2.1.1 Ultimate Limit State

Ultimate Limit State

This column lists all load cases, load combinations, and result combinations that have been created in RFEM or RSTAB.

To transfer selected entries to the Selected for Design list on the right, click the button. Alternatively, you can double-click the entries. To transfer the entire list to the right, use the  button.

As common for Windows applications, selecting several load cases is possible by clicking them one by one while holding down the [Ctrl] key. Thus, you can transfer several load cases at the same time.

If a load case's number is marked in red such as LC8 in Figure 2.5, you cannot design it: It indicates a load case without load data, or a load case that contains imperfections. A warning appears if you try to transfer it.

Below the list, several filter options are available. They help you assign the entries sorted by load case, load combination, or action category. The buttons have the following functions:

Table 2.1 Buttons in Ultimate Limit State tab

	Selects all load cases in the list.
Inverts selection of load cases.

The column on the right lists the load cases as well as load and result combinations that have been selected for the design. To remove selected items from the list, click  or double-click the entries. To empty the entire list, click .

You can assign the load cases, load and result combinations to the following design situations:

• Persistent and Transient
• Accidental

This classification controls the partial factors γ_M0, γ_M1 and γ_M2 that are included in the determination of the resistances R_d for the cross-section and stability analyses (see Figure 2.10 ).

To change the design situation, use the list which you can access by clicking the button at the end of the text box.

For a multiple selection, press the [Ctrl] key and click the corresponding entries. Thus, you can change several entries at once.

Designing an enveloping max/min result combination (RC) is performed faster than designing all contained load cases and load combinations, but the analysis of a result combination has also disadvantages: First, the influence of the contained actions is difficult to discern. Second, for the determination of the elastic critical moment M_cr for lateral-torsional buckling, the envelope of the moment distributions is analyzed, from which the most unfavorable distribution (max or min) is taken. This distribution, however, only rarely reflects the moment distribution that is available in the individual load combinations. Thus, for an RC design, more unfavorable values for M_cr are expected, leading to higher ratios.

Result combinations should be selected for design only in case of dynamic combinations. For "usual" combinations, it is recommended to use load combinations because here the actual moment distributions are applied for the determination of M_cr.

In the General tab of the Details dialog box, you can define how result combinations of the 'OR' type are handled in the design (see Chapter 3.1.8).