Direction: Assume straight line instead of parabola for stress-strain curve of concrete as follows and partial factor for safety as 1.0.
A rectangular under-reinforced concrete section of 300 mm width and 500 mm effective depth is reinforced with 3 bars of grade Fe G15, wach of 16 mm diameter. Concrete mix is M20.
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The depth of the neutral axis obtained as per IS: 456-2000 differs from the depth of neutral axis obtained in 26 (a) by
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- 15 mm
- 20 mm
- 25 mm
- 32 mm
Correct Option: C
Tension force = compression force
0.87 fy Ast = 0.30 fck = b.xu
0.87 × 415 × 3 × (π/4) × 162
= 0.36 × 20 × 300 × xu
∴ xu = 100.3 mm
Difference = 100.3 – 76 ≈ 25 mm
