In this dialog box, you can make the basic specifications for the ultimate limit state design. The basic structure of the dialog box for design configurations and the possibility of assigning them to the individual objects are described in the chapter Aluminiumbemessung chapter.
Main
In the Main tab, you can make various settings that affect the aluminum design.
General
The "Perform stability design" check box controls whether stability design checks are carried out in addition to the cross-section design checks. Deactivate this check box if you do not want to perform the stability design or if you have already considered the stability effects in the internal forces determination (for example, a calculation according to the second-order or large deformation analysis with imperfections and/or stiffness reduction, validity, and other settings depending on the design standard).
If stability design is activated, it is necessary to specify effective lengths for the respective objects. If they are not assigned, a warning message appears in the result table of Errors & Warnings. Cable members and tension members are excluded from this warning, as only tensile forces can occur there by definition, and thus no stability design is required.
Limit Values for Special Cases
The design standards, which are often based on a manual calculation, often only allow design formulas or interaction conditions for certain combinations of internal forces. Within the context of a structural calculation on a 3D model, small values are often obtained for internal forces, which are not important for the load-bearing capacity from an engineering point of view, but which prevent certain design design checks or necessitate the use of less favorable interaction formulas if the design standard is strictly observed. Therefore, the Limit Values for Special Cases option provides a simple and transparent way of neglecting certain internal forces in the design in order to avoid the problems mentioned above.
The definition is done by specifying the plastic section resistance component, which is determined in a simplified way via the cross-section properties. These are not design resistances regulated in a standard, so no standard-specific regulations (for example, for cross-section classification) are taken into account, as this does not correspond to the purpose of the limit value setting. Therefore, you should only use high limit values for testing purposes.
If an internal force is within the limit values, there is no further warning saying that it has been neglected now. In Design Check Details, the comment "Negligible" next to the respective internal force allows you to easily check which internal forces have been neglected due to the limit value settings and not considered in the design. If all internal forces are negligible at one location, the design check of the negligible internal forces is displayed at this location.
In case you have activated the Torsional Warping (7 DOF) add-on, a limit value for the bimoment and the shear stresses due to the secondary torsion is also available for some design standards.
Further Options
Depending on the selected design standard, further options are available in the ultimate configuration. For example, there are the options to activate elastic cross-section design for all cross-sections, alternative values for form factors and exponents, or further detailed settings for local buckling and design of shear buckling.
Stability
The Stability tab is available if Stability Analysis has been activated in the Main tab. Depending on the selected design standard, you can define further settings for the stability analysis here.
Load Application Point
If transverse loads are available, it is important to define the location where these forces are acting on the cross-section: Depending on the load application, transverse loads can be stabilizing or destabilizing, and thus have a major impact on the elastic critical moment for lateral-torsional buckling Mcr.
Further Options
Depending on the selected design standard, further settings are available, such as the alternative methods for determining slenderness.
Standard Parameters
For the design standard EN 1999, all relevant coefficients conforming the selected National Annex are listed in the Standard Parameters tab. To enter a user-defined value, adjust the value in the corresponding text box. Use the button
to reset the values to the default values of the selected National Annex.
