The steps involved in producing stirrup in column

There are two types of bars in a RCC column i.e. longitudinal bar and horizontal bar.

In horizontal bar, the stirrups and ties are utilized in column. Stirrup is also known as ring, shear reinforcement, etc.

To form stirrup for column, it is necessary to work out the cutting length of bar for stirrup as well as calculate the number of stirrups and the size of stirrup.

It can be performed in following 4 easy steps.

1. Find out the size of stirrup
2. Compute the cutting bar length for stirrup
3. Compute the number of stirrups
4. Bending the bar in stirrup’s shape

1. Find out the Size of Stirrup
Suppose, the column size is 20″ x 40″. The concrete clear cover for reinforcement of column is taken as 1½”.

The length of stirrup should be 40″-2×1½”=37″ and width 20″-2×1½”=17″.

Therefore, the size of the stirrup is 37″x17″.
Work out Cutting-Bar-Length for Stirrup

Prior to cut the bar, work out the cutting bar length for the stirrup.
There exist actual bar length and cutting bar length.

The actual bar length of stirrup is calculated as follow :-
2 x length + 2 x width + 2 x hook’s length
= 2 x 37″ + 2 x 17″ + 2 x 3″
= 114″or 9.5′.

Hook length is computed with the formula like 6db (diameter of bar).
Therefore, the hook length for 10mmø bar is provided as follow :-
6 x 10 = 60 mm.
But, the length of hook should not be under 75mm (as per code).
Therefore, the hook length for the stirrup is 3″ (75mm = 3″).

The actual bar length of the stirrup is 9.5′. But, the cutting bar length should be under the actual bar length.

Assume, the stirrup contains three 90° bend and two 135° hook.
For every bend, the length of bar will be decreased.
Given below, a chart for reduced length for a 90° bend for various diameters of bars.
10 mmø bar – 1″
12 mmø bar – 1¼”
16 mmø bar – 1½”

As 10 mmø bar is applied here for the stirrup, so the cutting bar length should be,
9.5′ – 3 x 1″ (bend deduction is not taken for 135° bend).
= 9′-2″
Therefore, it is required to cut 9′-2″ length of 10mmø bar.
It signifies, cutting bar length for the stirrup is 9′-2″.

Compute the Number of Stirrups
Assume, there exist two types of spacing for stirrups. One is taken as S1 and another is S2. S1 is placed 4″ c/c and S2 is placed 8″ c/c.
S1 is arranged in the bottom ¼th section and top ¼th section of clear column’s length. S2 is arranged in the middle half portion of clear column’s length.
Clear column’s length stands for the height of column among the top of floor to bottom of beam.
There should be 2 numbers of stirrup for column into beam-column joint.
The numbers of stirrups for column will be computed as follow :-
The floor height is 10′.
Beam height is 2′
Clear height of column is,
= floor height – beam height
= 10′– 2′
=8′
Number of stirrups should be,
= 4’/4″ + 4’/8″ + 2 + 1 (1 bar is included for obtaining the exact number of stirrups.)
4. Bending the Bar in Stirrup’s Shape
To deal with vast quantity of stirrups in a large project, the stirrup making machine can be used.
But, the stirrups can be formed manually with a stand and a handle.
Just set the rod in the stand and curve the rod with the handle. Go through trial and error method to obtain the desired size of stirrup. Create the hook angle at 135°.