#### Further Information

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• ### What happens if I activate the "Soil failure" function in RF-SOILIN?

The zero coefficient of structural soil strength can be used for better convergence of deeper excavations or small loading. Damaged soil have no structural soil strength. Therefore, it better picture damaged subsoil in the upper layers with this function. The possible entry for the depth of the soil failure is from 0.0 m to 1.0 m.
• ### 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?

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?

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 there a way how to easily prevent RF‑SOILIN from recalculating the foundation every time the load in the governing load case is changed?

No, that is not possible. The calculation of the foundation parameters in RF‑SOILIN is performed iteratively. The first iteration step requires that the start values for the foundation parameters are selected internally by the program. These start values can be used to perform a finite element analysis of the FE model in RFEM.

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

In the next iteration step, the new foundation parameters replace the old ones, and a new finite element analysis is started, which results in a new distribution of soil contact stress. As a convergence criterion, the new distribution of soil contact stress is compared with the old one.

As long as the deviation exceeds a certain convergence limit, the new distribution of soil contact stress in RF‑SOILIN is considered in the calculation of the new foundation parameters. In the case the the deviation of the soil contact stress distribution 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 given as a result in RF‑SOILIN.

• ### Can I also use RF‑SOILIN to calculate foundation bodies at different foundation heights in a model?

Yes, it is possible. For this, there is the option to enter additional geological regions (see Figure 01). In Window 1.2, you can 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, it is possible to model different foundation heights of several floor slabs correctly in the model.
• ### Why do I obtain such high contact stresses at the foundation edges of my floor slab?

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

These theoretically infinite stresses cannot of course be absorbed by the soil. The soil would probably deflect laterally at the edge and the stress would migrate inwards from the edge.
• ### How can I specify different moduli of subgrade reaction for a large floor slab?

FAQ 003148 EN

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

Figure 01 - Dialog Box "Edit Surface" with Definition of Support

This means that you have to divide the entire floor slab into several sub-surfaces, depending on the areas with different moduli of subgrade reaction.

• ### In the intermediate results of RF‑SOILIN, there are red values displayed. What is it all about?

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

The layer structure should have such a depth that both lines intersect each other.
In Figure 01, the two lines do not intersect, so the values are displayed in red, and it is necessary to define the sufficient depth.
• ### Currently, I have the problem that the calculation in RF-SOILIN takes extremely long time and does not converge. What can I do?

These problems can often be solved easily and efficiently.

Especially in the edge areas of plates, it is common that the results oscillate. In this case, the result can be improved by modeling a foundation overlap with negligible thickness around the surface. The same foundation is assigned to this 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 extend the foundation overlap at least so far that the basin is completely subsided. Thus, it is also possible to graphically display the influence of the settlement on the 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?

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).

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#### First Steps

We provide hints and tips to help you get started with the main programs RFEM and RSTAB.

#### Wind Simulation & Wind Load Generation

With the stand-alone program RWIND Simulation, wind flows around simple or complex structures can be simulated by means of a digital wind tunnel.

The generated wind loads acting on these objects can be imported to RFEM or RSTAB.

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