Load groups
Load groups
Use Load groups tool to set up load groups for calculations or for setting up automatic load combination generation.
When you select the Load groups tool, a new dialogue window opens.
On the left hand side, you can see a list of load cases and groups.
On the right hand side you can can change the settings for the selected load group or load case.
On the bottom part of the window you have three buttons:
- Add group - add a new load group
- Add subgroup - add a new sub-group to the selected load group. Read more about subgroups below
- Add case - add a new load case
Changes made in the Load groups dialogue do not save until you press the OK button in the bottom of the page.
Import/Export
When you click on the Import/Export button in the bottom, a new menu opens.
- Save as default - save the load groups, cases and their settings as a default for all future projects
- Save - save the load groups, cases and their settings with a name to use later
- Load - load previously saved load groups, cases and their settings
To read about the Load case settings see the topic
User interface ➔ Tab menus ➔ Loads ➔ Panel Load case, combination, group & construction stage ➔ Load cases
Grouping
In the list on the left hand side, you can set up the load cases and assign them to load groups.
There can be different type of load groups: Permanent, Stress, Temporary, Accidental and Seismic. There are also ungrouped load cases under the Independent load cases.
You can change the load group to different type if you select it and change its settings on the right hand side panel.
Loads can be moved from one group to another by dragging and dropping or using right-click menu or shortcut keys.
If you select the Load groups main category or Independent load cases, then you can see information about the shortcuts on the right hand side panel.
You can easily ungroup all or any load case by using the Insert load cases command on the Independent load case group.
Settings for each group type
There are specific settings for each load group type (Permanent, Stress, Temporary, Accidental and Seismic). These settings can be accessed if you select a group from the list.
There are also five types of settings that are the same for any group: Name, Type, Consider in max. of load group calculation, Load cases' relationship and Combination method. You can read more about these settings below.
Independent load cases
In Independent load cases type you can see and modify a list of load cases that are not assigned to any load group. Initially all load cases are here until they are assigned to groups. Load cases can later be unassigned from groups and they will appear in this list again. There are no settings for this Independent load cases type.
Load cases listed under this type are not used in load group analysis or in combination generation.
Permanent
Standard combinations
- Favourable - partial combination factor for favourable actions in standard combinations
- Unfavorable - partial combination factor for unfavourable actions in standard combinations
- ξ - reduction factor for unfavourable permanent actions in standard combinations
Accidental combinations
- Favourable - partial combination factor for favourable actions in accidental combinations
- Unfavorable - partial combination factor for unfavourable actions in accidental combinations
Stress
- Standard - partial combination factor for stress actions in standard combinations
- Accidental - partial combination factor for stress actions in accidental combinations
Temporary
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Safety factor - partial combination factor for variable actions
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ψ0 - factor for combination value of a variable action
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ψ1 - factor for frequent value of a variable action
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ψ2 - factor for quasi-permanent value of a variable action
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> arrow button - use the arrow button to select the factors from a predefined list of values that are based on the selected Eurocode. This will open a dialogue window, where you can select the suitable load category or type to automatically fill in all the factors
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Potentially leading load cases - select if the group contains possible leading load cases for load combination generation
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Ignore in SLS combinations - ignore the load cases in this group when generating SLS load combinations
Type of temporary effect
Some national annexes needs to know if the load is a wind or snow load.
- General - this load group does not contain any wind or snow loads
- Wind - this load group is considered as a group of wind loads
- Snow - this load group is considered as a group of snow load
Accidental
- Safety factor - partial combination factor for accidental actions
Temporary group highlighting in EN 1990 (6.11b)
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Using ψ1 - use ψ1 for any or all load cases in this group
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Using ψ2 (No highlighting) - use the ψ2 for any or all loads in this group
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Snow effect - if checked then a snow load that is considered as accidental load (in some national annexes) can’t be combined with a temporary snow loads
Seismic
- Safety factor - partial combination factor for seismic actions
Calculate maximum of...
- Seismic calculation results - automatically selects the results of seismic calculations
- User defined load cases - allow manually adding load cases to the seismic load group
General settings for every load group type
There are three types of general settings for any group type: Name, Type, Consider in max. of load group calculation.
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Name - change the name of the load group
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Type - change the type of the load group
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Consider in max. of load group calculation - include the selected load group in the Maximum of load groups calculations
Load cases' relationship
Use load cases' relationship radio buttons to select how the load cases in one group will be applied when generating the load combinations for analysis.
