Updated August 27th, 2017
As horizontal bar we use stirrups and ties in column. Stirrup also has some other name in construction sector. Such as ring, shear reinforcement, etc.
For making stirrup for column you have to calculate the cutting length of bar for stirrup, you have to calculate the number of stirrups and you have to determine the size of stirrup.
You can do this in 4 easy steps.
4 Easy Steps for Making Column Stirrup
Making column’s stirrup involves following 4 steps of work.
- Determine the size of stirrup
- Calculating cutting bar length for stirrup
- 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″ x 40″. We know the concrete clear cover for reinforcement of column is 1½”.
So the length of stirrup will be 40″-2×1½”=37″ and width will be 20″-2×1½”=17″.
So the size of the stirrup is 37″x17″.
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 – 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′.
Let’s discuss a little about hook length.
Hook length is calculated by a formula that is 6db (diameter of bar).
So the hook length for 10mmø bar is,
6 x 10 = 60 mm.
But length of 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 9.5′. 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 90° bend and two 135° hook.
For each bend, the length of bar will be reduced. There is a certain formula to calculate the reduced length for bend.
The formula needs various calculation process. I’ll write about the formula some other day in this blog. So subscribe via Email to get it in your inbox when it happens.
Below I’m giving a chart for reduced length for a 90° bend for different diameter of bar.
10 mmø bar – 1″
12 mmø bar – 1¼”
16 mmø bar – 1½”
Since, we are using 10 mmø bar for our stirrup so the cutting bar length will be,
9.5′ – 3 x 1″ (bend deduction is ignored for 135° bend).
So, you have to cut 9′-2″ length of 10mmø bar.
That means, cutting bar length for the stirrup is 9′-2″.
3. Calculating the Number of Stirrups
See 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 top ¼th portion of clear column’s length. S2 is provided in the middle half portion of clear column’s length.
Clear column’s length means the height of column between the top of floor to bottom of beam.
You also should provide 2 numbers of stirrup for column into beam-column joint.
Now let’s calculate the numbers of stirrups for column.
The floor height is 10′.
Beam height is 2′
Clear height of column is,
= floor height – beam height
= 10′ – 2′
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 large project where vast quantity of stirrups are required.
But, we often make stirrups by hand 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 stirrup. Also don’t forget to make the hook angle at 135°.
Symbol used in this post
“ – inch
‘ – foot
° – degree
db – diameter of 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 bend of different dia bar?