# How to Find Cutting Length of Bent Up Bars in Slab

## Why Crank Bars are Provided in Slab

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Diameter of the bar = 12mm
Clear Cover = 25mm
Clear Span (L) = 8000mm
Slab Thickness = 200 mm
Development Length (Ld) = 40d
Solution:
Cutting Length = Clear Span of Slab + (2 x Development Length) + (2 x inclined length) – (45° bend x 4) – (90° bend x 2)
Inclined length = D/(sin 45°) – dD/ (tan 45°) = (D/0.7071) – (D/1)= (1D – 0.7071D)/0.7071= 0.42 D
As you can see there are four 45°bends at the inner side (1, 2, 3 & 4) and two 90° bends (a, b).
45° = 1d ; 90° = 2d
Cutting Length = Clear Span of Slab + (2 x Ld) + (2 x 0.42D) – (1d x 4) – (2d x 2)
Where,
d = Diameter of the bar.
Ld = Development length of bar.
D = Height of the bend bar.
In the above formula, all values are known except ‘D’.
So we need to find out the value of “D”.
D = Slab Thickness – (2 x clear cover) – (diameter of bar)
= 200 – (2 × 25) – 12
= 138mm
Now, putting all values in the formula
Cutting Length = Clear Span of Slab + (2 x Ld) +(2 x 0.42D) – (1d x 4) – (2d x 2)
= 8000 + (2 x 40 x 12) + (2 x 0.42 x 138) – (1 x 12 x 4) – (2 x 12 x 2)
Cutting Length = 8980 mm or 8.98 m.
Result:
Cut the main bars 8.98 m in length.

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