Design of a column./ How to design the diameter & no. of reinforcement bars required in a column?/ How to calculate the dia. & no. of bars in a column?

 Eg:

Calculate the diameter & no. of steel bars required in a column of dimension 225mm. x 300mm. The column has an axial load of 570KN. M25 grade concrete & Fe-415 steel are used in the column.

Given data:

Axial load over column = 570KN = 570 x 10³N

Column size = 225mm. x 300mm.

Characteristic compressive strength of concrete=fck=25N/mm²

Yield strength of steel = fy= 415 N/mm².

Calculation:

Ⅰ. Longitudinal reinforcement:

As per IS code

Pu = [0.4 x fck x Ac + 0.67 x fy x Asc] -----------①

Where,

Pu = Ultimate factored load 

     = [factor of safety x axial load over column]

     = [ 1.5 x 570 x 10³N]

 Pu = 855 x 10³N.

Ac = Sectional area of concrete

      = [Ag - Asc]

Here,

 Ag = Gross sectional area of the column

       = [225mm. x 300mm.]

       = 67,500mm²

Asc = Sectional area of steel =?

Putting all the values in formula ①

    Pu = [0.4 x fck x (Ag- Asc) + 0.67 x fy x Asc]

 855 x 10³ = [0.4 x 25 x (67,500- Asc) + 0.67 x 415 x Asc]

855 x 10³ =[6,75,000 - 10Asc + 278Asc]

855 x 10³ = 6,75,000 +268Asc

268Asc = [8,55,000 -6,75,000]

268Asc = 1,80,000

Asc = [1,80,000 ➗ 268]

    Asc = 671.6 mm²

Let us provide a minimum size diameter bar as per IS code, i.e. 12mm.

The sectional area of 1 bar 

=[ π x d² ➗ 4]

= [  3.142 x 12² ➗ 4]

= [452.448 ➗ 4]

= 113.11 mm².

No. of rebars required

= [Asc ➗ area of 1 bar]

= [671.6 ➗ 113.11]

= 5.94 nos. 

By rounding off, the no. of bars required = 6nos.

Now, 

 The actual sectional area of steel

   = [6nos. x 113.11]

   = 678.66 mm².

Ⅱ. Transverse reinforcement:

1. Stirrup ( lateral tie) diameter:

As per IS code,

The diameter of lateral tie bars should be at least 1/4th the dia. of the main bars.

i.e. = [1/4 x 12mm.]

      = 3mm.

So, we can provide a 6mm. or 8mm. dia. lateral tie which is > 3mm., & hence safe.

2. Spacing of stirrup:

The c/c spacing of lateral ties shall not be more than the least of the following three criteria.

a. The least sectional dimension of the column 

      = breadth of the column 

      = 225mm.

b. 16 times the smallest dia. bar of the longitudinal reinforcement

  = [16 x 12mm. ]

  = 192mm.

   &

c. 300mm.

The least of all the 3 conditions is 192mm.

Hence, we can provide c/c spacing of lateral tie as 192mm.

To go through all types of structural design articles, click here.

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Different ways to make your roof top cool./How to reduce the summer heat by making the roof cool?

Let us discuss the different ways to make our rooftop cooler in the summer season.

 1. Terrace garden: 

Growing our own terrace garden helps us in two ways. You will get fresh vegetables for your daily use & also it reduces the terrace top heating. The plants & the soil surface absorb the sunlight & create a cooler atmosphere.

2. Reflective paint:

As the name suggests, these types of paints reflect up to 97% of the sunlight. The coated layer of the paint reduces the heat penetration from the rooftop, which in turn keeps the interior cooler & comfortable.

 

3. Creating shades:

You can create shades over the terrace by using different types of materials. Among them, a green shade net is the cheapest & the best option to block the sunlight. You can build a simple fabrication structure for green shade coverings over the roof. 

4. Heat-reflective flooring:

The heat reflective tiles emit the absorbed solar radiation back into the atmosphere. They are lighter in color to enhance the reflection process. These tiles have a solar reflective index value > 90%, which reduces the inner temperature of the building up to a degree of 20%.

5. Solar panel:

Installation of the solar panel acts as a barrier to the sunlight. The larger the area of the solar panel over the rooftop, the cooler will be the home interior.

6. False ceiling:

The false ceiling blocks the heat penetration by creating a layer of voids in between the roof & the room interior. Among them, the thermocol ceiling is the cheapest & the best option to create a cooler & comfortable interior.

To know it in detail, Go through the article 👇

👀.  What is thermocol ceiling? - advantages & disadvantages.

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Rebar weight calculator./ Weight calculator for reinforcement bars.

 To know the calculation procedure,  Go through the article 👇

👀.   How to calculate the weight of reinforcement bars?

Note: 

This calculation tool has been created with the greatest possible care. However, we cannot be held liable for its correctness.

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Calculator for 4-legged stirrups./ Cutting length calculator for four legged stirrup bar./Calculator for 4-legged lateral ties.

 To know the calculation procedure,  Go through the article 👇

👀.  How to calculate the cutting length of 4-legged stirrups?

The 4-legged stirrup calculator for the MKS  & FPS system is given separately. Calculate according to your requirements.

Note: The cutting length of stirrup-1 & stirrup-2 will be the same in 4-legged stirrups.

