How to create stirrup for column with some easy to follow steps

A RCC column contains two types of bars i.e. longitudinal bar and horizontal bar. The stirrups are used in horizontal bar and the ties are used in column. Stirrup is also known as ring, shear reinforcement, etc.

To produce stirrup for column, it is required to measure the cutting length of bar for stirrup as well as compute the number of stirrups and find out the size of stirrup.

It can be performed in following 4 easy steps.

1. Ascertain 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

Ascertain the Size of Stirrup
Suppose, the column size is 20″x 40″and the concrete clear cover for reinforcement of column is 1½”.
Therefore, the length of stirrup should be 40″-2×1½”=37″and width should be 20″-2×1½”=17″.
Therefore, the size of the stirrup is 37″x17″.

2. Compute Cutting-Bar-Length for Stirrup
Prior to cutting the bar, it is necessary to work out the cutting bar length for the stirrup.
There exist two terms like actual bar length and cutting bar length.
The actual bar length of stirrup is, 2 x length + 2 x width + 2 x hook’s length
= 2 x 37″ + 2 x 17″ + 2 x 3″
= 114″ or 9.5′.

To compute hook length, a formula that is 6db (diameter of bar) is used.
Therefore, the hook length for 10mmø bar is, 6 x 10 = 60 mm.

But length of hook should not be under 75mm (as per code).
So 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.

3. Work out the Number of Stirrups
Suppose, there are two types of spacing for stirrups. One is S1 and another is S2. S1 is spanned 4″c/c and S2 is spanned 8″c/c.
S1 is arranged in the bottom ¼th portion and top ¼th portion of clear column’s length. S2 is arranged in the middle half portion of clear column’s length.

Clear column’s length signifies the height of column among the top of floor to bottom of beam.
One can also give 2 numbers of stirrup for column into beam-column joint.
The numbers of stirrups for column are calculated 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 are,
= 4’/4″ + 4’/8″ + 2 + 1 (1 bar should be included for obtaining the exact number of stirrups.)
= 21 nos.

4. Bending the Bar in Stirrup’s Shape
Stirrup-making-machine is suitable for large project where huge quantities of stirrups are necessary.
It is also possible to produce stirrups manually and for this purpose a stand and a handle are required.
Just set the rod in the stand and twist the rod with the handle. Employ trial and error method to obtain the required size of stirrup. Always remember to maintain the hook angle at 135°.

Source: www.acivilengineer.com