Let us consider an RCC column of size **380mm. x 230mm.** as shown below.

Now, we need to replace the main bar of 16mm. dia. with 12mm. bar due to its non-availability on-site.

__Given data:__

Main bar dia = 16mm.

No. of bars = 4nos.

**Calculation:**

The sectional area of 16mm. bar

=[ π x d² ➗ 4]

= [3.142 x 16² ➗ 4]

= [804.352 ➗ 4]

= **201.088 mm².**

The sectional area of the total no. of main bars

= [sectional area of 1 bar** **x no. of bars]

= [201.088** **x 4nos.]

= **804.35mm².**

Now, the sectional area of 12mm. bar

=[π x d² ➗ 4]

= [3.142 x 12² ➗ 4]

= [452.448 ➗ 4]

= **113.11 mm².**

No. of 12mm. bars required for replacement

= [Total sectional area of existing bar ➗Sectional area of a single replacing bar]

= [804.35mm².➗ 113.11 mm²]

= **7.11 nos.**

By rounding off = **8 nos.**

**Note**:

1. Always we have to round off the total no. of bars to the upper value.

2. To maintain symmetry, we cannot provide an odd no. of bars in columns.

Therefore, **we have to provide 8nos. of 12mm. bars.**

**Note:**

1. The replacement of bars is uneconomical, as we need to maintain symmetry in columns.

2. Again, we need to provide extra stirrup for a higher no. of replaced bars**.**

3. The replacement is only thought-out when there is a time constraint to complete the project.

**Thank you for going through these calculation steps❤. Have a good day 😄.**

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