Set up global imperfections

Notional horizontal forces can be included in load combinations to cater for global imperfections.

They are set up for the current model via the Global Imperfections page in Model Settings. The way they are defined depends on the code being worked to:

For USA - see Notional loads (NL) (ASCE 7)
For Eurocode - see Equivalent horizontal forces (EHF) (Eurocode)
For British Standards - see Notional horizontal forces (NHFs) (British Standards)
For Australian Standards - see Notional horizontal forces (NHFs) (Australian Standards)
For Indian Standards - see Notional horizontal forces (NHFs) (Indian Standards)

Create global imperfections

Horizontal forces to cater for global imperfections are set up as follows:

On the Home tab, click Model Settings.
In the Model Settings dialog box, click the Global Imperfections page.
Specify the parameters as required for the regional code being worked to.
Click OK.

The global imperfection loadcases are set up according to the parameters specified in Model Settings and are listed as available loadcases on the Combinations page of the Loading dialog box.

Include global imperfections in load combinations

Once the global imperfections have been set up, they can be included in load combinations as follows:

On the Load tab, click Combination.
The Loading dialog box opens on the Combinations page. On this page, you can see all currently existing load combinations.
If you are manually creating combinations:
- the global imperfections for each direction will appear in the list of available loadcases for inclusion. For example, if working to the United States codes 'NL' loadcases would appear as below. (For EC these would be 'EHF' loadcases, and for other codes 'NHF' loadcases.)
- You can then select the appropriate global imperfection loadcase for each combination as required.
- If you are automatically generating combinations, as you proceed through the Combination Generator, a global imperfections page is displayed. The page will be titled according to the code being worked to, ('NL' for US as below, 'EHF' for EC, or 'NHF' for other codes). On this page you specify the direction(s) in which the load is to be applied and the accompanying factor(s).
If you are automatically generating combinations:
- As you proceed through the Combination Generator, a global imperfections page is displayed. The page will be titled according to the code being worked to, ('NL' for US as below, 'EHF' for EC, or 'NHF' for other codes).
- On this page you specify the direction(s) in which the load is to be applied and the accompanying factor(s).
Click OK to close the Loading dialog box.

Review global imperfections

The global imperfections (NL/EHF/NHF) are automatically calculated and applied during analysis. You can display their magnitude and direction graphically in a results view via the “NL/EHF/NHF ” button in the Notional/ Seismic Loads group of the ribbon.