Column and Strut: Definition, Types and Their Differences

Hello, friends today we are going to discuss the column and strut in which you will learn what is column and strut, types and at the last also we will know what is the difference between column and strut.

So without wasting time let's get started.

What is a Column?

A vertical structural member or a vertical component of a machine or structure, on which axial compressive load is applied, is called a column.

Columns are subjected to vertical compressive loads only.  

Example - Pillars of buildings, pillars of road bridges, pillars of rail bridges, etc.

What is Strut?

Such a component of a machine or structure that is mounted in a position other than vertical and on which axial compression force acts is called a strut.

A strut is comparatively shorter than a column & it may be horizontal, vertical, or inclined. 

Struts are subjected to horizontal, vertical, or inclined loads. 

For example, struts are used in trusses, frames, etc. 

All columns are struts but all struts are not columns.

Now we will know the classification of columns but before knowing the classification of columns we have to first know the slenderness ratio and radius of gyration because columns are classified on the basis of slenderness ratio and radius of gyration.

Slenderness Ratio 

The slenderness ratio is defined as the ratio between the length of the column and the minimum radius of gyration with respect to the same bending axis. 

It is denoted by S.

The slenderness ratio is equal to the ratio of the effective length L of a column and the minimum radius of gyration K at the center of gravity of its cross-section.

Slenderness Ratio = (Length of Column / Minimum Radius of Gyration)

S = L/K

Radius of Gyration 

The radius of gyration is defined as that distance from a given axis up to a point where the entire area is assumed to be concentrated.
It is denoted by k.

 K=   ✓(I/A)

Types of Columns

There are following types of columns are used on the basis of slenderness ratio.

Short Columns

Columns that have a slenderness ratio of less than 32 or their lengths less than 8 times their respective diameters are called short columns. 

In short columns, buckling stresses are negligible as compared to direct compressive stresses.

 Long Columns

Columns that have a slenderness ratio of more than 120 are called long columns. 

In these columns, direct compressive stresses are very small as compared to buckling stresses, thus they can be neglected. 

Medium Size Columns

Columns that have a slenderness ratio between 32 and 120 or their lengths 8 to 30 times their respective diameters are called medium size columns or intermediate columns. 

In these columns, both the buckling as well as direct compressive stresses are of significant value.

column and strut
Column Vs Strut

Difference Between Column and Strut

There are the following differences between column and strut.

Column Strut
Columns are vertical members subjected to axial compressive loads only. It is designed in such a way to take a gravitational load, shear force, buckling force, bending moment, eccentric moment and transfer all these loads from the roof to the floor of the building or structure. Struts are inclined members that are also subjected to axial compression loads.  It is designed in such a way that the load is transmitted from the structure to the sub-structure in such a way that the strut is meant to maintain the rigidity of the structure.
Columns are the compressive members of the frame structure. Struts are the compressive member of the truss structure.
In the case of columns, loads are applied anywhere throughout the column. In the case of the strut, loads are always applied at joints on the strut.
It is designed to take the heavy compressive load only.  Struts are designed in such a way that to take up a small both compressive as well as tensile load.
Columns are generally supported by fixed supports at both ends. Struts are generally supported by hinged or pin joints at both ends. 
These are generally failed by buckling.  These are generally failed by crushing. 
The cross-sectional dimensions or slenderness ratio of columns is always more than the strut. The cross-sectional dimensions or slenderness ratio of a strut is always less as compared to the column.
A column is Subjected to gravity loading. A strut is not subjected to any gravity loading.
Columns are generally used in concrete and steel buildings. Struts are mostly used in roof and bridge trusses.


So here you have to know the column and strut, their types as well as the difference between the column and strut.

I hope you will learn all aspects related to column and strut if you have any doubt then you are free to ask me by mail or on the contact us page.


Thank You.

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