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• When trying to create an FE mesh, I get an error message. I cannot find any mistake. Something seems to be wrong with the surface axes.

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Perhaps the input parameter for the surface is missing. In the model file of the FAQ, the axis of the surface refers to a line that has obviously been deleted before. Thus, it is not clear how to create the axis system for the surface.

There are two simple solutions:

1. Select a line to which the x- or y-axis should be parallel.

2. Switch back to the default setting.
• I have modeled two nodes on a surface in RFEM. The results do not show the displacement at these two nodes. How can I obtain it?

After creating the two nodes, for which you want to display the displacement, you should ensure that they belong to the surface.

If these two nodes are not connected to a line, it is necessary to integrate them in the mesh to be considered in the calculation with finite elements.

To integrate these objects that are not used in the mesh, click the Calculate menu → FE Mesh Settings, which opens the FE Mesh dialog box. In this dialog box, select the Integrate unutilized objects into surfaces check box.

After the calculation, you can see the displacement of these nodes in Table 4.2 Nodes - Displacements.

• After activating a layered FE mesh, the axis orientation is automatically reset to the default. How can I keep the defined axes after layering the FE mesh?

When using a layered FE mesh for solids, it is unfortunately not possible to keep the user-defined axis orientation because the layers are always in the z‑direction, and thus the axis definition is determined automatically.

As an alternative, you can use an FE mesh refinement, see the figure.

• Is it possible to also have RFEM output the area of each finite element along with its location?

There is no option for viewing the FE mesh nodes in RFEM along with those areas but it is possible to export them to an Excel sheet. You can do this by following the steps in Figure 01.

In Figure 02 the coordinates of the FE mesh nodes are exported to Excel.

Also, exporting the FE mesh as a .dxf file into AutoCAD can be done. Using the direct export option in RFEM, select the FE Mesh option. See this in Figure 03.

Another option is to go to File - Export and then select the following format.

Then, under the Geometry tab, check off the boxes below.

• How can I modify the FE mesh settings via the COM interface?

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The general FE mesh settings can be modified using the IFeMeshSettings interface. This interface is located under IModel > IModelData > ICalculation. Figure 01 shows which elements can be modified / displayed.

Here is a code example where the target length of the FE elements is set to 100 mm. Furthermore, the division of the members with the same element size is activated and the minimum division is set to 3 elements:

Sub mesh_params()Dim iApp As RFEM5.Application'   get interface for model dataDim iModel As RFEM5.modelSet iModel = GetObject(, "RFEM5.Model")On Error GoTo eIf Not iModel Is Nothing Then        '   get interface for application and lock licence    Set iApp = iModel.GetApplication()    iApp.LockLicense        '   get interface for model dat    Dim iModdata As RFEM5.IModelData2    Set iModdata = iModel.GetModelData        '   get interface for calculation    Dim iCalc As RFEM5.ICalculation2    Set iCalc = iModel.GetCalculation()        '   get interface for mesh settings    Dim iMeshSet As RFEM5.IFeMeshSettings    Set iMeshSet = iCalc.GetFeMeshSettings        '   get general mesh settings    Dim meshGen As RFEM5.FeMeshGeneralSettings    meshGen = iMeshSet.GetGeneral        meshGen.ElementLength = 0.1        '   set new general mesh settings    iModdata.PrepareModification    iMeshSet.SetGeneral meshGen    iModdata.FinishModification        '   get mesh member settings    Dim meshMem As RFEM5.FeMeshMembersSettings    meshMem = iMeshSet.GetMembers        meshMem.DivideStraightMembers = True    meshMem.ElementLength = 0.1    meshMem.MinStraightMemberDivisions = 3        '   set new mesh member settings    iModdata.PrepareModification    iMeshSet.SetMembers meshMem    iModdata.FinishModification            iApp.UnlockLicenseEnd Ife:  If Err.Number <> 0 Then    MsgBox Err.description, , Err.Source    End If    iApp.UnlockLicense    Set iApp = Nothing    Set iModel = NothingEnd Sub

The subroutine is also completed by an error interceptio routine (On Error GoTo e) and the Prepare-/FinishModification block is required as in the case of modifying other elements. Here, the block is created via the IFeMeshSettings interface.

• When I create a user-defined result value, the RFEM solver window opens briefly and the calculation is apparently performed again. Why? I have already performed the calculation before.

If you have performed a calculation in RF‑CONCRETE Surfaces, the results are available on FE mesh nodes and on grid points.

If you set a user-defined result value in a surface, an interpolated value from the existing values from the calculation in RF‑CONCRETE Surfaces is displayed on the FE mesh nodes first. This interpolated value is displayed while the user-defined result value is being set (when moving the mouse pointer over the surface).

If closing the command to set the user-defined result value (ESC key), RF‑CONCRETE Surfaces recalculates this actual value at this location. As a consequence, the solver window is displayed briefly. Depending on the complexity of the calculation, this solver window is only displayed for a short time or several seconds.

Due to the initial display of the interpolated values and the subsequent calculation of the actual result value, there may be small differences.

• My RFEM file includes some RWIND Simulation load cases. After deleting the FE mesh, these load cases are no longer available. However, these load cases are still available in the automatically generated combinations and I get an error message when starting the calculation. What can I do?

If you want to consider the load cases again, please perform a new RWIND Simulation calculation. If you want to perform the calculation of the existing combinations, please remove the RWIND Simulation load cases from the Wind action before deleting the FE mesh, then the combinations are created again and it is possible to perform the calculation.
• Is it possible to export the results from RF‑CONCRETE Surfaces to Excel? For example, I would need the steel stress of serviceability design.

Yes, the results can be partially exported. The export function is available for the result tables in the add-on module (as of Window 2.1).

Using the example of the steel stress in SLS, it would be possible to only perform the steel stress analysis and then export the table in Window 3.3, for example.

When displaying the table in Window 3.3, you can choose between FE mesh points and grid points. The grid can be adjusted as a property of the surface.
• How can I define the exact location in the case of a message saying that distorted FE elements have been found? These areas cannot be detected at first glance.

If the distorted elements are so small that they cannot be detected (see Figure 01), it is recommended to "Display Mesh Quality Annotations." You can find this option in the Display navigator → FE Mesh → FE Mesh Quality. There, you can activate the annotations for the "Warning" and "Failure" elements (see Figure 02). Thus, you can immediately recognize where the location is by using the values. For larger models, it may be helpful to hide the model during the search.
• When generating the FE mesh of an ETFE cushion, some problems occur. I cannot find any mistake. What can I do?

In most cases, the problem is that the finite elements of the cover surfaces are very close to each other in the edge area of the cushion when using Bézier surfaces. The FE mesh nodes of the bottom and top surface might be combined then. In principle, there are two approaches:

1. Numerical solution of the problem:

You can adjust the tolerance for combining FE mesh nodes by using the menu "Tools" → "Regenerate model."

2. Geometrical solution of the problem:

A more workable solution is to increase the distance between surfaces by using the boundary surfaces as shown in Figure 01.

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First steps

We provide information and tips to help you get started with the basic program RFEM and RSTAB.

Wind Simulation & Wind Load Generation

With the stand -alone program RWIND Simulation, you can simulate wind flows around simple or complex structures 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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