Helical reinforcement in columns

 Helical reinforcement 

Helical reinforcement, also known as spiral reinforcement, is a type of reinforcement used in columns and other structural elements of buildings. It consists of helical-shaped bars that are wrapped around the longitudinal steel bars or rebars in a concrete column. The primary purpose of helical reinforcement is to provide additional lateral support and confinement to the concrete, enhancing the column's load-bearing capacity and ductility.

The helical reinforcement helps in controlling cracks and improving the overall performance of the column, especially in earthquake-prone areas. It effectively prevents the concrete from spalling or delaminating during seismic events or other overloading situations.

Overall, helical reinforcement is a valuable technique in structural engineering to ensure the stability and safety of columns in buildings and other structures.

Pitch of helical reinforcement

The pitch of the helical turns should not be more than 

(1) 75mm 

(2) 1/6 dia of core of concrete 

The pitch of helical turns should not be less than 

1- 25 mm 

2- 3 times dia of steel bar forming the helix. 

Diameter 

The diameter of the helix reinforcement shall not be less than one fourth of the diameter of the longitudinal bar, and in no case less than 5 mm.

Cover to reinforcement 

For a longitudinal reinforcing bar in a column, the nominal cover shall not be less than 40 mm, nor less than the diameter of such bar .in the case of columns of minimum dimension of 200 mm or under, whose reinforcing bars does not exceed 12 mm, a cover of 25 mm may be used.

Short and slender compression members 

A compression member may be considered as short when both the selenderness ratio lex/D and ley/b are less than 12.