# Steel resistance of cross sections¶

The task Resistance of Cross-Sections contains:

Selection tab

Design tab

Control Parameter

Text output

Graphical output

Tip

If you click on the figure it will show up in original size.

See also

The task **Steel - Resistance of Cross-Sections** was explained in
the Portal Frame tutorial (Analysis and Design).

## Selection tab¶

On the left side of the Selection tab, you fill find all available loadcases with an action “Design (D)”, “Accidental (A)” and “Earthquake (E)”. Next steps are necessary to define a “Design (D)”, “Accidental (A)” or “Earthquake (E)” loadcases:

Run the defined loadcases with the “Linear analysis” task

Combine the loads with the “Combine Loads” task, there you should select the type of the results “ULS - combination”

Analyze the combined loadcases with the task “Analysis of Combined loadcases”

On the right side the structural lines with a steel material will appear in the table. The “Number” column represents the number of the structural lines.

Important

β values represent the buckling factor in (y-y) and (z-z) direction.
The β factors will be taken into account only if the checkbox “Flexural Buckling”
from the Design tab is checked. This feature will do the most simple centric
buckling check. This feature is only for those customers who do not have a BDK license.
**If you have a BDK license, then please use BDK for flexural buckling check!!!
(Task Steel - Buckling Resistance of members)**

The task provides 5 types of selection.

Structural lines,

Group of elements,

Beam elements,

Truss elements.

Cable elements.

## Design tab¶

The “Design case” number represents the loadcases for results (utilisation results, cross-section classification etc.). You can also choose between the reduced output or detailed output for the Cross-Section Classification option. In the c/t tables you will find all necessary informations regarding the cross-section plates.

Choose a Design Method. As there exist several methods allowed, user may decide which Design Method should be decisive for a particular check:

### Von Mises Yield Criterion¶

This is the most general method and may be applied as a general cross-section check procedure. Even if some particular steel design code is not implemented in SOFiSTiK, you may use this general method. Stresses will be calculated and a stress-dependent cross-section class will be determined. Cross-sections of class 1-3 will be checked against Von Mises Yield Criterion while cross-sections of class 4 will be identified and marked in “red” only. An appropriate check will not be processed for class 4 cross-sections as this method is not suitable for this, i.e. only elastic resistance of cross-section will be considered.

### Linear Summation of Forces and Moments¶

This is a EN 1993-1-1 based cross-section check method. Same as during Von Mises Yield Criterion method, stresses will be calculated firstly, because they are needed to determine a stress-dependent cross-section class. Secondly, an automatic procedure will be applied - cross-sections of class 1-2 will be checked according to EN 1993-1-1, 6.2.1 (7) & Eq. 6.2; cross-sections of class 3 will be checked against Von Mises Yield Criterion and cross-sections of class 4 will be identified and marked in “red” only. Again, an appropriate check will not be processed for class 4 cross-sections as this method is not suitable for this. Therefore, cross-sections of class 1-2 will be checked plastically, cross-sections of class 3 elastically and no check will be performed for cross-sections of class 4.

### Total Interaction of Forces and Moments¶

This is also a EN 1993-1-1 based cross-section check method. The only difference to Linear Summation of Forces and Moments is that for the cross-sections of class 1-2 complex interaction formulas according to EN 1993-1-1, 6.2.8-10 will be applied. This allows for more economic design.

Note

Although only one of the methods Linear Summation of Forces and Moments or Total Interaction of Forces and Moments is chosen, the results will be printed for all 3 methods - this is useful, because you get an overview of all methods in one place and you may decide if the method you have chosen meets your expectations. The decisive value is marked in blue (if utilisation level < 1.000) or in red (if utilisation level > 1.000). The decisive value depends on the method which has been chosen.

### Nonlinear Stresses with Strain Hardening¶

This is also a EN 1993-1-1 based cross-section check method. This method is mostly intended to solve the cross-sections of class 4, when calculation of non-effective parts of cross-sections is required. This is made by applying an iterative solution. A true stress-strain curve of a material is used. It will be checked if the forces can be resisted by calculating internal forces with non-linear stress-strain curve. Only a warning, without an utilisation level, will be printed, if the resistance is not sufficient.