### How to calculate the percentage of steel in the cross sectional area of a column?/Calculating the reinforcement ratio in a column.

As per IS-456, the cross-sectional area of longitudinal reinforcement in columns shall not be less than 0.8%  and should not exceed 6%.

Now, let us find out the percentage of longitudinal steel in the c/s area of a column as shown below.

Given data:

Breadth of column = b = 450mm.

Depth of column = d = 300mm.

Longitudinal corner bars d1= 20T- 4nos.

Longitudinal mid bars d2= 16T- 4nos.

Reinforcement ratio of the column

= Sectional area of steel ÷ Sectional area of column concrete.

= Ast ÷ b × d.

First, we will calculate the sectional area of all the longitudinal bars

Ast = [{4nos × c/s area of 20mm bars } + { 4nos. × c/s area of 16mm. bars }]

=[{4nos. × (π × d12) ÷ 4} + {4nos. ×  (π × d22 ) ÷ 4}]

Here, d1 & d2 are the diameter of particular bar.

Ast = [{4nos. × (3.142 × 202) ÷ 4} + {4nos. ×  (3.142 × 162 ) ÷ 4}]

= [{4nos. × (1256.8) ÷ 4} + {4nos. ×  (804.35 ) ÷ 4}]

=[{1256.8} + { 804.35 }]

= 2061.15 mm2

Reinforcement ratio

= [Ast ÷( b × d)].

= [2061.15 mm2  ÷ (450mm × 300mm)].

= [2061.15 mm2 ÷135000 mm2]

= 0.01526

Go through the article👇

Reinforcement ratio of the column

The percentage of steel in the c/s area of the column

= reinforcement ratio × 100

= 0.01526 × 100

=1.526%

The calculated percentage of steel is between 0.8% & 6%. Hence safe.

Note: The sectional area of lateral ties ( stirrups) is not considered while calculating the percentage of steel in a column section.

For you 👇