Understanding Columns in Construction

What is a Column?

A column is a vital part of a building made of reinforced concrete. It’s like a strong pillar that carries a heavy load, causing it to squeeze and become sturdy. Columns are usually much taller than they are wide. When a member is standing up and mainly bears a heavy load, it’s called a column. If it’s tilted or horizontal, it’s called a strut. Columns come in various shapes, like rectangles, squares, circles, and more, depending on how they need to look and what job they have.

Types of Columns

Columns can be divided into different types based on various things:

• Shape: Columns can be square, rectangular, circular, hexagonal, and more.
• Materials: They can be made of wood, bricks, concrete, steel, or a mix of these.
• How They’re Loaded: Some columns get pushed straight down, while others might get pushed a bit sideways.
• Length: They can be short or long.
• Reinforcement: Some have lots of steel bars inside them to make them strong. Others might have fewer.

Reinforcement in Columns

Columns need some extra strength from steel bars. There are two main types of these bars:

• Longitudinal Reinforcement: These bars run lengthwise inside the column. They help the column handle the weight and resist cracking.
• Transverse Reinforcement: These are like rings or stirrups that go around the column. They help hold the longitudinal bars in place and resist bending.

How to Design a Column

Designing a column involves some steps:

• Find out how strong the concrete and the steel can be.
• Calculate how much weight the column has to support. This includes the weight of the column itself.
• Decide how much steel the column will need based on its size.
• Determine the column’s dimensions, like how wide or how tall it should be.
• Check if the column is short or long based on its length and size.
• If it’s short, calculate how much steel it needs and where to place it.
• If it’s long, figure out a reduction factor to make it work like a short column. Then, calculate the steel and dimensions again.

Example – Find the Safe Load for a Column

Let’s say we have a column that’s 4 meters tall and 400 mm wide. It has 8 steel bars, each 20 mm thick. The concrete is grade M20, and the steel is Fe 415.

• First, we find out it’s a short column because its height-to-width ratio is less than 12.
• Then, we calculate the load it can carry, which is around 1093.281 kN.

But if we make the column 8 meters tall, it becomes a long column. To find the safe load now:

• We calculate a reduction factor, which turns out to be 0.8333.
• Then, we apply this factor to the previous load calculation, and the safe load becomes 911.067 kN.

This tells us how strong the column needs to be to support different amounts of weight safely.