameters are spliced, the lapping should be done based on the small diameter bar.
Lap Splices:
Lap splices should not be done if the diameter of reinforcement bars is greater than 36 mm. Bars having a diameter of more than 36 mm should be connected by welding. Welding connections provide stability to the structure.
Lap Length of Basic Structural Members
- Lap length of columns = 45d
- Lap length of beams= 60d
- Lap length of slabs= 60d
Frequently Asked Question:
Standard length of steel bars is 12 meters. Special lengths may be manufactured in the factory via special orders.