nastran manual


Load Cases

One load case is a group of one ore more loads assigned to entities. When a new model is defined in GiD-NASTRAN Interface a default load case, called Load case 1, is defined. It is possible to rename this loadcase or define new ones by using the loadcase button in the toolbar or in the load cases window.

When a load is assigned to one or several entities, this load is inserted inside the loadcase that is currently active. To make a loadcase active, select it in the loadcase menu in the toolbar or in the loadcases window. To show which load case is currently active, the loadcase button changes to reflect the load case number.

If combined load cases are not defined, GiD-NASTRAN Interface calculates just one analysis that is equivalent to that of all the loads belonging to one load case.

Combined load cases

Pentágono: Load cases 
Pentágono: Data

 

Combined load cases are defined in the load cases window

Options are:

Prestress model: Some NASTRAN codes offer the possibility to simulate models affected by a pre-stiffened or pre-stressed load case. The basic idea is to run a first combined loadcase that will contain all the simple loadcases used to calculate pre-stress in the model and another combined loadcase with the post-stress load.

One result for every loadcase: One combined loadcase is created for every simple loadcase. It is possible to enter amplification factors for every loadcase. This option is equal to run so many models as loadcases defined.

Use combined loadcases: User can define as many loadcases as needed. It is possible to enter amplification factors for every combination of simple loadcases in combined loadcases.

When using combined loadcases, one default combined loadcase is already existent. To create more, press right mouse button over the existent combined load case name. A menu appears that offers several options.

 One factor must be entered for every simple loadcase. This factor will multiply the load in order to create the combined loadcase. In the postprocessing part, after the analysis, there will be one different result for every combined loadcase. Enter value 0.0 in order to deactivate that loadcase.

It is also possible to choose the same constraints for combined loadcases. Sometimes this option can be very useful because when there are only changes in loads distribution and the constraints are always the same.