M. To use frequency-spectra pairs in a time history load

To instruct the program to use frequency-spectra pairs in lieu of period-spectra pairs for the time history spectrum input, use the following procedure.

Create a structure with a time history definition using the Spectrum option.

These optional commands cannot be entered via the graphical user interface. They are required to be added using the STAAD.Pro Editor.

On the Utilities ribbon tab, select the Command File Editor tool in the Utilities group.

The STAAD.Pro Editor window opens with the current STAAD input file.
After the DEFINE TIME HISOTRY command, in the SPECTRUM options, add the command FREQ.
Save the command input file and then exit the STAAD.Pro Editor.