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Frequently Asked Questions (FAQ)
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AnswerSimilarly to surfaces, there are various smoothing options for displaying the results of support reactions. For a nonlinear support, you should always select the actual distribution to display the results.
You can find the setting in Window 1.5 Support.
Here, you can enter the support width and type, and specify whether to carry out the moment redistribution, or the reduction of moments or shear forces.
Depending on the standard selected in Window 1.1, there are different options available. The option applies to RF‑CONCRETE Members (RFEM 5) and CONCRETE (RSTAB 8).
The definition of surface supports should be as close to reality as possible. Experience shows that the equation solver works most efficiently in this way. For simplification reasons, degrees of freedom are often defined as "fixed." However, this may have a great impact on the overall stiffness matrix and cause numerical problems (see Figure 01).
To avoid the numerical problems, it is better to work with springs. It is often sufficient to define very stiff springs (see Figure 02). The same applies to the foundation perpendicular to the surface. You can find more information in  and under the links below this FAQ.
To do this, select the checkbox in Column J in Window 1.2 Geometry (see Figure 01).Then, it is possible to view the release definitions in the "Releases" tab (see Figure 02).If you want to modify the releases, you have to set the "User-Defined" support type in the "Support" tab. Then, you can freely define the releases (see Figure 03).
AnswerWhen importing support reactions as loads from another RFEM file, it is possible to select the type of load distribution. In this case, the "Uniform" and "Polygonal" options are available.
In the "Edit Nodal Supports" dialog box, it is possible to rotate the local axis system of the support (Figure 01). First, select the sequence that controls the sequence of the local support axes X ', Y', and Z', and then specify the rotation angle about the global axes X, Y, and Z in the corresponding text boxes.
The support rotation can also be determined graphically by using the corresponding buttons in the dialog box. The rotation of the support is displayed dynamically in the dialog graphic.
After the calculation, the support reactions of the rotated nodal support can be evaluated both on the global axis system and the local axis system (Figure 02).
AnswerThe default definition of surface elements assumes the isotropic material behavior. The load attempts to get to the supports as quickly as possible. The stiffness of the elements also plays a role here.
In the case of plates, the best way to display and represent the structural behavior or the load transfer is to use the trajectories of the principal moments αb. For wall elements, it is necessary to consider the trajectories of the principal axial forces αm.
In this example, the load is not transferred parallelly to the free edges of the plate, but almost perpendicularly to the supports as this is the shortest path of the load transfer.
At the dulled corners of the structure, the load application area is larger than in the support centers, corresponds to a singularity point, and as a consequence of that, it has great peak values.
In order to force the system to remove the load parallel to free plate edges, the following procedure is the fastest:
Definition of an orthotropic plate. It is recommended to use the "Effective Thicknesses" orthotropy type. The effective plate thickness has to be specified in the support direction and a very small thickness in the secondary support direction (for example, 1 mm).
The second figure shows the difference between both models.
AnswerTo be able to consider this nonlinearity, you can use the "Partial activity" function (see Figure 01). In this way, you can define the limit moment, from which any other moments will be taken into account.
For surface supports, this option is only available if there is also the nonlinearity defined in the local z direction (failure if contact stress in z is negative/positive). In the dialog box where you can edit the nonlinearity, you can find the "Friction in plane xy" option.
This option works as shown in the graphic dialog box: The support in the x and y direction is fully accepted only when reaching the contact stress Tau (contact stress Sigma multiplied by the friction coefficient). It is necessary to reduce this linearly in advance.
In order to use this option, a support must be in the horizontal directions. It can be defined as fixed or with an elastic spring. If the spring is defined with 0, no support is considered even though a friction coefficient has been entered.
AnswerAccording to the default setting in the program, it is defined that the loads act on all surfaces.However, if there is no surface available in the file, the load cannot act and a warning will be displayed. If you click "OK" to confirm the message, the load will be imported into the model anyhow, but not applied to any surface. However, as soon as you define a surface , the imported loads can act on it.
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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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