The initial state of the soil is analyzed and determined in RFEM 6 by means of a load case that contains the loads acting prior to the construction (for example, only the soil self-weight under gravitation). In the following text, the entries for creating and using the initial state will be shown and explained.
Definition of the load case that should be the initial state
For permanent loads from the soil self-weight, the "Permanent/Soil" action category is available in the Geotechnical Analysis add-on. If this category is selected in a load case, the self-weight that can be activated only affects the weight of the soil solids of the entire model. With such a load case, the primary stress state can be determined. The setting of the "Permanent/Soil" action category and the resulting restriction of the self-weight on soil solids can be seen in the following image.
Option A - Manual specification in the load combination
For all other load cases and load combinations, this load case can be used as the initial state. Thus, at the beginning of the actual analysis, each node of the structure has the stresses and strains from the initial state. The setting for the initial state in the load combination dialog box is shown and highlighted in color in the image below.
Option B - Automated data entry using the combination wizard
If a combination wizard is used for generating load combinations, the initial state can be set in the combination wizard and thus entered into the load combinations during the generation.
The following figure shows the input dialog box for the combination wizard and the setting for the initial state.
The initial state entered by the combination wizard can be edited without problems after the generation.
Type of Initial State
In RFEM 6, different types of initial states are available. Open the setting for the type of load case to be used by clicking the icon to the right of the selection, as shown in the image below. Within the geotechnical analysis, the "Final State" type should be used to determine the initial state. It includes all stresses and strains for the structure resulting from the selected load case.
Further information about the existing types can be found in the manual for the main program.
Resetting deformations
The nodal displacements of the initial state can be reset before a further FE calculation. For example, this is required to consider the primary stress state.