Buckling

Whenever buckling analyses need to be run an eigenvalue analysis is carried out, in order to determine the modes of vibration of a structure. The Jacobi algorithm with Ritz transformation is employed by default, whereas for smaller models the direct inversion of the stiffness matrix (which is stabler) can also be performed.

Jacobi algorithm with Ritz transformation
In Jacobi algorithm with Ritz transformation the user may specify:

• Number of Ritz vectors (i.e. modes) to be generated in each direction (X, Y and Z). This number cannot exceed the number of dof.
• Maximum number of steps. The default value of 50 may, in general, remain unchanged.

Matrix Inversion
The Number of load multipliers should be defined in matrix inversion. The maximum number of load multipliers required by the user. The default value is 10. Users might wish to increase this parameter when analysing very flexible buildings.