STAAD.Pro Help

M. To calculate the structure frequency

To calculate the frequency of the structure for a load case, use the following procedure.

Frequency calculation is made for a specific load case, so you must have at least one primary load case added to the input file.
This can be done by either the Rayleigh method or the eigenvalue extraction method. The latter can consider missing mass mode.
  1. Either:

    On the Loading ribbon tab, select the Load Items tool in the Loading Specifications group

    Tip: This will add the load item to the currently selected load group selected in the program status bar.


    In the Load & Definition dialog, select a primary load case in the Load Cases Details list and then click Add.

    The Add New Load Items dialog opens.
  2. Select either:

    the Frequency > Rayleigh Frequency tab to use the approximation method


    the Frequency > Modal Calculation tab to use the more exact eigenvalue extraction method

  3. (Optional) For Modal Calculation, check the Consider Missing Mass option to include the missing mass procedure for steady state or harmonic analysis.
  4. Click Add. The frequency calculation is added to the load case.