Load Cases

Loads from a specific action are stored in a load case (LC). Load cases are, for example, self-weight, snow, or imposed load.

List

The "List" manages all the load cases of the model. The Buttons for "List" of Object Types table describes the functions that you can use to create, copy, or delete objects of a list.

No. and Load Case Name

The number of the new load case is preset. Use the Table input in the RFEM workspace if you want to leave gaps in the numbering for later additions.

Enter a load case name, or select an entry from the list that briefly describes the load case.

To Solve

The check box controls whether the load case is analyzed in the calculation. This way, you can exclude load cases from the calculation that do not occur in isolation, such as wind, without considering the self-weight.

Main

The Main tab manages the general specifications of the load case selected in the "List" to the left.

Categories

If you have not activated any add-ons in the model's Base Data, only the "Static Analysis" is available in the "Analysis type" list.

In the "Static analysis settings" list, you can select the calculation theory according to which the load case is to be analyzed. The following analysis types are available:

• Geometrically linear
• Second-order (P-Δ)
• Large deformations

The analysis types are described in the Static Analysis Settings chapter. Use the button to add a new analysis type.

Self-Weight

If you want to consider the self-weight of the model as a load in the load case, select the "Active self-weight" option. Use the "Factor in direction" fields to define the effective direction of the self-weight. The default setting is factor 1.00 in direction Z, or -1 if the global Z-axis is pointing upwards.

RFEM determines the self-weight from the material and object properties. If you apply the automatic self-weight in several load cases, you should consider this when combining the load cases.

Action Category

The standards mention different action categories that control the superposition of load cases, as well as the partial safety factors and combination coefficients.

You have to assign a category to each load case. You can do this using the list. The categories are linked to the standard you defined in the "Base" tab.

The "None" action category represents a special case: It allows you to create a load case without assigning a category; for example, to apply imperfections by means of user-defined equivalent loads (stabilizing loads). Load cases of this type are not considered in the action combinations.

Options

If you tick the "Consider imperfection" check box, you can select an imperfection case (see the Imperfection Cases chapter) in the list, or use the button to create a new one. In this way, an imperfection is applied in the load case at the same time.

Example: in the "Wind in X" load case, the imperfection case named "Imperfection in X" is considered. Thus, imperfections in X are applied for all load combinations with wind in the X-direction, but not imperfections acting in other directions.

The "Structure modification" check box allows you to consider a stiffness adjustment or a special treatment of nonlinearities in the load case. These functions are described in the Structure Modifications chapter. Select the structural modification in the list, or create a new modification type with the button.

Special Options

If you activate the "Consider initial state from" check box, you can select a load case from the list whose deformations represent the initial position for the selected load case. This way, you can determine the effect of prestress, for example.

The button to the right of the list opens the "Initial State Settings" dialog box. Define the "Type of Initial State" that is available.

The possibilities have the following meaning:

• Final State: The model state is memorized as it is available after the calculation of the specified load case, and is used as the initial state for the calculation of the current load case. This is suitable, for example, for construction phases, form-finding processes, or geotechnical analyses.
• Stiffness: The stiffnesses of the model objects are adopted as they are available after the calculation of the specified load case. Both the geometric stiffness (an object subjected to compression is less stiff under bending than an object subjected to tension) and the physical stiffness due to nonlinearities (failed members are missing in the matrix) are taken into account.
• Strains: The Strains of the structural objects, which are available in the specified load case, are adopted. Thus, the model is only deformed; no forces are generated. When the "Strains with user-defined factors" option is set, you can scale the strains in an object-related way in the "Individual Factors of Selected Objects" table below.