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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 member 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-section 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, the cause is usually the different calculation principles of both 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 load capacities with the design internal forces. The underlying load capacities are taken from the current DSTV guidelines.When using the RF-/JOINTS Steel - Rigid add-on module, the capacities of the connections are calculated according to DIN EN 1993-1-8 by means of the component method. Thus the results can be directly influenced by the used settings.By default, an elastic distribution of bolt forces is used as a basis. By selecting a plastic force distribution in the connection, you can activate additional load capacities. They are already included in the limit load capacities according to the DSTV-guideline.Therefore, to obtain comparable results between both add-on modules, a plastic distribution of forces must be applied for the calculation. In addition, it is important to ensure a correct modeling of the connection geometry.
AnswerIn case of significant deviations, the problem may be caused by the applied bending theory (Mindlin or Kirchhoff).See also Mindlin Kirchhof FAQ
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.
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.
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.
AnswerIt is often the case that the member dimensions do not match.In the example model, the beam has a flange width of 200 mm and the column support of 160 mm.This joint is not allowed in the add-on module because 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 is also satisfactory.
AnswerIn 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.
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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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