A. To generate a floor spectrum

To calculate the floor spectra from time history acceleration, use the following procedure.

This procedure should only be used if a time history load case is being solved by the analysis engine.

Note: The floor response spectrum command must immediately follow an analysis command. Therefore, it is helpful to select the corresponding analysis command prior to starting this procedure.

Note: That analysis can only contain a single time history load case.

This command is used to specify the calculation of floor and/or joint spectra from time history results.

Note: This requires a STAAD.Pro Advanced license.

Either:

select the Analysis page

or
on the Analysis and Design ribbon tab, select the Analysis Commands tool in the Analysis Data group

The Analysis/Print Commands dialog opens.
Select the Generate Floor Spectrum tab.
For every group and direction that is necessary:
1. Check one or more global directions in a table row: GX, GY, and GZ.
2. Type a Title used to identify the spectrum.
3. Use the drop-down to select the Node Groups which are included in this direction.
You may include as many directions as needed.
(Optional) Type frequency options to use for the spectra (all are optional inputs):
1. Type the Lowest Frequency (in Hz) to be in the calculated spectrum. This should be at least 0.0 Hz.
2. Type the Highest Frequency (in Hz) to be in the calculated spectrum
3. Type the number of Frequency Interval to use between the lowest and highest frequency.
(Optional) Type up to ten Damping Ratios to use as a ratio. (e.g., 3% damping is 0.03) One spectrum will be generated for each damping ratio for each global direction requested for each floor defined. The spectrum will be based on these damping ratios. Is not entered, the default of 5% (0.05) damping will be used as a single damping ratio.
Check the Relative Acceleration? option if there is ground motion defined and you wan tthe spectrums based on the relative acceleration of the floor to the ground acceleration. Otherwise, the acceleration is assumed to be an absolute acceleration.
(Optional) Select the print parameters as needed (both are optional):
1. Check the Print Time History Acceleration used? option to include this in the output.
2. Check the Print Calculated Spectrum? option to include this in the output.
Select the Print Option you want to use.
Click Add.
Tip: The After Current option is helpful to make sure this is added immediately following the analysis command if you selected prior to this procedure.
The generate floor spectrum command is added to the input file.