Note: 

This calculation tool has been created with the greatest possible care. However, we cannot be held liable for its correctness.

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Calculator for 2-legged stirrups./ Cutting length calculator for two legged stirrup bar./Calculator for 2-legged lateral ties.

 To know the calculation procedure,  Go through the article 👇

👀.  How to calculate the cutting length of 2-legged stirrups?

The 2-legged stirrup calculator for the MKS  & FPS system is given separately. Calculate according to your requirements.

Note: 

This calculation tool has been created with the greatest possible care. However, we cannot be held liable for its correctness.

For more such calculators, click 👇

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How to calculate the cutting length of 2-legged stirrups?/ Calculating the cutting length of 2-legged lateral ties.

 If you are looking for a readymade calculator for 2-legged stirrups, then click here.

 For the calculation procedure, go through the following steps.👇

Let us calculate the cutting length of the 2-legged stirrup as shown below.

Given data :

Column size = 225mm × 300mm.

Clear cover = 40mm.

Rebar diameter = 12mm.

 No. of rebars = 4nos.

Stirrup bar dia. = 8mm.

Calculation:

The cutting length of the stirrup

 =[{(2nos. × (a +b )) + (hook length )} - {(90° bend ) + (135° bend)}]

As you can observe in the above drawing, the stirrup has 

90° bend   👉 3nos.

135° bend 👉 2nos.

 Hook length 👉 2nos.

Therefore, the cutting length of the 2-legged stirrup

 =[{(2nos. × (a +b )) + (2nos.× hook length )} - {(3nos.×90° bend ) + (2nos.×135° bend)}]

Where,

a = [column length - (2nos.× clear cover) - (2 nos. × 1/2 × diameter of stirrup bar.)]

   = [300mm. - (2nos.× 40mm.) - (2nos. × 1/2 × 8mm.)]

   = [300mm. - 80mm. - 8mm.]

  a = 212mm.

b =  [column width - (2nos.× clear cover) - (2 nos. × 1/2 × diameter of stirrup bar.)]

   = [225mm. - (2nos.× 40mm.) - (2nos. × 1/2 × 8mm.)]

   = [225mm. - 80mm. - 8mm.]

 b = 137mm.

 The cutting length of the 2-legged stirrup

 =[{(2nos. × (a +b )) + (2nos.× hook length )} - {(3nos.×90° bend ) + (2nos.×135° bend)}]

 =[{(2nos. × (212mm. +137mm.)) + (2nos.× 10d )} - {(3nos.×2d ) + (2nos.× 3d)}]

 = [{(2nos. × 349mm.) + (2nos.× 10 × 8mm.)} - {(3nos.×2 × 8mm. ) + (2nos.× 3 × 8mm.)}]

= [ {698mm. + 160mm.} - {48mm. + 48mm.}]

= [858mm.- 96mm.]

= 762mm.

= 0.762m.

 For BBS & cutting length of all types of structural members, click here.  

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Calculator for triangular stirrups./ Cutting length calculator for triangular stirrup bar.

 To know the calculation procedure,  Go through the article 👇

👀. How to calculate the cutting length of triangular stirrups?

The triangular stirrup calculator for the MKS  & FPS system is given separately. Calculate according to your requirements.

Note: 

This calculation tool has been created with the greatest possible care. However, we cannot be held liable for its correctness.

For more such calculators, click 👇

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Calculator for diamond stirrups./ Cutting length calculator for diamond stirrup bar.

 To know the calculation procedure,  Go through the article 👇

👀.   Calculating the cutting length of diamond stirrups in column 

The diamond stirrup calculator for the MKS  & FPS system is given separately. Calculate according to your requirements.

Note: 

This calculation tool has been created with the greatest possible care. However, we cannot be held liable for its correctness.

For more such calculators, click 👇

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Calculator for helical stirrups./ Calculator for spiral rings in the pile foundation.

 To know the calculation procedure,  Go through the article 👇

👀. How to calculate the cutting length of spiral stirrups(ring).

Note: 

This calculation tool has been created with the greatest possible care. However, we cannot be held liable for its correctness.

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Calculator for circular stirrups./Cutting length & weight calculator for circular stirrup bars./Calculator for round column lateral ties.

 To know the calculation procedure,  Go through the article 👇

👀.  How to calculate the cutting length of a circular stirrup?

The circular stirrup calculator for the MKS  & FPS system is given separately. Calculate according to your requirements.

Note: 

This calculation tool has been created with the greatest possible care. However, we cannot be held liable for its correctness.

For more such calculators, click 👇

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Calculator for trapezoidal footing./

 To know the calculation procedure,  Go through the article 👇

👀.  Material estimation for M25 grade concrete.

The trapezoidal footing calculator for the MKS  & FPS system is given separately. Calculate according to your requirements.

Note: 

This calculation tool has been created with the greatest possible care. However, we cannot be held liable for its correctness.

For more such calculators, click 👇

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Calculator for columns & beams./ Self weight calculator for columns & beams./ Material calculator for columns & beams.

 To know the calculation procedure,  Go through the article 👇

👀.  Material estimation for M25 grade concrete.

The column & beam calculator for the MKS  & FPS system is given separately. Calculate according to your requirements.

Note: 

This calculation tool has been created with the greatest possible care. However, we cannot be held liable for its correctness.

For more such calculators, click 👇

Instant calculators.

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