5.6.1 User-Defined Combinations
There are several ways to open the loading dialog box for creating a result combination:
- Menu option Insert → Load Cases and Combinations → Result Combination
- [New Result Combination] button in the toolbar
- Shortcut menu of the Result Combinations navigator entry
The Edit Load Cases and Combinations dialog box appears. A new result combination is preset in the Result Combinations dialog tab.
The following description refers to the General tab. The Calculation Parameters dialog tab is described in Chapter 7.3.2.
- It is also possible to enter a new result combination in an empty row of Table 2.6 Result Combinations.
The number of the new result combination is preset but can be modified in the RC No. text box. The order of the result combinations can also be adjusted retroactively with the [Renumber] dialog button (see Table 5.8 and Chapter 11.4.18).
You can enter any name manually or select one from the list to briefly describe the result combination. As manually entered descriptions are stored in the list, they are also available for other models.
Use the check box to control if the result combination is considered in the calculation. In this way, it is possible to exclude result combinations from the calculation or reactivate them.
The columns provide information about the load cases, load combinations, and result combinations, including related factors.
The values indicated in the Factor table column are based on the coefficients that depend on the selected standard, among other things. For EN 1990, they are the partial safety factors γ, the combination factors ψ, the reduction factors ξ, and, if applicable, the reliability factors KFI of each action, which result from design situation and action category.
To check and, if necessary, adjust the partial safety factors and combination coefficients conforming to standards, use the [Details] dialog button. The Coefficients dialog box opens where you can find various factors, organized in several tabs. The Partial Safety Coefficients tab for EN 1990 is shown in Figure 12.27. The Combination Coefficients tab manages the factors ψ and ξ (see Figure 5.24). The reliability factor KFI can be defined in a list in the Consequence Classes dialog tab, but you can also enter a user-defined value.
In the Edit Load Cases and Combinations dialog box, you can superimpose load cases, load combinations, and result combinations in a combination as follows: Select the relevant entries in the Existing Loading list by clicking them. As familiar from MS Windows, you can use a multiple selection by pressing the [Ctrl] key (see Figure 5.42). Use the and dialog buttons to transfer the selected entries into the Loading in Result Combination list to the right.
The load case factors are applied according to the standard set in the Model - General Data dialog box. If required, you can adjust the preset partial safety factors (see Chapter 12.2.1) by using the [Edit Settings] dialog button.
To remove a load from a result combination, select the load case in the Load Cases in Load Combination column of the dialog box. Use the button or double-click the entry to return it to the Existing Loading dialog section.
The load cases, load combinations, and result combinations contained in the result combination can be superimposed in accordance with their effect:
- Loading Criterion
- Permanent Effect
- If you want to apply the loading permanently or unconditionally, the Permanent criterion or /p must be added to the loading.
- Variable Effect
- A loading with the Variable criterion is only considered in the superposition if its internal forces make an unfavorable contribution to the result.
- Criterion for Superposition
- Additive Combination
- The results of loadings are combined additively with the "+" criterion. Use the button in the dialog box to transfer the marked load cases, load combinations, and result combinations into the definition list of the result combination.
- Alternative Combination
- For the alternative analysis using the "or" criterion or the abbreviation "o", RFEM treats the results of particular loadings as mutually exclusive. RFEM only considers the values of the loading that makes the maximum unfavorable contribution. Use the dialog button to transfer selected loadings to the definition list of the result combination.
- Loadings that act alternatively are marked with the same number in the Group table column.
- The criterion "orto" ("or to") combines a list of alternative loadings from the first to the last object. Objects that lie in-between are not listed.
- All loadings listed in the alternative combination group must be uniformly marked as 'Permanent' or 'Variable'. Thus, it is not allowed to, for example, enter "LC1/p or LC2".
It is possible to individually adjust the factors of transferred loadings: Select the loading(s) in the Loading in Result Combination list, and then enter a suitable factor into the text box or select it from the list. Finally, click the [Set Factor] button to apply the new factor to the loading(s).
Analogously, you can retroactively change the loading criterion (permanent or variable effect) or the group affiliation of an alternative loading. To assign the new criterion to the selected loading, use the [Set] dialog button.
Several filter options are available below the Existing Loading list. With their help, it is easier to assign loadings sorted by load cases, load combinations, action combinations, and action categories. In addition, it is possible to restrict the listing to unassigned loadings. The buttons are described in Table 5.8.
You can manually define result combinations in a separate dialog box by using the [Edit] button in the bottom right of the Edit Load Cases and Combinations dialog box.
In the Loading in Result Combination text box, load cases can be added with any factor or combined with the "or" criterion. Nesting of input is not permitted.
- LC1/p + LC2/p + LC3
- Load cases 1 and 2 are superimposed as permanent, load case 3 as variable.
- LC1/p + CO2 + LC3 or LC4 or LC5 (corresponds to LC1/p + CO2 + LC3 orto LC5)
- Load case 1 is considered permanent in the superposition and load combination 2 variable. The most unfavorable among load cases 3, 4, or 5 is also variably superimposed with the criterion (i.e. only one of them is effective - if it increases the result values).
- 1.2CO1/p + 0.2RC1 or -0.2RC1
- The 1.2-fold of load combination 1 is superimposed as permanent with the most unfavorable contribution of the positive or negative 0.2-fold of result combination 1.
- RC1/p o RC2/p o RC3/p o RC4/p (corresponds to RC1/p orto RC4/p)
- Result combinations 1 through 4 are compared among each other as permanently acting. The envelope is determined as the most unfavorable result.
Use the [Set] button to transfer the entry into the Loading in Result Combination list of the initial dialog box.
Enter a user-defined note or select an entry from the list to describe the result combination in detail.
The Calculation Parameters tab in the Loading dialog box provides different options for controlling the calculation. You can find a detailed description of these parameters in Chapter 7.3.1.
There are several ways to change result combinations retroactively:
- Menu option Edit → Load Cases and Combinations → Result Combinations
- Shortcut menu or double-click of a result combination in the Data navigator
In the Edit Load Cases and Combinations dialog box (see Figure 5.40), select the RC by clicking it. Then you can edit the definition criteria.
In the Edit Load Cases and Combinations dialog box, several buttons are available below the Existing Result Combinations and Existing Loading lists. The buttons have the following functions:
Creates a new result combination.
Creates a new result combination as a copy of the selected combination.
Assigns a new number to the selected result combination, which must be specified in a separate dialog box. It is not allowed to enter an RC number that has already been assigned.
Deletes the selected result combination.
The list only shows load cases not contained in the result combination.
Selects all load cases in the list.
Inverts the selection of load cases.