Applies To
	Product(s):	STAAD.Pro
	Version(s):	All
	Environment:	N/A
	Area:	Modeling Solutions
	Subarea:	Loading
	Original Author:	Bentley Technical Support Group

Reference Loads is a powerful tool in STAAD.Pro that expands users’ options for setting up load cases and improves their overall efficiency. Reference Loads are useful because they are not explicitly solved during the analysis, but rather exist only as building blocks to be included in creating primary load cases. In this sense one can think of Reference Loads as “load definitions.”

They are particularly helpful for large models, which often contain many load cases that do not require analysis in their own right, including seismic, wind, or live load acting alone. Users can create multiple reference loads and then have STAAD.Pro solve only a limited number of “real” load cases. By limiting the loads examined, the user can significantly reduce the time required for analysis.>

Reference Loads are defined in the Loading page of the Analytical Modeling workflow:

 

In the Definitions section, the Reference Loads are listed as follows:

 

To add a new Reference Load case, select "Reference Load Definitions" in the Load & Definition dialog box and click Add. Inputting the title for the Reference Load case and the number is done in the same manner as when creating primary load cases.

Once a Reference Load case has been created, follow these steps to input load items. This process, too, is exactly the same as for primary load cases:

1. Select a Reference Load to highlight it,
2. Click Add to open the Add New Reference Load Items dialog box, 
3. Define the load items, selecting from the list of loads on the left,
4. Assign the load item to the appropriate entities (nodes/members/etc.) in the model.

 

At this point the Reference Load definition is complete. The next step is to include the Reference Loads in primary load cases, as follows:

1. Select a primary load case and click Add,
2. Click the load item Repeat Load -> Reference Load,
3. Select the required defined Reference Load cases and click [>] to include them in the current primary load case. Clicking [>>] will include all defined Reference Load cases. You can add appropriate combination factors for each reference load.

 

The format of the definition of a Reference Load (i) in the data file is as follows:

DEFINE REFERENCE LOADS

LOAD R(i) LOADTYPE (type) TITLE REF LOAD CASE 1

(Load items)

....

END DEFINE REFERENCE LOADS

The format of a reference to a Reference Load in a primary load (j) case is as follows:

LOAD (j) LOADTYPE (type) TITLE LOAD CASE 1

REFERENCE LOAD

R(i) 1.0

Reference Loads are very helpful when creating a seismic load definition. Consider, for example, a situation in which the dead loads have been defined as Reference Loads. Instead of manually inputting the dead loads a second time in the seismic definition, you can simply refer to the Reference Load case, which is listed in the seismic definition dialog box as seen below.