- Alternative - load cases will be applied mutually exclusively, so only one load case from the selected group will be active in one load combination. Number of possible load combinations is n
- Simultaneous - different load cases will be applied simultaneously, so one, multiple and all load cases from the selected group can be active in one load combination. Number of possible load combinations is 2^n
- Entire - all load cases are applied together from the selected group. Number of possible load combinations is 1
- Custom - user defined custom relationship between load cases in the selected group. Mainly used for complex models
Custom load case relationship
Use the Custom setting to define custom relationship between load cases in the selected group.
When you select the Custom relationship and press the Setup button, a new dialogue window opens.
Here you can see and modify a list of relationships between all the load cases in the selected group.
- Name - add a name to the relationship. You can create a new relationship by typing name into an empty row. You can delete a relationship by deleting the name on any row using the DELETE key on the keyboard
- Direction - some loads must be defined to act in certain directions. Select suitable direction:
- Non-directional
- X +
- X -
- Y +
- Y -
- ψ override - this field is only available for the Temporary load group. Use the override field to select different factors for each relationship. Return to the Default value by using DELETE key on the keyboard in the relevant field. Read below for more detail
- list of load cases in the group - after the Direction column (or ψ override column for Temporary load group), you can see a separate column for each load case in the current load group. Here you can select the magnitude of any load case in one relationship. 1.00 means 100% of the load case is acting during that relationship
- Add alternative - use the button to automatically fill in the relationships as if it used the Alternative relationship. That means load cases will be applied mutually exclusively, so only one load case from the selected group will be active in one load combination. Number of possible load combinations is n
- Add simultaneous - use the button to automatically fill in the relationships as if it used the Simultaneous relationship. That means different load cases will be applied simultaneously, so one, multiple and all load cases from the selected group can be active in one load combination. Number of possible load combinations is 2^n
- Clear - use this button to clear all the custom relationships. Deletes both the automatically generated and user added relations
You can add alternative, simultaneous and manual relationships at the same time. You can manually delete the relations that are not relevant.
ψ override
Use the ψ override field to select different factors for each relationship.
When you click in the ψ override field (whether it has already modified values or still as Default), a new dialogue window opens.
In the top, you can manually set new values for ψ0, ψ1 and ψ2.
In the middle you can select a substitute table from Eurocode using the drop-down box. The substitute list is shown in the bottom half of the dialogue.
In the substitute list, you can select one of the predefined set of factors based on the Description field by double-clicking on it.
You cannot apply the new factors just by highlighting the Description in the list. You must double click on it to really use it. Make sure that after the double click, the ψ values in the top change accordingly.
Combination method
This is a general group-independent setting for selecting which combination method will be used for generation of the load combinations from the load groups.
EN 1990 6.4.3 (6.10) and EN1990 6.4.3. (6.10a,b) are combinations according to the relevant Eurocode formula.
Use the Custom setting for manually defining the combination generation method. Read below for more detail.
You can hover over the options to see the formulas for both Eurocode combination methods.
Custom combinations
Use the Custom combination method to generate custom load combinations.
When you select the Custom method and press the Setup button, a new dialogue window opens.
Here you can see and modify a list of combination method between all the load cases in the load groups.
- Name - add a name to the combination. You can create a new combination by typing name into an empty row. You can delete a combination by deleting the name on any row using the DELETE key on the keyboard
- Type - change the type of the load combination. There are six different load combination types:
- U - ultimate limit state
- Ua - accidental ultimate limit state
- Us - seismic ultimate limit state
- Sc - characteristic serviceability limit state
- Sf - frequent serviceability limit state
- Sq - quasi-permanent serviceability limit state
- list of load groups - after the Type column, you can see a two or three columns for each load group: Status, Indicator and combination factor for each load group. Read more about the combination factor column below.
- Status - change the status of the load group for load combination generation. There are three statuses:
- M - mandatory. The load combinations according to the current rule (row of the table) are created with the defined factor of this load group.
- O - optional. The load combinations according to the current rule are generated both with 0.0 and the specified combination factor of this load group.
- D - deactivated. The load combinations according to the current rule are generated with 0.0 as the combination factor.
- Indicator - only for temporary load groups. There are three indicators:
- General - this option has no particular effect on load combinations.
- Highlighted - If the status of this load group is O (optional) and the load combination is generated with a factor of 0.0, then all the other temporary load groups that are set as Simultaneous will only be generated with a factor of 0.0, regardless of their settings. In all other cases, the load combination is generated for the Highlighted and Simultaneous load groups according to their statuses and factors. Cells of this type are highlighted in yellow.
- Simultaneous - the load combination generation of these load groups is partially controlled by the Highlighted load group.
- Add combination - use the button to automatically fill in the combinations from a list of predefined combinations. Possible options include: EN1990 6.10, EN1990 6.10 a, b, EN1990 6.11, EN1990 6.12, EN1990 6.14, EN1990 6.15, EN1990 6.16, EKS 6.10 b, b, EN1990 EQU, EN1990 6.10 A1.2(C), EN1990 6.10 a, b - Finnish NA, EN1990 6.10 a,b - Danish NA and EN1990 A2 - Infrequent.
