How to work out the cutting length of a spiral or helix bar

This is another informative tutorial for civil engineering students presented by the renowned engineer S.L. Khan.

The video provides useful guidance to find out the cutting length concerning a spiral or helix bar.

The spiral bars are utilized in pile foundations to give greater lateral support. It has superior resistance strength against lateral forces or buckling as compared to the non continuous circular ring or ties. It is also defined as helical reinforcement.

The functionality of spiral bars or helical bars is superior as compared to circular Tie bars or stirrups regarding circular columns.

The spiral that is arranged around the bars of the column operates to give support in the transverse direction and stops the column from barreling.

The spiral bars are also used in piers and round column.

Here, the calculation is done on the basis of the following data:-

Height of the spiral bar is taken as 15 feet.

Diameter of the top portion and bottom portion of spiral bar is taken as 4 feet.

Spacing among two spiral i.e. pitch is taken as 3 feet.

The length of the helix/spiral bar is unknown.

The length can be calculated with the following formula:-

n√C2 + p2

Here, n denotes number of turns.

C denotes circumference of spiral.

P denotes pitch

The number of turns (n) is calculated as follow:-

n = H/p = 15/3 = 5

The calculation for circumference is made as follow:-

Circumference = πD

C = π(4)

C = 12.566 feet

By putting the above value, the length of helix can be determined.

Length of the helix = 5 x √12.5562 + 32 = 64.59 or 65 feet

To get more clear ideas, go through the following video tutorial.

Video Courtesy : Engineer Boy

Spiral or Helix Bar