Effective Lengths and Factors

For members, when you apply the eigenvalue analysis (see Stability Analysis Type), you obtain the following results for each eigenvalue:

Critical Load N_cr

… corresponds to the acting axial force from the structural analysis multiplied by the (global) critical load factor. The calculation considers the average axial force in the member, not the maximum axial force. It is necessary to classify the results accordingly, especially for undivided members with a discontinuous axial force distribution.

Effective Length L_cr

… is calculated from the critical load N_cr, assuming an ideal compression member (Euler Buckling Mode II) with hinges on both sides:

Effective Length Factor k_cr

… sets the effective length of a member L_cr in relation to the actual length of the member L:

Modal Relevance Factor MRF

… describes the relevance of a member for the occurrence of a specific mode shape and provides notes on how to distinguish between global and local mode shapes.

For more information on using the MRF, refer to our Knowledge Base.

Image Grouping of Results:

Result Display – Member Number and Mode Shape