Auto Load Combination dialog

Used to automatically create load combinations based on code-specified combination rules and primary load type selections.

In order to use this feature, one or more primary load cases must be created with a load type defined. A load type can be assigned to a primary load case either at the time when the load is being created or later.

Opens when the Automatic Combinations > Automatic Load Combinations tool is selected in the Load Generation group on the Loading ribbon tab.

Note: If no load cases have yet been defined for the model, a warning message is displayed over the dialog and the parameters are inactive. Primary load cases are defined using the Create Primary Load Case dialog.

Setting

Description

Select Load Combination Code

The load types available include the following:

ACI:318-2002
AISC 9th Ed
ASCE 7-10
BS:5950
BS:8110
GB:50009-2012
GB:55002-2021
IBC-2012
IBC-1997
NBCC-2005
NBCC-1995
IS:456 / IS:800
SNiP 2.01.07-85
UBC-1997
ASCE 7-16

Note: Any Load Rule sets you have added or edited in the Edit Load Rules for Auto Load Combination Generator dialog are also available here.

Select Load Combination Category

Select the load combination category as specified in the selected load combination code. Refer to the selected code for details.

Select Starting Combination No

Type an integer for the initial load combination number. This number should not be a current load case number.

Create Repeat Load Cases

Select this option to create primary load cases for all the load case combinations in the Selected Load Combinations list using the Repeat Load Command, rather than combined results using Load Combinations.

See GS. Load Types in STAAD.Pro for additional information on using Repeat loads versus Load Combinations.

Include Notional Load

Select this option to include Notional Load cases in the generated combinations when the Create Repeat Load Cases option is selected, if they are present in the input file.

Setting

Description

Factor

Type the notional load factor to use

Use Floor Count

Optionally, you may select to use the floor count to determine the notional load factor by checking this option and typing the floor count value. This method is adapted from the Chinese GB50017-2017 code and uses the following formula modified from Cl. 5.2.1-2:

factor = \frac{A}{250}

where:

$\frac{2}{3} \leq A = \sqrt{0.2 + \frac{1}{n_{s}}} \leq 1.0$

n_s = the number of stories

Direction

Check the directions for which to generate notional loads: X, -X, Z, and -Z.

Generate Loads

Click to create all the load combinations. The generated load combinations, with their associated load factors, are shown in the Selected Load Combinations list on the right-hand side.

Discarded Load Combinations

Any load combinations which are generated can be removed from the final load combination. These will be listed here.

list operators

Click this button…	to…
>	Add the selected primary load case to the Selected Load Combinations list
>>	Add all primary load cases to the Selected Load Combinations list.
<<	Remove all entries in the Selected Load Combinations list, load combination is placed in the Discarded Load Combinations list.
<	Remove the selected entry from the Selected Load Combinations list.

Selected Load Combinations list

All load combinations which will be added to the input file are listed here.

Automatically Generated Load Combinations in the STAAD input file

In the STAAD.Pro Input File, the generated load combinations look like the following:

UNIT FEET KIP
LOAD 1 DEAD + LIVE
MEMBER LOAD
2 UNI GY -2.5
LOAD 2 WIND FROM LEFT
JOINT LOAD
2 FX 10
LOAD COMB 3 Generated AISC 1
1 1.6
LOAD COMB 4 Generated AISC 2
1 1.4
LOAD COMB 5 Generated AISC 3
1 1.7 2 0.8
LOAD COMB 6 Manual
1 1.7 2 -1.2
PERFORM ANALYSIS
PRINT MEMBER FORCES

The syntax Generated xxx n, where xxx is the design code name (AISC, BOCA, etc.) and n is the index in the series of load combinations generated for a specific code, are interpreted by STAAD.Pro. Deleting any of the aforementioned keywords will break the program’s ability to read back in the generated load combinations.

The following are some important caveats to keep in mind when using the automatic load combination generator:

If the automatically generated load combinations are edited (or deleted) from the STAAD input file, they will be reflected in the graphical interface as well.
The load combination numbers (i.e. LOAD COMB n GENERATED AISC 1) can also be edited from the input file.
Deleting the keyword GENERATED code index will remove that particular load combination from the automatically generated list. It will not remove the load combination.
The factors assigned to the primary load cases in a generated load combination cannot be changed in the graphical interface using the Combine button from the Loads dialog box.