Updated August 20th, 2019
An RCC column has two types of bar. One is the longitudinal bar and another is the horizontal bar.
As the horizontal bar, we use stirrups and ties. Stirrup also has some other names in the construction sector. Such as Ring, Shear reinforcement, etc.
For making column stirrups, you have to calculate the cutting length of a bar and the number of required stirrups and then determine the size of the stirrup.
You can do this in four easy steps.
4 Easy Steps for Making Column Stirrups
Making column’s stirrup involves the following 4 steps of work.
- Determining the size of stirrups
- Calculating the cutting length of a bar
- Calculating the number of stirrups
- Bending the bar in stirrup’s shape
1. Determine The Size of Stirrup
See the above image. The column size is 20″ × 40″ and the concrete clear cover for reinforcement is 1½”.
So the length of stirrup will be,
= Long side of column – 2 × clear cover
=40″-2 × 1½”
And the width will be,
= The short side of the column – 2 × clear cover
=20″-2 × 1½”
So the size of a stirrup is 37″ × 17″.
2. Calculating Cutting-Bar-Length for Stirrup
Before cutting the bar you have to calculate the cutting bar length for the stirrup.
There are two terms – the Actual bar length and the Cutting bar length.
The actual bar length of a stirrup is,
=2 × length + 2 × width + 2 × hook’s length
= 2 × 37″ + 2 × 17″ + 2 × 3″
= 114″ or 9½ feet.
Let’s discuss a little about hook’s length.
The hook length is calculated by a formula that is 6db (db=diameter of the stirrup bar).
So the hook length for 10mmø bar is,
= 6 × 10
= 60 mm.
But the length of a hook should not be less than 75mm (as per code).
So the hook length for the stirrup is 3″ (75mm = 3″).
The actual bar length of the stirrup is 9½ feet.
But the cutting bar length will be less than the actual bar length.
See the above image. That is our stirrup.
The stirrup has three numbers of 90° bend and two numbers of 135° hook.
For each bend, the length of the bar will be reduced.
There is a certain formula to calculate the reduced length for a bend.
The formula needs various calculation process. I’ll write about the formula some other day in this blog.
Below I’m giving a chart for the reduced length of a 90° bend for different size of bars.
- 10 mmø bar – 1″
- 12 mmø bar – 1¼”
- 16 mmø bar – 1½”
Since, we are using 10 mmø bar for our stirrups so the cutting bar length will be,
=9½’ – (3 × 1″) (bend deduction is ignored for 135° bend).
So, you have to cut 9′-3″ length of 10mmø bar.
That means, cutting bar length for the stirrup is 9′-3″.
3. Calculating The Number of Stirrups
In the image above, there are two types of spacing for stirrups. One is S1 and another is S2. S1 is spaced 4″ c/c and S2 is spaced 8″ c/c.
S1 is provided in the bottom ¼th portion and the top ¼th portion of clear column’s height.
S2 is provided in the middle half portion of the clear column’s height.
The clear column’s height means the height of a column between the top of the floor to the bottom of the roof-beam.
You also should provide 2 numbers of stirrups into beam-column joint.
Now let’s calculate the numbers of required stirrups for the column.
The floor height is 10 feet.
The roof-beam height is 2 feet.
So the Clear height of the column is,
= floor height – beam height
= 10′ – 2′
The required number of stirrups are,
= (4’÷4″) + (4’÷8″) + 2 + 1 (1 bar should be added for getting the correct number of stirrups).
= 21 nos.
4. Bending The Bar in Stirrup’s Shape
You can use stirrup-making-machine for a large project where a vast quantity of stirrups is required.
But, we often make stirrups manually in our project.
For making stirrups by hand you need a stand and a handle.
See the above image. That is a hand-made stand and a handle. You can make stirrup with these tools.
Just place the rod in the stand and bend the rod with the handle. You have to go for trial and error method to get the desired size of a stirrup. Also, don’t forget to make the hook angle at 135°.
Symbols used in this post:
- “ – inch
- ‘ – foot
- ° – degree
- db – diameter of the bar
- nos – numbers
- ø – diameter
- c/c – center to center distance
How do you make stirrup bending stand? How do you make the handle? How do you calculate the deduction length for the bend of different size bars? Please share in the comments below…
Editor’s Note: This post was originally published in May 2017 and has been completely revamped and updated for accuracy and comprehensiveness.