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Writer's picturekinjal shah

How to Calculate the Cutting Length of Bars and Determine the Appropriate Lapping Zone in Columns

Updated: Oct 15

1) Column:-


  1. Column is a vertical structural element that primarily carries axial loads from the structure above to the foundation. In reinforced concrete structures, columns are reinforced with steel bars (rebars) to handle both compression and tension forces.

  2. The minimum no of longitudinal bar in rectangular columns and circular column are 4 and 6 respectively.* Longitudinal bar diameter shall not be less than 12 mm.

  3. The minimum dimension of the column should not be less than 200 mm.

  4. The minimum diameter provided to link is 8 mm, if the diameter of the longitudinal bar is less than or equal to 32 mm.

  5. The minimum diameter provides to link is 10 mm, if the diameter of longitudinal bar is greater than 32 mm.* The maximum spacing of links should be 300 mm from center to center.

  6. Nominal cover for longitudinal reinforcement should not be less than 40 mm or less than the diameter of such bar


2) Lapping:-


  1.  Lapping of bars is required when the length of a single reinforcement bar is insufficient to cover the entire height of the column. Lapping involves overlapping two bars to ensure the continuity of the reinforcement. However, the placement of these lapping zones is critical to maintaining the structural integrity of the column.

  2. What is a Lapping Zone?

  3. The lapping zone overlaps two reinforcement bars to transfer the load from one bar to another.* We can divide the column span (L) into 4 part, and each part would be L/4. So we provide lapping middle (L//4 + L/4) = L/2 distance.

  4. Lapping is not given if the dia of bar is more than 36 mm, bars may be welded or coupling.* Lapping length should be between 40d to 50d, where d is the diameter of bar.* The distance between the lapping of two bars should be 1 meter or more.

  5. Lapping should not be provided within a joint and 2D from the face of the beam, where D = (Depth of beam - Bottom cover - Stirrup dia - Main bar dia)

  6. When bars of two different diameters are to be spliced, the lap length should be calculated based on the diameter of the smaller bar.

  7. Lap lengths depend on the bar's diameter and the load type (tension/compression).By following these guidelines, the structural integrity of columns can be maintained, even with the necessary overlapping of reinforcement bars.


By following these guidelines, the structural integrity of columns can be maintained, even with the necessary overlapping of reinforcement bars.



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