Different types of stirrups are used in reinforcement according to the loads and stress induced on the structural members.
The only formula that we need to remember is,
Cutting Length of Stirrups = Perimeter of stirrup + Hook Length – Elongated Bend Length
Why subtracting the bend? – Because when we bend the steel bar, the bar’s length will slightly increase due to the stretch (elongation). The length depends on the angle of the elongation. That’s the reason we subtract it.
Let’s calculate the cutting length of the above rectangular stirrup
Cutting Length of Stirrup = Perimeter of Stirrup + 2 x Hook Length – 3 x 90° bends – 2 x 135° bends
= 2 (520+220) + (2 x 9d) – (3 x 2d) – (2x3d)
= 2(1480) + (2x9x8) – (3x2x8) – (2x3x8) = 3008 mm
Let’s calculate the cutting length of the above square stirrup
Cutting Length of Stirrup = Perimeter of Stirrup + 2 x Hook Length – 3 x 90° bends – 2 x 135° bends
= 4a + (2 x 9d) – (3 x 2d) – (2x3d)
= (4×200) + (2x9x8) – (3x2x8) – (2x3x8) = 848 mm
Let’s calculate the cutting length of the above circular stirrup
Cutting Length of Stirrup = Perimeter of Stirrup + 2 x Hook Length – 2 x 135° bends
= 2πr + (2 x 9d) -(2x3d)
= (2×3.14×300) + (2x9x8) – (2x3x8) = 1980 mm
Let’s calculate the cutting length of the above triangular stirrup
Cutting Length of Stirrup = Perimeter of Stirrup + 2 x Hook Length – 4 x 135° bends
To find out the perimeter of the triangle stirrup, we need to calculate the Value of H
As from the diagram (pythagorean theorem), H = √(a2)+((b/2)2)
H = √(3502)+(1252) = 372 mm
Cutting Length of Stirrup = Perimeter of Stirrup + 2 x Hook Length – 4 x 135° bends
(Perimeter of stirrup = a + H + H = 250+372+372 = 994 mm
= 994 + (2 x 9d) – (4x3d) = (994) + (2x9x8) – (4x3x8) = 1042 mm
Cutting Length of Diamond Stirrup = Perimeter of Stirrup + 2 x Hook Length – 3 x 90° bends – 2 x 135° bends
= (4 x y) + (2 x 9d) – (3x2d) – (2x3d) = (4*y) + 18d-6d-6d = 4y + 6d
In order to get perimeter of the diamond stirrup, we have find out the value of y (ref the diagram)
a = 400 – (2×25) = 350 mm
b = 450 – (2×25) = 400 mm
(pythagorean theorem), y2 = (a/2)2 + (b/2)2 = (350/2)2 + (400/2)2
Y = 266 mm
Therefore, cutting length of Diamond Stirrup = (4×266) + (6 x8) = 1112 mm
Happy Learning 🙂
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is this dia of bar for bending portion acoording to ACI or ICI