**Buckling**

**Buckling of columns **: When a slender structural member is loaded with an increasing axial compression force, the member deflects laterally and fails by combined bending and compression rather than by direct compression alone. This phenomenon is called buckling.

**Critical load ** of a structure is the load which creates the borderline between stable and unstable equilibrium of the structure or is the load that causes buckling of the structure.

**Lateral torsional buckling of beams **: Lateral torsional buckling is a phenomenon that occurs in beams which are subjected to vertical loading but suddenly deflect and fail in the lateral and rotational directions

- The buckling load of a column is proportional to the flexural rigidity of the cross-section EI and the inverse of the column length squared . Increasing the value of the second moment of area of the section I and/or reducing the length L will increase the critical load.