- Clear - use this button to clear all the combinations. Deletes both the automatically generated and user added combinations.
Combination factor column
The combination factor column, which is marked with load group name, is for combination factor of that load group. You can either enter a numeric value or use one of the predefined symbolic representations.
If you select one of the symbolic representations, then the relevant combination factors and safety factors specified for that load group in the load group main dialogue are used. The predefined options include the following:
- for permanent load groups: Factorless, γ G_Sup, γ G_Inf, ξ * γ G_Sup, γ G_Sup Accidental and γ G_Inf Accidental
- for stress load groups: Factorless, γ P and γ P Acc
- for temporary load groups: Factorless, γ Q, ψ 0, ψ 1, ψ 2, γ Q * ψ 0, γ Q * ψ 1 and γ Q * ψ 2
- for fire load groups: Factorless and γ A
- for seismic load groups: Factorless and γ S
The Factorless representation will ignore the combination and safety factor for that load group and set the factor to 1.
If you enter a numeric value, then that value is used instead of the data in the load group main dialogue.
Subgroups
You can add subgroups to load groups to more easily control the load cases that are active in each load combination.
To add new subgroup, first select a load group from the list and then click Add subgroup button. A new subgroup is added and selected automatically.
On the right hand side, you can now see settings for the new subgroup:
- Name - name for the subgroup
- Master - you can select another subgroup to act as a master for the current subgroup. Read more about the master-slave subgroup logic below.
You can just drag and drop a load case into the subgroup or use the right-click menu or the buttons to add a new load case to the selected subgroup.
The load cases in one subgroup will always be applied with alternative load cases' relationship, but the subgroups themselves are applied as the selected relationship for current load group.
For example, if load group has load case relationship set to Entire and it has three subgroups with 5 load cases each, then load combinations will always take exactly one load case from every the subgroup, thus each combination has 3 load cases from this group.
Master-slave subgroups
Master-slave subgroup logic helps to synchronize the load cases so they are taken as proper pairs to the load combination. To set up the proper pairs, you first need to fulfill the requirements for one subgroup to act as a master and then select that master for another subgroup. Master can be only selected from subgroups within the same load group. Master and slave subgroups always have the same number of load cases in them.
Master subgroup
To set up the master subgroup, you have to add unique Position identifiers for each load case in that subgroup. Identifiers can be both letters and numbers. You can set the Position identifier on the right hand side after you have selected a load case in that subgroup:
In the picture above, the load case "LC-3" in the "SG-1" subgroup has already a Position identifier "a1" and the currenly selected load case "LC-4" is beieng defined as "a2". You can see that the third load case "LC-5" in this subgroup "SG-1" is without the Position identifier at the moment and thus this subgroup cannot be used as a master.
Slave subgroup
To set up the slave subgroup, you first must have a master subgroup within the current load group. Then you can set the current subgroup as a slave by selecting a suitable master subgroup from the Master dropdown list on the right hand side:
Synchronizing the load cases between master and slave
When you have set one subgroup as a slave to another, the the load cases within both subgroups will be synchronized. This function depends on how the slave subgroup was prepared before the master was selected. There are two options:
- automatic load case generation - if the current subgroup is empty, then setting the subgroup as slave will automatically generate new load cases with proper Position identifiers into this subgroup. If the current subgroup already has load cases, then all load cases with matching Position identifiers will be used, all load cases without matching Position identifiers will be moved to Independent load cases group and missing Position identifiers will be generated as new load cases. Now all load cases in the current subgroup will be synchronized to the master subgroup.
- manual load case generation - if you manually added load cases to the current subgroup and manually set matching Position identifiers for all the cases in the current subgroup, so that the Position identifiers now exactly match the needed master subgroup, then setting the current subgroup as slave will synchronize all load cases in the current subgroup to the master subgroup.
When the load cases are synchronized, then only load cases with same Position identifier from each master-slave subgroup will be selected together for load combinations and no load combination will have mixed load cases from these master-slave subgroups.
You can see that the load cases are synchronized if they are blue and the subgroup has a word "Slave" in the parentheses.
In the image above, you can see that the subgroup "SG-2" is a slave to the subgroup "SG-1". All three load cases in both subgroups are synchronized. When generating load combinations from these load groups, then following three load case pairs will be used together:
- "LC-3 [a1]" and "Dead load case [a1]"
- "LC-4 [a2]" and "SG-2-a2 [a3]"
- "LC-5 [a3]" and "LC-6 [a3]"