Eigenvalue bucking analysis is used to determine the buckling modes and elastic buckling load factors of a structure.

  

Elastic critical load factor l is defined as ratio of elastic buckling load to design load. 

Modal analysis

Modal analysis is used to determine the undamped free-vibration mode shapes and natural frequencies of a structure. Modal analysis is used as the basis for modal superposition in response-spectrum and modal time-history analysis cases. Both lump mass and consistent mass assumptions are allowed to form the mass matrix.