While Posts and Columns are both vertical load-bearing members, a column is the main vertical support used in concrete construction, while a post is made of timber. A post may be erected from wood or metal, but not from concrete.
Posts are also often mistaken for studs which are lighter vertical members.
The frame of a building can be made using a number of different materials and have multiple horizontal and vertical load-bearing structures.
In construction processes that use concrete as the main construction material, the frames comprise of beams and columns that can resist heavy loads.
Contrarily, timber construction uses timber components to make up its frame.
These components include beams and posts with a lesser load-carrying capacity than concrete beams and columns.
What is a Post?
A post is a vertical load-bearing member. It is usually made from timber or metal but not concrete.
Posts can be axially loaded or laterally restrained and must weigh 300 lbs or less.
The words pillar, columns, and posts are often used interchangeably.
What is a Column?
A column is a vertical load-bearing structure used to transfer loads from beams and slabs to the foundation.
Columns are incorporated in all major projects including bridges, houses, buildings, etc.
The size of columns is determined based primarily on the axial loading applied to them.
Other considerations include wind and earthquake loads.
Columns can be categorized into different types based on various factors.
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.
This is especially important for wooden post tops and posts exposed to water.
With no direct ground contact, it securely fastens the post to any desired horizontal location.
Post bases ensure outstanding corrosion resistance.
5 Types of Columns
Columns can be classified into different categories based on reinforcement type, shape, material, applied load, and slenderness ratio.
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
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.
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 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.
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 and channel-shaped, etc.
Slenderness Ratio-Based Columns
Columns are classified as either long or short based on the value of 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.
Short columns fail purely due to compression. They get crushed under excessive compressive loads.
Long columns fail by undergoing 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.
The terms "column" and "post" are not significantly different from one another.
Both are a way of referring to vertical load-bearing structures in a structural frame.
A post is often used in European countries.
Since most of the construction that takes place there is made from timber, posts are associated with timber as well.
Columns on the other hand are vertical load-bearing members made mostly from concrete.
Posts are thus vertical load-resistant structures made of either timber or metal, whereas columns can be made from concrete, timber, and metal.
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.
Such columns are used at entrances.
What Amount of Weight can a Column Bear?
The weight that a column can support depends on many factors.
This includes the shape of the columns and the size of their cross-section.
Moreover, column reinforcement, effective length, and the type of concrete from which it has been cast also play a significant role in a column's load-bearing capacity.
What is the Minimum Cross-section Dimension for a Column?
The minimum recommended size of column cross-section is about 9”x12” or 225mmx300mm.
A column of this size has a great load-bearing capacity and performs very well.
The minimum grade of concrete recommended for casting columns is M20 according to the IS standards.