M. To add a seismic load

To add a seismic load to a primary load case, use the following procedure.

Note: You must have at least one seismic load definition in your model before you can add seismic loads.

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.
Select the Seismic Loads tab.

Note: If you do not have a seismic load definition created, this tab is disabled.
Select the global Direction in which this seismic load acts.
Optional: Type the scale Factor to apply to the load.
Optional: Check the option to use Multiplying factor for Accidental Torsion Moment and type a Factor.
This value is the ratio of the total building width and is taken from the center of mass for each level.
Optional: Check the option to use Multiplying factor for Natural Torsion Moment and type a Factor.

Note: This is only applicable for structures modeled with a rigid diaphragm.
This torsion -referred to as the natural torsion- accounts for the static eccentricity which is the difference between center of mass and center of rigidity of a rigid floor diaphragm
Click Add.