# Cutting length of spiral ring ?

The spiral ring is used in the binding of pile inner bar that is used is called master rings which are similar to circular stirrups, but we are not provided a hook in this ring, but outside we have a spiral ring to bind the pile which is called spiral bars. The cutting length of the spiral ring is very simple and easy.

Let’s solve this example.

**Example:**

We have a length of the pile which is 20m and pitch or spacing for the spiral bar is 200mm and dia of the pile is 1m and dia of the spiral bar is 8mm, assume clear cover is 50mm in this case?

**Given data :**

Dia of pile = 1000mm or 1m

Pitch or spacing of spiral bar = 200mm

Length of pile = 20m

Dia of spiral bar = 8mm

Clear cover = 50mm

**Solution:**

1st we find the radius of the spiral and then length of the spiral ring which completes the one pitch which distance is given in the data,

2nd find out the no of spirals and then the how many no of laps are required in the total length of the spirals.

**1: Radius of spiral ring**

= Radius of pile (d2) – clear cover – half of spiral dia bar

= 500 – 50 – 4

= **446 mm**

So lenght of 1 no of spiral ring is

= 2 x 3.14 x r

= 2 x 3.14 x 446

= **2800 mm or 2.8m Ans..**

**2: No of spiral **

no of spirals

= lenght / spacing of pitch + 1

= 20000 / 200 + 1

= 100 + 1

= **101 nos**

101 nos of pitches are completed for spiral bar in this lenght of given pile.

So total length of the spiral bar is

total length

= no of pitches x radius of the pile

= 101 x 2.8m

= **282.8m**

** **

**Laps **

We know that length of one full bar is 12m so lapping are required in this case.

no of laps = total lenght of spirals – 1 / lenght of one bar

= 282.8 – 1 / 12

= 23.56 – 1

= **22.56 say 23 nos**

23 nos 0f laps are required

Lap considered = 50d

< where d is dia of bar>

= 50 x 8

= 400mm or 0.4m

**Total lenght of spiral bar**

Total lenght of laps

= 23 x 0.4

= **9.2m**

Total lenght of spiral rings

= 282.8 + 9.2

= **292m**

**Weight:**

= d^{2}/162 x lenght

= 8 x 8 / 162 x 292m

= **115.35 kg Answer…**