**If you are looking for a readymade calculator for helical stirrups, then** **click here.**

** For the calculation procedure, go through the following steps.ðŸ‘‡**

The front view and cut section-AA of the pile are shown below so that you will clearly understand the calculation procedure of the spiral stirrup.

The cutting length of the spiral stirrup is given by the formula

=n√C2 + P2

Here, n = number of turns of the helical stirrup ( no. of the pitch in total pile length ).

C = circumference of the helical stirrup.

P = pitch of the helical stirrup.

Now, let us redraw the above diagram with mathematical values for the calculation purpose.

__Given data:__

Length of pile = 18m.

Diameter of pile = 750mm = 0.75m

Clear cover = 50mm =0.05m

Pitch = 150 mm. = 0.15m

The diameter of helical stirrup bar = 8mm.= 0.008m.

__1. Number of turns ( n ):__

n = [( length of pile ÷ pitch ) + no. of closure rings]

= [ (18m ÷ 0.15m ) + 2 ]

= 120 + 2

=** 122 nos.**

**Note**: Here, no 2 i.e. added denotes the closure rings at the top & bottom of the helical stirrup as shown in the 1st drawing.

__2. Circumference of the helical stirrup ( C ):__

C = Ï€D or 2Ï€r

Here,

r = [(diameter of pile ) - ( 2 nos. × clear cover ) - (2 × 1/2 × diameter of the spiral stirrup bar )] ÷ 2

r = [(750mm ) - ( 2nos. × 50mm ) - (2 × 1/2 × 8mm )] ÷ 2

= [750mm - 100mm -8mm] ÷ 2

= [642mm] ÷ 2

= 321mm.

r = **0.321m.**

Circumference of the helical stirrup

C = 2Ï€r

= [2 × 3.142 × 0.321 m.]

C = **2.017 m.**

**The cutting length of the helical stirrup or spiral stirrup **

= n√C2 + P2

= 122 × √2.0172 + 0.152

= 122 × √ 4.068 + 0.0225

= 122 × √ 4.091

= 122 × 2.023

= **246.76m**

To get the exact cutting length of the spiral stirrup bars, we have to add lap length, as the length of an individual bar is limited to **12m**.

Let us provide a lap length of **50d**, where d = diameter of the helical bar.

__Number of lapping required__

= [Calculated length of the helical bar ÷ length of a single bar.]

= [246.76m ÷ 12m]

= 20.56 say **21nos.**

**Go through the article****ðŸ‘‡**

**ðŸ‘€. Calculating the volume of concrete in a triangular pile cap having 3-piles**

__Total length of the helical stirrup bar required in a pile__

= [ calculated cutting length of the bar + ( no. of lapping × lap length )]

= [246.76m. + ( 21 nos. × 50d )]

= [246.76m. + ( 21 × 50 × 0.008m. ) ]

= [246.76m. + 8.4m.]

= **255.16m.**

**Go through the article****ðŸ‘‡**

**For BBS & cutting length of all types of structural members, click here.**

**If you have any quarries, you can ask me in the comment boxðŸ‘‡.**

**Thank you for going through this calculation procedure❤. Have a good dayðŸ˜„**

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