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5.5.1 User-Defined Combinations
There are several ways to open the Edit Load Cases and Combinations dialog box to create a load combination:
- Menu option Insert → Load Cases and Combinations → Load Combination
- [New Load Combination] button in toolbar
- Shortcut menu of Load Combinations navigator entry
The Edit Load Cases and Combinations dialog box appears. A new load combination is preset in the Load Combinations dialog tab.
The following description relates to the General tab. The Calculation Parameters dialog tab is described in Chapter 7.3.1.
- It is also possible to enter a new load combination in an empty row of Table 2.5 Load Combinations.
The number of the new load combination is preset but can be modified in the CO No. text box. The order of the load combinations can be adjusted retroactively with the [Renumber] dialog button (see Table 5.7 and Chapter 11.4.18).
You can enter any name manually or select it from the list to briefly describe the load combination. Since manually entered descriptions are stored in the list, they are also available for other models.
You can use the check box to control if the load combination is considered in the calculation. In this way, it is possible to enable load combinations or exclude them from the calculation.
The columns provide information about the load cases with the corresponding factors.
The values indicated in the Factor table column are based on coefficients that depend on the selected standard. 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 or adjust the partial safety factors and combination coefficients, use the [Details] button. The Coefficients dialog box opens where the various factors are organized in several tabs. The first tab, Partial Safety Coefficients 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 selected in a list of the Consequence Classes dialog tab, or you can enter a user-defined value.
In the Edit Load Cases and Combinations dialog box, you can assimilate load cases in combinations as follows: Select the relevant load cases in the Existing Load Cases list by clicking them. You can use a multiple selection by pressing the [Ctrl] key (as familiar from MS Windows). Use the button to transfer selected load cases to the right into the Load Cases in Load Combination list; at the same time, partial safety factors and combination coefficients are added automatically.
The factors are created in accordance with the standard set in the Model - General Data dialog box (see Chapter 12.2.1).
To modify the coefficient of a load case that has been transferred into a load combination, select the load case in the Load Cases in Load Combination list. Now you can enter the appropriate factor into the text field below or select it from the list. Click the [Set Factor] button to apply the new factor to the load case.
To remove a load case from a load 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 Load Cases column.
Several filter options are available at the bottom of the Existing Load Cases list. These options make it easier to assign the load cases sorted by action categories or to select them from load cases that are still unassigned. The buttons are described in Table 5.7.
To manually define load combinations, use the [Edit] button in the bottom right corner of the Loading dialog box.
In the Load Cases in Load Combination text box, load cases can be added (or subtracted, if necessary) by any factor. Nesting of input is not permitted.
LC1 + 0.5*LC3
Use the [Set Input] button to transfer the entry to the Load Cases in Load Combination list of the initial dialog box.
Enter a user-defined note or select an entry from the list to describe the load 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 load combinations retroactively:
- Menu option Edit → Load Cases and Combinations → Load Combinations
- Shortcut menu or double-click of a load combination in the Data navigator
In the Edit Load Cases and Combinations dialog box (see Figure 5.31), select the CO by clicking it. Then you can edit the definition criteria.
In the Edit Load Cases and Combinations dialog box, there are different buttons below the Existing Load Combinations and Existing Load Cases lists. The buttons have the following functions:
Creates a new load combination.
Creates a new load combination as a copy of the selected combination.
Assigns a new number to the selected load combination, which must be specified in a separate dialog box. This CO number must be unassigned.
Deletes the selected load combination.
The list only shows the load cases that are not yet contained in the load combination.
Selects all load cases in the list.
Inverts selection of load cases.