Lap and Anchorage of Reinforcement Bars

Knowing the correct lap lengths and anchorage lengths are very very important when reinforcements are detailed. Inadequate anchorages and lapping have led to many failures of structures in the world. This is mainly due to a lack of attention to small things that many do not consider as important facts.

According to BS 8110 Part 01 1997, we can do our details in a very simple manner without making our life complicated. It has given a simplified table that can be applied to most of the cases.

However, when we do specific details, it is better to go ahead with the first principles rather than rely on the simplified table given in the code.

Code also provides the method to calculate the bond length requirements. We can use either method for detailing the reinforcements.

The following table can be used to find the rebar lapping and anchorage length according to the types of bars are used and the grade of the concrete.

This table is most commonly used by the details due to simplicity. If we know the types of reinforcement are used and the grade of the concrete, we can find the lap and anchorage lengths.

For example, assume we are used deformed type 2 bars and grade 30 concrete.
According to the  table

Compression anchorage length = 32 times bar diameter
Tension anchorage length         = 40 times bar diameter

Similarly, we can find the lap and anchorage lengths from grade 25 to grade 40 concrete.