In this post, I’ll show a step-by-step process of column reinforcement calculation.
After learning the process, you’ll be able to calculate reinforcements of columns for any type of building structure.
So, let’s discuss…
The Step By Step Process Of Column Reinforcement Calculation
You’ll have a structural drawing book in your construction project. Keep that with you.
Step-1: Sum Up The Number Of Similar Columns
First, open the column layout plan from the structural drawing book.
That’ll look something like:
Next, count the number of similar columns.
In our example drawing,
- C1 – 2 nos
- C2 – 3 nos
- C3 – 1 no
- C4 – 2 nos
- C5 – 2 nos, and
- C6 – 1 no
Step-2: Get The Column Reinforcement Schedule
A Column Reinforcement Schedule is a drawing sheet that you’ll find in the structural drawing book.
The name of the drawing sheet may differ in your drawing book. It’s sometimes called COLUMN SCHEDULE, or COLUMN REINFORCEMENT DETAILS.
That looks something like:
With the drawing, …
Step-3: Calculate The Longitudinal Column Reinforcement
Longitudinal bars are also called vertical bars.
First, Count The Number Of Vertical Bars In A Column
Let’s take the C1 from our example drawing.
The column has 6 numbers of 16mmØ bar.
Next, Get The Length Of A Vertical Bar
To get the length of a verticle bar you need to know where you’re going to place the column reinforcement.
Let’s say you’re going to place a column reinforcement from the footing.
In that case, the vertical section of the column will look something like:
Now you can easily calculate the length of a vertical bar.
In the above image,
The length of a vertical bar is,
= Thickness of the footing + Height of the neck column + Grade beam height + Floor height + bend length – concrete cover in footing – concrete cover in the roof slab
From the drawing above:
- The thickness of the footing = 1 foot
- Height of the neck column = 4 feet
- Grade beam height = 1 foot
- Floor height = 10 feet
- Bend length = 1½ foot
- Concrete cover in footing = 3 inches (concrete cover is normally kept 3” below grade)
- Concrete cover in roof slab = 1 inch (It varies. Read general notes in your structural drawing book.).
So the length is,
= 1 + 4 + 1 +10 + 1½ – 0.25 – 0.08 (3″ = 0.25′, 1″ = 0.08′)
= 17.17 feet.
Note: Sometimes we need to provide laps in vertical bars. Consider adding the lap length while calculating the length of a vertical bar. The length of a lap varies depending on the size of the bars. There must be some notes about the lap length in your structural drawing.
Next, Calculate The Total Length Of Longitudinal Bars
As we have 6 numbers of 16mmØ bar in the column (C1),
So the total length is,
= 6 × 17.17
= 103.02 feet.
Finally, Calculate The Weight Of Vertical Bars
As we know,
The weight of bars = length of bars × unit weight of the bar
= 103.02 × 0.48 [unit weight of 16mmØ is 0.48 kg/feet, read this post to know more about this]
= 49.45 kilograms.
Step-4: Calculate Stirrups Of Columns
You’ll need two things to calculate reinforcement of stirrups-
- The spacing of stirrups and
- The size of the stirrup’s bar
You’ll get these data in the Column Schedule drawing sheet.
Let’s calculate stirrups for the column (C1) in our example.
First, Calculate The Required Number Of Stirrups
The formula is,
Number of stirrups = (Length of the column ÷ Spacing of stirrups) + 1
Here, the length of the column (C1) is,
= Height of footing + Neck column height + Grade beam height + Floor height
= 1 + 4 + 1 + 10
= 16 feet
And the spacing of stirrups is 6″ c/c.
So, the number of stirrups = (16′ ÷ 6″) + 1
= 33 nos.
Next, Calculate The Length Of A Stirrup bar
The formula is,
= (2 × long sides of the stirrup) + (2 × short sides of the stirrup) + (2 × hook length)
The long side of the stirrup is,
= The long side of the column – 2 × concrete cover
= 20″ – 2 × 1½″
The short side of the stirrup is,
= The short side of the column – 2 × concrete cover
= 12″ – 2 × 1½″
And, the hook length of the stirrup is 3″.
So, the length of a stirrup is,
= (2 × 17″) + (2 × 9″) + (2 × 3″)
Or, 4.83 feet.
Now, Calculate The Total Length Of Stirrups
The formula is,
= Number of stirrups × Length of a stirrup bar
= 33 × 4.83′
= 159.39 feet.
Finally, Calculate The Weight Of Stirrup Bars
The weight of bars is,
= Length of stirrups bars × unit weight of the bar
= 159.39 × 0.19
= 30.28 kilograms.
Step-5: Calculate Total Column Reinforcement For C1
So far, we’ve calculated the reinforcement for one column (C1).
And the required reinforcement is,
- 16mmØ bars = 49.45 kilograms
- 10mmØ bars = 30.28 kilograms
But we have 2 numbers of C1 columns in our example project.
So the total required reinforcement of C1 columns for our project is,
- 16mmØ bars = 49.45 × 2 = 98.90 kilograms
- 10mmØ bars = 30.28 × 2 = 60.56 kilograms
This is the process of column reinforcement calculation.
Follow the process (step-3 to step-5) to calculate reinforcement for the remaining columns (C2 to C6).
The process of column reinforcement calculation is actually easy.
You first need to summarize the different types of columns.
Then calculate the longitudinal and stirrup bars of a column.
After that, multiply the weight of reinforcement with the number of columns.
Now Your Turn:
How do you calculate column reinforcement in your project?
Do you know any other easy process other than the process I’ve discussed in this post?
Please share in the comments below…