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Frequently Asked Questions (FAQ)
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In RFEM, the interface application 'Simulate and Generate Wind Loads' makes it possible to exchange member, surface, and solid elements, and in RSTAB to exchange the bar elements.
To avoid generating a too fine mesh along with a corresponding long calculation time, the program simulates all members with a rectangular cross-section as standard. The size of the rectangular cross-section is selected in such a way that the real cross-section geometry is barely included.
By deactivating the option 'Export Optimized Member Topology', you can avoid this additional optimization of the model and allow consideration of the real cross-section geometry within existing cross-section settings.
If the exact representation of the cross-section geometry requires more than 1000000 elements, the interface automatically changes to the simplified rectangular section display of the cross-sections.
AnswerTo enter a taper on a beam, it is necessary to select the Layout dialog section. A taper can be modeled either on the bottom side or on the top side of the beam.The plate thicknesses, as well as the height of the taper, are defined by selecting a tapered cross-section, since, for example, repeatedly cut rolled cross-sections are used. If any plates are used, a parametric T-profile can be selected. The length of the taper, as well as the material, are entered in the same dialog section. The weld thicknesses for connecting the taper to the beam can be defined in the Welds dialog section.If a tapered member is already used as a beam (entered in the 'Nodes and Members via Different Cross-Sections and Lengths' section), it is not possible to model an additional taper.
AnswerWith the FE mesh refinement, it is also possible to create an aligned FE mesh in the program. Thus, the automatic FE mesh generator can be controlled to a certain extent. However, it is not possible to use it for setting of a specified mesh geometry.
AnswerIn addition to geometry input errors, this discrepancy is usually caused by a different calculation basis of both add-on modules.The design of an end plate joint with the RF‑/JOINTS Steel - DSTV add-on module is carried out by comparing the saved ultimate limit states with the design internal forces. The underlying resistances are taken from the current DSTV guidelines.When using the RF‑/JOINTS Steel - Rigid add-on module, the joint resistances of are calculated according to DIN EN 1993‑1‑8 by means of the component method. Thus, you can directly affect the results via the settings you have made.In this case, an elastic distribution of bolt forces is used as a basis by default. By selecting the plastic force distribution in the joint, you can activate additional load capacities. These are already included in the ultimate limit states according to the DSTV guidelines.In order to obtain the comparable results between both add-on modules, it is necessary to apply the plastic force distribution for the calculation. Furthermore, you should pay attention to the correct modeling of the joint geometry.
AnswerIn the case of significant deviations, the problem may be caused by the applied bending theory (Mindlin or Kirchhoff).For this, see FAQ Mindlin Kirchhof.
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.
AnswerYes, 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.
Yes, that is possible. The "Generate Loads → From Surface Load to Openings" function allows you to do just that (see Figure 1). For the load, you can select in which direction the load should act, the area load distribution, the area load direction, the load distribution type, and of course the surface load (see Figure 2).
Thus, it is possible to set the loads e.g. for non-load bearing elements such as windows or the like.
AnswerThis message is usually displayed in the case that the member dimensions do not correspond.In the example model, the beam has a flange width of 200 mm and the column support of 160 mm.This joint is not valid in the add-on module as the flange width of the column should be at least as large as the flange width of the structural element to be connected. As soon as the cross-sections are defined according to this rule, the connection design can also be performed.
AnswerIf 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.
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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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