In the Design Situations table of the 'Concrete Foundations' category, all design situations defined for the model are listed. For concrete foundations, two standards are relevant for assigning the design situation types:
- EN 1992 for concrete design
- EN 1997 for geotechnical design
The design situations are described in the Design Situations chapter of the RFEM manual.
The designs according to EN 1992 and EN 1997 are distributed among different design situations, depending on the limit state:
| Design Situation | Performed Designs |
|---|---|
| DS1 – ULS (STR/GEO), Eq. 6.10 | EN 1992 designs (bending, punching shear, shear resistance, minimum reinforcement, etc.) as well as bearing resistance and sliding according to EN 1997 |
| DS2 – SLS characteristic | Severe eccentric loading & foundation rotation (limitation of open joint) according to EN 1997 |
| DS3 – ULS (EQU) | Positional stability (equilibrium of the foundation body) according to EN 1997 |
Selecting Design Situations for Concrete Foundations
The 'To Design' check box is activated by default for all design situations. Thus, all design situations are examined in the concrete foundation designs. If you clear a check box, the corresponding design situation is deactivated for the concrete design, and no designs are performed for this design situation.
The settings in the table are synchronized with the specifications for the design situations in the 'Load Cases and Combinations' dialog.
Self-Weights for Concrete Foundations
In the 'Load Cases' tab of the 'Load Cases and Combinations' dialog, you can define for each load case whether and how the self-weight is to be considered for concrete foundations. To do this, select the Self-weights for concrete foundations option in the 'Self-Weight' section. The Concrete Foundations tab is added.
In the 'Concrete Foundations' tab, you can define whether the self-weight of the foundation structure, the earth covering, and the groundwater should be considered.
If earth covering and groundwater are activated and their properties have been defined in the Soil Properties dialog, the corresponding loads are generated automatically. If they are deactivated, you must define them manually as additional foundation loads, if necessary. An explanation of this can be found in the Earth Covering and Groundwater chapters.
To ensure that the self-weight is also combined with the partial safety factor of 1.0 in the ultimate limit state, activate the Favorable permanent actions check box in the 'Options II' section of the Combination Wizard.
Design Situation for the Sliding Safety
For the sliding design, the vertical load has a stabilizing effect (it generates friction in the base joint). A favorably acting load must not be factorized with ULS factors, because this would artificially increase the sliding resistance and thus provide an unsafe result. Therefore, the vertical force must be applied with its characteristic (unfactorized) value.
So that the add-on can determine this value, the corresponding characteristic action must be assigned to each ULS load combination:
When using the Load Combination Wizard, the corresponding load combinations are assigned automatically.
