All about civil construction knowledge- PARAM VISIONS

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👇

👀.  Checklist for column reinforcement./ Points to be checked in column reinforcement.

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 👇

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