Understanding the Factored Load

The factored load considers additional safety by increasing the actual load. This ensures stability and prevents failure.
Let’s assume:

• Dead Load = 1200 kN
• Live Load = 600 kN

Now, increase the total load by 50% for safety:

Pu = 1200 + 600 = 1800 kN

Alternatively, as per IS 456: Table 18,

This value will be used in further calculations.

Essential Design Parameters

According to IS 456 guidelines, the following parameters apply:

• Concrete Grade (fck) = M30
• Steel Grade (fy) = Fe 500
• Factored Load (Pu) = 1800 kN

Use the IS 456 equation for axial load-bearing columns:

Pu = 0.4fckAc + 0.67fyAsc

Where:

• Ac = Area of concrete
• Asc = Area of steel
• Ag = Gross area of column section

Assume:

• Asc = 1% of Ag
• Ac = 99% of Ag

This gives:
Asc = 0.01Ag,
Ac = 0.99Ag

Column Area Calculation

Now, apply the values to the equation:

1800 × 10³ = 0.4 × 30 × 0.99Ag + 0.67 × 500 × 0.01Ag

Simplify the equation:

1800000 = 11.88Ag + 3.35Ag
1800000 = 15.23Ag

Solve for Ag:

Ag = 1800000 / 15.23
Ag ≈ 118187.78 mm²

Now take the square root to find side length (assuming a square column):

√118187.78 ≈ 343.78 mm

For practicality and simplicity, round it:

Adopted Column Size = 350 mm × 350 mm

Final Recommended Column Size

Based on the above calculation:

• Column Dimensions = 350 mm × 350 mm
• This size ensures the column safely supports the applied load.
• The design adheres to IS 456 provisions for safety and performance.

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