KNOW HOW TO CALCULATE THE CUTTING LENGTH OF BENT UP BARS

HOW TO CALCULATE THE CUTTING LENGTH OF BENT UP BARS IN SLAB REINFORCEMENT

As a site engineer, you must know how to calculate the cut length of the bars based on the dimensions of the slab and provide instructions to the bar benders.

In this article we will see how to CALCULATE THE CUTTING LENGTH OF BENT UP BAR Let’s start with an example.

Consider, We have a length of 4.5 m and a slab thickness of 150 mm and a bar diameter of 12 mm and a has the clear cover of 25 mm and a develop length of 45 d.

Where,

Clear span = 4500 mm

Slab thickness = 150 mm

Diameter of bar = 12 mm

Clear cover = 25 mm

Development length = 45d or 50d   (where d is dia of bar)

Calculation

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

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As you can see, there are four bends at 45 ° (a, b, c and d) and two bends which is 90 ° (1, 2)

where,

45° = 1d

90° = 2d

So,

Cutting Length = Clear Span of Slab + (2 X Ld) +(2 x 0.42D) – (1d x 4) – (2d x 2) [BBS Shape Codes]

Where,

d = Diameter of the bar (12mm)

Ld = Development length of bar (50d)

D = Height of the bend bar. (?)

All values are known except ‘d’ in the above formula

D = Slab Thickness – (2 x clear cover) – (diameter of bar)

= 150 – (2 × 25) – 12

D = 88 mm

Now, Substitute all values in the formula

Cutting Length = Clear Span of Slab + (2 x Ld) +(2 x 0.42D) – (1d x 4) – (2d x 2)

= 4500 + (2 x 50 x 12) +(2 x 0.42 x 88) – (1 x 12 x 4) – (2 x 12 x 2)

Ø Cutting Length = 5677.92 mm or 5.677 m.

So for the above-given data, you need to cut the main bars 5.67 m in length.

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