Posts, which are usually made of timber or metal support beams and joists and are used in smaller structures. In contrast, columns carry the loads to the foundation and are common in larger constructions. They are also less flexible in design and more expensive than posts.
What are the Differences Between Post and Column?
While posts and columns are vertical load-bearing members, they differ in their design and purpose.
Here are the differences between a post and a column:
| Features | Post | Column |
|---|---|---|
| Applications | Used for small structures like decks and porches. | Common in large structures like multi-storied buildings, bridges, and industries. |
| Size | Smaller | Larger |
| Materials used | Made from wood or metal | Built from poured or precast concrete, steel, brick, or other composite materials. |
| Ease of construction and installation | Simpler to construct and install | Complex process requiring the use of heavy machinery |
| Flexibility | Flexible | Not flexible |
| Load support | Support in compression | Support in compression and bending |
| Cost | Affordable | Expensive |
| Durability | Less durable | Durable |
What is a Post?
A post is a vertical load-bearing member that supports beams and floor joists.
It is usually made from timber or metal but not concrete.
Generally, posts are used for small structures like decks and porches and provide support in compression.
They can be axially loaded or laterally restrained and must weigh 300 lbs or less.
Moreover, they are easier to install and simpler to construct.
Posts are also cost-effective and easy to modify or replace due to their flexible design.
What is a Column?
A column is a cylindrical-shaped load-bearing structure used to transfer loads from beams and slabs to the foundation.
They are capable of withstanding heavy loads, support larger spans, and are common in large structures like multistoried buildings and bridges.
Additionally, columns provide support in compression and bending.
Unlike posts, columns are made of poured or precast concrete, steel, brick, or other composite materials.
Furthermore, they have a longer lifespan and require less maintenance than wooden posts.
However, the construction and installation are more complex, requiring the use of heavy machinery.
Therefore, they are more expensive than posts.
Moreover, since columns are important load-bearing elements deviating from design parameters affects the structural integrity of the building.
The axial loading applied to columns primarily determines their size.
Other considerations include wind and earthquake loads.
What is the Purpose of a Post Base?
A post base is a support structure installed at the bottom of a post to provide additional stability.
There are many different post bases available, but they all serve the same purpose – to keep the post from tipping over.
The post bases are raised one inch to prevent wood posts from coming into contact with possible water.
With no direct ground contact, it securely fastens the post to any desired horizontal location.
Moreover, post bases ensure excellent corrosion resistance.
5 Types of Columns
Different types of columns are:
| Column Types | Description |
|---|---|
| Material Based Columns | Timber, concrete, metal, brick, block, and stones |
| Reinforcement Based Columns | Includes tied, spiral, and composite columns |
| Shape-Based Columns | Square, rectangular, circular, L-shaped, I-shaped, T-shaped, or channel-shaped. |
| Slenderness Ratio-Based Columns | Long and short columns |
| Load Based Columns | Axially loaded and columns with uniaxial and biaxial eccentric loading |
Material Based Columns
The material used for making a column can vary depending on the requirements.
Each material has its own performance capabilities specified for certain conditions.
The materials that are normally used to make columns include timber, concrete, metal, brick, block, and stones.
Reinforcement Based Columns
Tied Columns
Columns that have square ties around their main vertical reinforcement are known as tied columns.
95% of all columns in a building have tied reinforcement.
Spiral Columns
In spiral columns, the main vertical reinforcement is wrapped by spiral ties as reinforcement, which is continuous and has uniform spacing.
Spiral-tied columns have a greater load-bearing capacity than rectangular-tied columns.
Composite Columns
Composite columns have reinforcements in the form of structural steel sections or pipes instead of longitudinal bars.
These columns have high strength with a relatively smaller cross-section.
Shape-Based Columns
Columns can have many different shapes. The shape of a column influences its various load-bearing capacities.
A column can be squared, rectangular, circular, L-shaped, I-shaped, T-shaped, or channel-shaped.
Slenderness Ratio-Based Columns
Columns are classified as long or short based on their slenderness ratio.
A column is considered to be short if its effective length divided by its smallest lateral dimension is not greater than 12.
If it does exceed 12, then the column is classified as a long column.
While short columns fail primarily due to compression, long columns fail due to buckling or bending.
Load Based Columns
Axially Loaded Columns
Columns that have loads acting at their exact center are termed axially loaded columns.
However, these types of columns are not practical as real-life columns have some degree of eccentricity relative to the applied load.
Columns with Uniaxial Eccentric Loading
The loads on this type of column do not act at the center of the columns but rather at a point on either the x or y-axis of the cross-section.
Columns with Biaxial Eccentric Loading
When the vertical load on the column does not act at its center and is also not on the rectangular axes, but lies somewhere in between the two rectangular axes, then the column is said to be biaxially loaded.
The load, in this case, lies between the x and y planes.
Frequently Asked Questions(FAQ)
How Much Do Columns Weigh?
An 8-foot column has an approximate weight of about 18 pounds.
This makes it easy to move them and increases their versatility.
What is the Minimum Size for a Column?
The minimum recommended size of a column cross-section is about 9” x 12”.
A column of this size has a great load-bearing capacity and performs very well.
What is the Difference Between Piers and Columns?
Columns are uniform in size, whereas piers are wider at the base and narrower at the top.
Additionally, the load-bearing capacity of piers is higher than columns.
