All cross-sections available in the model are listed again in the Input Data of the design add-on.
Allowable Cross-Sections
The font color of the cross-section gives you the information about the utilization and validity of a cross-section in the selected design add-on:
- Blue = a cross-section not used in the entire model
- Red = a cross-section not suitable for design in the active add-on
- gray = objects with this cross-section are not selected for design in the active add-on
- black = objects with this cross-section are selected for design in the active add-on
In the steel design, only cross-sections with materials of the Steel type are allowed (see also Chapter Materials). Furthermore, there are restrictions regarding the cross-section type. Regardless of the selection in the "To Design" check box, objects with invalid materials are not considered in the design (an automatic classification in "Not Valid / Deactivated").
Removing Cross-Sections from Design
For all valid cross-sections, you can deactivate all objects with this cross-section by clearing the "To Design" check box. Thus, these objects are assigned to the "Not Valid / Deactivated" column and removed from the design (see Objects to Design).
Section Type
The section type of a cross-section provides the information about the possible design. Some cross-section types are not allowed for the design in the add-on or can only be used with restrictions. The following cross-section types are allowed in the Steel Design:
- Standardized - Steel
- Parametric - Thin-Walled
- Parametric - Bars
- Built-up - Steel
- General by RSECTION
Cross-Section Classification (for EN 1993 only)
This column is only available if you select the design standard EN 1993. By default, the automatic cross-section classification is activated, provided that there is a subpanel available for the cross-section type. The c/t ratios of the existing subpanels are checked and the classification is carried out automatically in cross-section classes 1-4.
If no subpanels for local buckling are defined for a cross-section in accordance with the selected design standard, the cross-section is automatically classified as Class 3 and then designed elastically. A check of the c/t ratios and designs for local buckling are then not possible.
Select the "Class 1/2" option to obtain the design with the plastic section resistances without further checking the c/t parts. Select "Class 3" for an elastic design where no additional check for local buckling is to be performed. The "Class 4 possible" option allows for checking whether the effective section properties have to be taken into account. Depending on the result, the cross-section is classified in Class 3 or Class 4 and designed accordingly.
Design of Cold-Formed Sections (for EN 1993 and AISC only)
Cold-formed sections usually require special design checks of local buckling and cross-section stability. If a cross-section has the "cold-formed" manufacturing type and has been selected as the EN 1993 design standard, the checks for objects with this cross-section are automatically performed according to EN 1993‑1‑3 (except for cold-formed hollow sections). When selecting the AISC 360 standard, the cold-formed sections are designed according to AISI S100. For other design standards, no special design of cold-formed sections is currently implemented.
Adjusting Cross-Sections
Section properties can be adjusted in the editing dialog box of the cross-section. Double-click a row or click the
button to go directly to the editing dialog box of the cross-section.
The "Options" column includes the icons for various existing settings or modified values, so you can quickly get an overview and, for example, identify the cross-sections calculated according to the thin-walled theory.
To create and design any cross-section, you can use the RSECTION program.
Notes on Stress Determination
If stress-based design checks are performed for a cross-section, the required stresses are determined according to the analysis method selected in the cross-section. Select the "Thin-walled model" option for a cross-section to determine all cross-section properties and stresses used for the design according to the thin-walled analysis. If this option is not activated, the determination of the cross-section properties and stresses is based on the FE solution.
To verify the stress values used in the design, you can use the unit stresses of the corresponding analysis method as a basis. They are displayed in the editing dialog of the cross-section.
Further information on stress determination and the analysis methods used can be found in the corresponding chapters of the online manual for the RSECTION program.
Notes on Design of RSECTION Cross-Sections
The options for designing cross-sections from RSECTION depend on the selected cross-section modeling. If a cross-section has elements, subpanels are generated automatically that allow for the calculation of the effective cross-section properties. If no elements but only parts are defined in the cross-section, no subpanels can be created and an automatic cross-section classification is not possible.
Using Different Cross-Section for Design
If you want to use a different cross-section for the design than for the RFEM calculations, you can select the cross-section to be used for each cross-section. This does not affect the internal forces, which are also used for the design of the other cross-section.
If a different cross-section is entered in this column, further options are available in the shortcut menu (Export Section to RFEM, Export All Sections to RFEM, Import Section from RFEM, Import All Sections from RFEM).
Simplified Cross-Section Optimization
For standardized cross-sections, it is possible to optimize the cross-sections from their respective series of the cross-section library. In this case, the program searches for the smallest possible cross-section from the corresponding row, for which all design checks provide a smaller design criterion than the limit value defined in the Global Settings.
For this simplified cross-section optimization of the standardized cross-sections, the same boundary conditions apply as for using another cross-section for the design. With the given internal forces, the design checks are carried out for all cross-section variants to be optimized and then the optimal variant is displayed.
Therefore, the final design requires transferring the optimized cross-sections to RFEM and performing the calculation again. Comprehensive structural optimization is only possible with the Optimization & Costs / CO2 Emission Estimation add-on.