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• ### For the settlement calculation with the RF-SOILIN add-on module, the weight gamma and the specific gravity gamma, sat are interrogated for a certain soil. What do I need the value gamma, sat for, and how does it fit into the calculation?

New FAQ 003422 EN

The value $\gamma,_{sat}$ corresponds to the weight of the saturated soil and can be adjusted, if necessary, in the material parameter settings. If there is groundwater in a layer, the weight of the saturated soil $\gamma,_{sat}$ is automatically reduced from this layer by the weight of groundwater (10kN/m³). Above this layer, the stresses are calculated with the specific weight of the soil.
• ### How can I change the Standard / National Annex set for the design in add-on modules?

New FAQ 003312 EN

You can usually set the standard and the National Annex in the top right corner of an add‑on module (see Figure 01). In most cases, it is also possible to display the factors of the National Annex and edit them, if necessary (see Figure 02).
• ### Is it possible to prevent RF-SOILIN from recalculating the foundation any time load changes are carried out in the governing load case in a simple manner?

FAQ 003212 EN

No, that is not possible. The calculation of the foundation parameters in RF-SOILIN is performed iteratively. For the first iteration step, it is necessary that the start values for the foundation parameters are selected internally by the program. With these start values, you can perform a finite element analysis of the FE model in RFEM.

The result is a distribution of the soil pressure. The soil pressure of the first iteration step is included as an initial value in the RF-SOILIN calculation. Together with the stiffness modulus of the entered soil layers, it is possible to calculate the settlement for each finite element. The settlement and soil pressure are then used to calculate the foundation parameters.

In the next iteration step, the new foundation parameters replace the old one and a new finite element analysis is started, which in turn yields a new distribution of overloading pressure. As a convergence criterion, we compare the new distribution of soil pressure with the old one.

As long as the deviation exceeds a certain convergence limit, the new distribution of soil pressure in RF-SOILIN is considered in the calculation of new foundation parameters. When the deviation of the distribution of the soil pressure of two consecutive iteration steps is not reached for the first time, the iteration is ended and the foundation parameters of the last iteration step are output as the result in RF-SOILIN.

• ### Can I also calculate foundation bodies at different foundation depths in a model with RF-SOILIN?

FAQ 003207 EN

Yes, that is possible. There is an option to enter additional geological regions (see Figure 1). In Window 1.2, you have to select the "Additional geological regions" check box. Then, you can define the shape, coordinates, and number of layers of the additional geological region in window 1.3. In this way, different founding heights of several floor slabs can be displayed correctly in the model.

• ### Why do I receive such high contact stresses at the foundation edges of my floor slab?

FAQ 003199 EN

Depending on how rigid a foundation body is, the distribution of overloading pressure under this structural component changes as well. In case of non-prestressed foundation bodies that are loaded by a uniform surface load, it is generally assumed that the overloading pressure distribution is a mirror image of the load. The plate forms a subsidence basin. However, the more rigid the plate becomes, the more the contact stress rises towards the edge (theoretically limitless).

• ### How can I specify different subgrade moduli for a large floor slab?

FAQ 003148 EN

The definition of surface supports (foundation) in RFEM is a property of the surface.

This means that you have to divide the entire floor slab - depending on the areas with different subgrade moduli - into several surface components.

• ### I am getting red values displayed in the intermediate results of RF-SOILIN. What is it all about?

FAQ 003132 EN

In case of the result values are displayed in red, it refers to an error message.
The defined thickness z is then not sufficient. The standard specifies that the thickness must be calculated up to the value where sigma_Z is ≦ 0.2* sigma_ü. In the graphic, 0.2 * sigma_ü is displayed as a gray line, sigma_Z as red.

The layer structure should have such a thickness that both lines intersect.
In Figure 1, the two lines do not intersect, so that the values are displayed in red and a sufficient thickness must be defined.

• ### Currently, I have the problem that the calculation in RF-SOILIN takes extremely long and does not converge. What can I do?

FAQ 003051 EN

Often, these problems can be solved easily and effectively.

Especially in the edge areas of plates, the results often oscillate. In this case, the result can be improved by modeling a foundation overlap with a negligible thickness around the surface. It is assigned the same foundation as the main plate. The foundation overlap shows the edge area of the plate more accurately and the convergence behavior is often better.

It is important to obey the rule that the foundation overlap must be extended at least so far that the basin is completely subsided.
Thus, it is also possible to represent graphically the influence of settlement on surrounding buildings.

• ### When calculating with RF-SOILIN, I receive the error number 10739 with the message "The structure is above the terrain". What should I do?

FAQ 002936 EN

The reason for the error message is the different heights of the floor slabs.
Figure 1 shows that the program has several levels of soil layer
generated to the soil layer between the individual soil samples. Due to the different
Heights of the floor slabs would theoretically cause some surfaces to hang in the air (thus the error message is displayed).

There is a function in RF-SOILIN that can describe additional geological regions (see Figure 2 and Figure 3).

• ### Does the calculation in RF-SOILIN work with solids as well?

FAQ 002935 EN

Yes, the calculation also works with volume cores. Important for the calculation is only that the solid must be embedded with one surface side (base plate). This means that a storage of the volume body is only possible with linear bearings for the calculation by means of RF-SOILIN.

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