AD Auto Load Combination Generator

Transcription

1 16 STAAD.Pro 2003, 2 nd edition Software Release Report AD Auto Load Combination Generator Purpose The new automatic load generator feature enables the user to assign load types to primary load cases (like dead, live, wind, etc.) and automatically create load combinations based on standard load combination factors from codes like UBC, IBC, ASCE, etc. Description In order to use this new feature, primary load cases must be created. When creating primary load cases, a new option to define them in a certain load category type has been included. A load type can be assigned to a primary load case either at the time when the load is being created or afterwards. To assign a load type at the time the primary load case is being created, click on the Load tab page from the General page mode. Figure 14

2 STAAD.Pro 2003, 2 nd edition Software Release Report If no load cases have yet been defined for the model, the following dialog box will appear. 17 Figure 15 If the model already contains previously defined load cases, a dialog box like the one shown below will appear. Figure 16 In both cases, one can create a new case by keeping the radio button on Create New Primary Load Case. Associate this load case with one of the load types which can be selected from the dropdown list box.

3 18 STAAD.Pro 2003, 2 nd edition Software Release Report Figure 17 The available load types are the following : Dead Live Wind Seismic Snow Rain Water/Ice Dust Traffic Temperature Imperfection Accidental Mass If you do not wish to associate the load case with any of these types, choose None.

4 STAAD.Pro 2003, 2 nd edition Software Release Report To add subsequent new load cases, click on the New Load button. 19 Figure 18 Specify the load case number, and associate the load case with one of the choices in the drop-down list, or choose None if you do not wish to associate the case with any of those. Figure 19 When a primary load case is assigned to a particular load type, it will automatically be assigned a certain load factor when included in a load combination generation. To change (or assign) the load type for a primary load case, go to Commands Loading Define Primary Load Types from the main menu.

5 20 STAAD.Pro 2003, 2 nd edition Software Release Report Figure 20 Select or edit the load type assigned to a specific primary load case using the dialog box shown in the next figure. Figure 21

6 STAAD.Pro 2003, 2 nd edition Software Release Report Once primary load cases have been assigned load types, combinations based on specific design code factors can be created. 21 To create an automatic load combination based on a specific code, click on the New Load button from the Loads dialog box and choose New Load Combination (Auto). The New Load Combination (Manual) option allows the user to create a userdefined load combination with user-defined factors. A dialog box prompting for the design code to be used in creating the load combination will appear. Figure 22 The load types available in this release include the following: AISC LRFD 3 rd Edition BOCA 99 UBC 97 UBC 94 IBC 2000

7 22 STAAD.Pro 2003, 2 nd edition Software Release Report After selecting a design code, click on the Generate Loads button 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. Figure 23 To eliminate certain generated combinations, simply select the combinations to be deleted and use the button to move them to the left column. The button discards all the generated load combinations. To accept the Selected Load Combinations, click on the Add Combinations button.

8 STAAD.Pro 2003, 2 nd edition Software Release Report In the STAAD Input File, the generated load combinations look like the following: 23 Figure 24 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. Deleting any of the aforementioned keywords will break STAAD 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.