The StaticLoads menu

Figure 1. The StaticLoads
commands

Static loads can be applied to the cross-sections of beams. The static loading consists of three applied forces and three applied moments. Learn about the sign conventions used for the loading components. The following tasks can be performed by using the commands of the StaticLoads menu: select a loading case to be applied to the cross-section, edit an exist loading case, or define a new loading case. To access these commands, the following step must be completed first.

  1. Load the problem you want to run and perform the finite element analysis.

Once this step is completed, you are ready to apply static loads to the cross-section. Select the menu StaticLoads, to reveal the options shown in fig. 1.

SectionBuilder predefines the six static loading cases that are listed in table 1. The first column lists the names of the six loading cases and the next six columns list the corresponding values of the axial force, F1, the two transverse shear forces, F2 and F3, the torque, M1, and the two bending moments, M2 and M3.

Static loading name F1 F2 F3 M1 M2 M3
UNIT_AXIAL_FORCE_F1 1.00.00.00.00.00.0
UNIT_SHEAR_FORCE_F2 0.01.00.00.00.00.0
UNIT_SHEAR_FORCE_F3 0.00.01.00.00.00.0
UNIT_TORQUE_M1 0.00.00.01.00.00.0
UNIT_BEND_MOMENT_M2 0.00.00.00.01.00.0
UNIT_BEND_MOMENT_M3 0.00.00.00.00.01.0
Table 1. The six predefined static loading cases of SectionBuilder

Select a loading case (StaticLoads→Select loading)

Figure 2. The StaticLoads→Select loading
commands

To select a loading case, invoke the StaticLoads→Select loading command. The list of defined loading cases will appear in the drop-down list, as illustrated in fig. 2. Select the loading case you want to apply to the cross-section and click OK. You are now ready to look at the results: visualize the stress field, the strain field, or display the principal axes and centers.

The first six loading cases appearing in the list are the six static loading cases predefined by SectionBuilder and detailed in table 1. The remaining loading cases appearing in the list are user-defined loading cases, named LoadingF2nF3 and LoadingNew for the example illustrated in fig. 2.

The user-defined loading cases are documented in three different files.

  1. In the input file. Figure 3 illustrates the definition of loading case LoadingF2nF3 in the input file. The syntax for the definition of loading cases is defined in the section of the user's manual detailing loading cases. The input file can be edited easily: feel free to change the values of the various loading components to define the desired loading case adequately or to change the name of your loading case. You will need to rerun SectionBuilder for the changes you made to the input file to be reflected in the analysis.
  2. In the output file. The definition of the loading case is echoed in the output file, as illustrated in fig. 4. The output file cannot be edited.
  3. In the html file. The definition of the loading case is echoed in the html file, as illustrated in fig. 5. The html file cannot be edited.

@STRESS_RESULTANTS_DEFINITION {
@STRESS_RESULTANTS_NAME {LoadingF2nF3} {
@STRUCTURE_TYPE {BEAM}
@LOADING {
@SCALING_FACTOR {10.0}
@FORCES {0.0, 1.0, 5.0}
@MOMENTS {0.0, 0.0, 0.0}
}
}
}
Figure 3. Definition of the loading case LoadingF2nF3 in the input file
Figure 4. Definition of loading case LoadingF2nF3 in the output file
Figure 5. Definition of loading case LoadingF2nF3 in the html file

Edit a loading case (StaticLoads→Edit loading)

Figure 6. The Edit loading
dialog window

While a loading case can be edited in the input file directly, it is also possible to edit loading cases by invoking the command StaticLoads→Edit loading. To edit a specific loading case, that loading must be selected first by using the StaticLoads→Select loading command. For instance, fig. 6 shows the edit dialog window that appears when invoking the StaticLoads→Edit loading command after selecting loading case LoadingF2nF3. The dialog window lists the six components of loading, three forces and three moments, along with a scaling factor that applies to all six components.

To edit a loading component,

  1. Click the name of the loading component you want to edit,
  2. Click the Edit button.

After clicking the F3 row then the Edit button, the additional dialog box shown in fig. 7 appears. Edit the value of the loading components and click OK. Proceed in a similar manner to edit the scaling factor or any other loading component. You will need to rerun SectionBuilder for the changes you made to the loading case to be reflected in the analysis.

In many cases, the analysis of the behavior of cross-sections splits into two simpler problems, the extension-bending problem and the coupled shear-torsion problem. To simplify the analysis of the extension-bending problem, it is convenient to introduce the concept of centroid; To simplify the analysis of the shear-torsion problem, it is convenient to introduce the concept of shear center. In general, SectionBuilder assumes that forces F1, F2, and F3 are applied at the origin of the axis system.

Because the At centers? flag is set to NO, see fig. 6, forces F1, F2, and F3 are applied at the origin of the axis system. This is the default assumption in SectionBuilder.

Figure 7. Edit value of shear force F3Figure 8. Edit the At Centers flag

If the axial force F1 is applied at the centroid of the section and shear forces F2 and F3 are applied at its shear center, it is necessary to edit the At centers? flag to change its value to YES. To edit this flag,

  1. Click the name of the loading component F1,
  2. Click the At centers? column header,
  3. Click the Edit button.

As illustrated in fig. 8, an additional dialog box appear. Change the value of the flag to YES and click OK. You will need to rerun SectionBuilder for the changes you made to the loading case to be reflected in the analysis.

Define a new loading case (StaticLoads→New loading)

The StaticLoads→Edit loading command is used to edit an existing loading case. To create a new loading case, use the StaticLoads→New loading command. Figure 9 illustrate the dialog window that appears when the StaticLoads→New loading command is invoked: just enter the name of the new loading case and click OK. Next, you will be prompted to edit your new loading case, because all of its loading components have been initialized to zero, as illustrated in fig. 10. You will need to rerun SectionBuilder for the new loading case to become available in the analysis.

Figure 9. the StaticLoads→New loading command dialog windowFigure 10. Edit dialog window for the new loading case