The Sections table in the “Aluminum Design” category lists all the cross-sections you have created in the model.
Allowable Cross-Sections
The aluminum design is possible for many cross-section types. The font color of the cross-sections provides information about the use and allowability of the cross-section. The colors mean:
- Black = Members / member sets with this cross-section are selected for design in the active add-on.
- Red = a cross-section not suitable for the design in the active add-on
- Gray = Members / member set with this cross-section are not selected for design in the active add-on.
- Blue = a cross-section not used in the entire model
Furthermore, thin-walled cross-sections from the cross-section property program RSECTION can be designed (see the section RSECTION Cross-Sections). The categories of the individual cross-sections are specified in the “Cross-Section Type” table column.
Objects with an invalid cross-section are not included in the design, even if the “To Design” option is activated for this cross-section. They are automatically displayed as “Not Valid / Ddeactivated” in the Objects to Design table.
Removing Cross-Section from Design
For a valid cross-section, you can exclude from the design all objects with this cross-section assigned by clearing the "To Design" check box. Thus, these objects are classified as "Not Valid / Deactivated" in the Objects to Design table and not analyzed in the design.
Adjusting Cross-Section
If necessary, you can adjust the cross-section properties in the editing dialog box. To do this, double-click in the cross-section row or click on the
button in the table toolbar.
The “Options” table column includes icons for various existing settings or modified values (see the image Input Table for Cross-Sections). They allow for a quick overview of the cross-sections used. The icon
, for example, is assigned to all cross-sections that are calculated according to thin-walled theory.
Notes on Stress Determination
The stress-based design checks of a cross-section are based on the method of analysis selected for the cross-section. If you have activated the “thin-wall analysis” for the cross-section, both the cross-section properties and the stresses used for design are determined according to the thin-wall analysis (“TWA”). If this option is not activated, the cross-section properties and stresses are determined based on an FEM solution.
The unit stresses for the respective stress determination provide a good basis for understanding the stress values used in a design. You can check these in the cross-section editing dialog box.
RSECTION Cross-Sections
The options for the design of cross-sections in the RSECTION program depend on the modeling of the cross-section: If the cross-section contains elements, single panels (b/t parts) are automatically generated, which allow for the calculation of the effective cross-section. However, if the cross-section is defined by parts without elements, single panels cannot be created. Automatic cross-section classification is then not possible. Furthermore, the thickness of the individual cross-section parts cannot be determined, so that the design is carried out using the material properties of the first thickness range.
Using Another Cross-Section for Design
You can use a different cross-section for the design than for the RFEM calculations: To do this, click in the corresponding row of the “Use Other Section for Design” table column. You can then import a cross-section from the library using the
button.
If a different cross-section is entered in the column, additional options are available in the shortcut menu. You can use these options to transfer the new cross-section to RFEM so that it is also used in the structural analysis. It is also possible to import the original cross-section back into the table.
Optimizing Cross-Ssection
The Aluminum Design add-on provides the option of optimizing standard cross-sections. Using this simplified optimization, the program searches for the smallest possible cross-section within the same cross-section series that fulfills all design checks with a design criterion smaller than the maximum allowable design ratio specified in the Global Settings dialog box.
To optimize a cross-section, click on the corresponding row in the “Use Other Section for Design” table column. Then, select the “Optimize” option from the list.
For a parametric cross-section, the editing dialog box for the cross-section appears. In the “Optimization | Aluminum Design” tab, you can specify the parameters for the optimization.
In the “Geometry” column, select the parameter(s) you want to change. You can then enter the lower and upper limits for the parameter in the “Min” and “Max” columns. The “Step” controls the interval in which the dimensions of the parameter vary during the optimization process. If you want to “Maintain aspect ratios,” select the corresponding check box and specify the parameters for optimizing the external dimensions.
The same conditions apply to cross-section optimization as when using another cross-section (see above). The design checks are performed for all cross-section variants with the internal forces of the structural analysis. The optimal variant is then displayed in the table column. The effects of the changed cross-section on the stiffnesses and internal forces in the RFEM model are not taken into account. Therefore, use the options in the shortcut menu to transfer the optimized cross-sections to the RFEM model (see the image Shortcut Menu with Export or Import Options).
Comprehensive structural optimization is possible with the Optimization & Cost / CO₂ Emission Estimation add-on.