A column is a compression member that is mainly designed to transfer compressive loads. They are considered the vertical load-carrying elements of a building.

 R.C.C Column

Consider a perfectly straight vertical column subjected to an axial load. With the increase in the axial load, the column goes through three conditions

Â· Stable equilibrium
Â· Neutral equilibrium
Â· Instability

The stable equilibrium condition exists when the vertical column is subjected to a lateral force between the two ends of the column which in turn results in a small lateral deflection that vanishes when the lateral force is removed.

Next, the lateral load is increased again till a condition is reached when removal of lateral load wonâ€™t result in recovery to the initial condition. This is the condition where the column is bent slightly when the load is removed. This condition of the column is in neutral equilibrium. The load at which the column reaches neutral equilibrium can be called as a critical or buckling load.

Next, the state of Instability is reached when the load beyond critical load would cause uncontrollable lateral deflections that are permanent and would result in complete collapse.