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Loads

Last modified by Akos Rechtorisz on 2023/03/20 15:28

Contents

Filter loads by value

From now on, it is possible to filter and select loads based on their value using the Filter tool (Quick tools).

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Psi factors for subgroups of Load groups

In FEM-Design, traffic loads used by bridge engineers must be represented by a temporary load group containing all the load models as load cases (or as subgroups, if moving loads are considered). The different actions are created by custom relations between sub-elements of the load group, where each relation is considered as a traffic load action (group of loads, e.g. “gr11” for railway bridges). The following figure shows an example of defining a two-track railway traffic load.

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According to EN 1990 A2, for combinations of actions (ULS or SLS), each traffic load action may have a different simultaneous factor (Psi factor). In order to accommodate that in the program, a new column is introduced in the Load cases’ relationship dialog for temporary load groups in FEM-Design 22, where one can override the original load group Psi values for each relationship.

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An empty cell in the Psi values column means that the original Psi values of the load group will be used in the combinations / GMAX calculations.

New values can be added by selecting the cell and clicking on it with the left mouse button. A new window opens, where the Psi values can be set by entering them in the corresponding edit fields. Table A2.1, A2.2 or A2.3 can be seen from EN 1990 with the appropriate selection in the combo box. One can automatically fill in the edit fields by double-clicking on the appropriate row in the table. After clicking OK, the new Psi values will appear in the table cell with the format {Psi0, Psi1, Psi2}.

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Comment

  • Pressing the Delete key on the keyboard clears the selected cell (meaning the original Psi values are used). Deleting a cell in other columns will delete the entire row.
  • Copy-paste works for the “Psi values” column.

Improved Load groups combinations

The generation of load combinations and the calculation of the maximum of load groups are generally based on the regulations of EN 1990:2011. However, there are cases where one wants to set a different relation of load groups (e.g. Finnish and Danish National Annex, EKS11 in Sweden, EQU or STR/GEO A1.2 (C) combinations, etc.). For this purpose, a new so-called Custom settings of Combination method has been introduced inside the Load groups tool in FEM-Design 22.

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Clicking the Setup button displays a tabular interface (Load group combinations) for entering the combination rules. A rule is represented by a row that can be automatically generated by selecting a standard regulation from the list displayed by clicking the Add Combinations > button. All data can be deleted by clicking the Clear button.

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The meaning of the individual elements of the table:

The first two columns:

  • Name: The name of each row must be unique. The contents of the cell do not affect the calculation.
  • Limit state: Each rule must be assigned to one of the six different limit states (e.g. Accidental). The choice is available through the combo box.

Then, each load group is represented by two or three columns:

  • S (Status): This column appears for all load group types and has three possible values:
    • “Mandatory”: The load combinations according to the current rule (row of the table) are created with the defined factor of this load group.
    • “Optional”: The load combinations according to the current rule are generated both with 0.0 and the specified factor of this load group.
    • “Deactivated”: Load combinations according to the current rule are generated with 0.0. All cells belonging to deactivated load groups are highlighted in gray.
       
  • I (Indicator): This column is only displayed for temporary load group types. Each cell has three valid options (can be selected via a combo box):
    • General: This option has no particular effect on load combinations.
    • Highlighted: If the status of this type of load group is “Optional” and the load combination is generated with a factor of 0.0, all other temporary load groups that are set  Simultaneous (see below) 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 status (see explanations above). 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 (see explanation above).

Finally, the name of a group: In this column, there are two options to set the load group factor:

  • Select the symbolic representation of the factor from a combined field (e.g. “Gamma_G_Sup” for permanent load groups). Thus, the factors for load combinations are calculated from the actual settings of the load group (e.g. “Gamma_G_Sup” is set and the unfavorable factor for normal combinations is 1.35, then this load group is calculated with a factor of 1.35).
  • Enter a numeric character string (e.g. 0.5). This load group is represented by this number in the load combinations, regardless of the settings in the main load group dialog.

     

Restrictions

  • The seismic group must always be “Deactivated”, except for the seismic limit state, where it must be mandatory.
  • The accidental limit states must contain at least one non-deactivated accidental group.
  • Accidental load groups can only be active in accidental limit states.
  • ULS and SLS combinations must contain at least one non-deactivated permanent, stress or temporary load group.
  • For permanent and stress load groups, the symbolic factors “Gamma_G_Sup_Accidental”, “Gamma_G_Inf_Accidental” and “Gamma_P_Accidental” are valid only in accidental limit states.
  • The indicator (“I” column) of a “Deactivated” temporary load group cannot be " Highlighted”.
  • A row can contain maximum one highlighted load group.
  • Names must be unique.
  • Temporary load groups that cannot have leading load cases (setting in the load group dialog) cannot be highlighted.
  • Temporary load groups ignored in SLS combinations (setting in the load group dialog) must be deactivated in SLS load group combinations.
  • The load group dialog cannot be closed with the OK button if the Custom option is selected with an empty table.
  • When adding a new group or changing the type of an existing group, the column corresponding to the group will be filled with “Deactivated”, “General”, “Factorless”, unless both the group and the limit state are seismic: then the cells will be "Mandatory" and "Gamma_S".

     

Comment

  • Copy/Paste (Ctrl+C, Ctrl+V) works for the table. Validity of the pasted data is checked when the OK button is clicked.