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Frequently Asked Questions (FAQ)
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The first natural frequency is required to determine the structure coefficient. It is not determined by using a generalized formula, but the integrated eigenvalue solver RF‑/DYNAM, taking into account the real mass distribution and displaying the results in Column A of Table 2.3.
Beam steering is the angular rotation of antennas under the effect of the present loads (wind, overload, earthquake, deformation, and so on). As an indication, for the GSM, the value of the beam steering must not exceed 1°. This limit of beam steering is often accessible in the clauses of the Technical Specifications of the project.
In RF‑/TOWER Design, it is possible to control the beam steering of antennas for the SLS design. To activate this rotation design of antennas, go to Details → Serviceability.
Figure 01 - Option for Rotation Design of Antennas
As soon as you select this check box, the antennas are available in Window 1.10.2 Serviceability of Antennas. Here, you can enter the angular rotation limit of each antenna.
Figure 02 - Window 1.10.2 - Serviceability of Antennas
After the calculation, the maximum ratio is displayed in Window 2.7 Design by Antenna.
Figure 03 - Window 2.7 Design by Antenna
A user-defined wind load distribution is not provided in the Eurocode. In order to implement a user-defined wind load distribution in the RF‑/TOWER Loading add-on module, this can only be done after conversion to DIN, for example, DIN 4131:1993‑11, see Figure 01, Window "1.3 Wind Load - Part 1."
Then, you can select the user-defined distribution in Window 1.4 "Wind Load - Part 2," and define it in the adjacent table, see Figure 02.
AnswerThe programs RFEM or RSTAB is very well suited to perform these designs . Add-on modules for steel or solid construction support your individual solution approaches.
Special add-on modules from the RF-/MAST series extend and simplify the possibilities.
Main Programs RFEM or RSTABUsing the main programs, the structures and materials, and the effects can be defined.With RSTAB, you can edit and calculate truss-like or frame-like structures. RFEM enables also the processing of plates, panes, shells, and solid elements.
Add-on modulesRF-/TOWER Structure
helps in the efficient generation of three- or four-sided tower structures
includes a comprehensive library with add-on parts and allows for a quick and easy integration into your model.
supports you professionally in the generation of wind, ice and traffic loads.
RF-/TOWER Effective Lengths
determines the effective lengths of members especially for masts
does the design according to EN 1993-1-1, EN 1993-3-1 and EN 50341 incl. NA.
RF-/JOINTS Steel Tower
designs hinged bolt connections of lattice towers according to EN 1993-1-8
Wind analysis in a digital wind tunnelUse RWIND Simulation for advanced flow behavior analyses. The results can be used directly as loads or load cases in RFEM or RSTAB.
Dynamic AnalysisIf earthquake calculations or vibration tests are necessary, the RF-/DYNAM Pro add-on modules provide suitable tools for determining natural frequencies and shapes, for analyzing forced vibrations, for generating equivalent loads or for non-linear time history analysis.In case of having any further questions about the Dlubal software, contact the sales department, please.
Yes, it is; the RWIND Simulation program is designed universally and can implement any model of RFEM or RSTAB.
Figure 03 - RFEM Model
For a steel structure consisting of pure member elements, the program creates a coherent, voluminous envelope of member surfaces for the numerical wind tunnel. The result of this modeling for the simulation depends on the available cross-sections and the mesh settings. Due to the wind flow, the corresponding surface pressures result on this surface layer.
Figure 02 - Surface Pressure on OpenFOAM Mesh
After the wind flow analysis, the program summarizes the surface pressures of the member units, and gives back the corresponding equivalent load (single, uniform, or trapezoidal) for each member axis.
Figure 04 - Options for Member Load Distribution
These loads are applied in RFEM or RSTAB for the further calculation of internal forces.
Figure 05 - Equivalent Load from RWIND Simulation
The "Simulate and Generate Wind Loads" interface application allows you to exchange member, surface, and solid elements in RFEM, and member elements in RSTAB.
To avoid too fine mesh and thus too long calculation time, the program simulates all members with a rectangular cross-section by default. In this case, the size of the rectangular cross-section is selected in such a way that it barely includes the real cross-section geometry.
By deactivating the "Export optimized member topology" option, you can avoid this additional optimization of the model and allow consideration of the real cross-section geometry within the existing cross-section settings.
If the exact display of the cross-section geometry requires more than 1,000,000 elements, the interface automatically switches to the simplified rectangular cross-section display.
AnswerIn the RWIND Simulation program, a stationary flow analysis of incompressible gases is implemented. The principles and formulations used for this do not change over time. Thus, the calculation gives a result set without temporal variation. The effect of a "Kármán vortex street," in which counter-rotating vortices develop behind a body around which flows, results in a temporal change of the flow effect. Therefore, this fluid-mechanical effect cannot be simulated in RWIND Simulation.
AnswerBy using the FE mesh refinement, the program allows you to create a mapped FE mesh. The automatic FE mesh generator can thus be controlled to a certain extent. However, a specified mesh geometry cannot be set.
If the flanges are not continuous and the diagonals are fastened to the flanges, it may be necessary to enter an intermediate member.
Figure 1 shows a structural system where the flange is not continuous, but the diagonals are rigidly connected to the flange. To transfer the moments of the diagonals to the flange, the diagonal must get to the flange before the joint, otherwise the moment of the diagonal will be transferred to the opposite member (see Figure 02).
In the case the diagonals are also connected by hinges, you can waive the intermediate member. Please note that at least one member will not be hinged in order to prevent the connection node to rotate freely (see Figure 03).
If using a vertical, this must be connected on one of the two flanges or be between both flanges. In both cases, the model from Figure 1 arises, and has to be modified accordingly. Figure 04 shows the model with the vertical between the flanges and Figure 05 shows the model with the vertical on the right flange.
AnswerIn the result tables of the add-on module, you can find all intermediate values for each wind direction, face and sector. This feature is also available in the long version of the printout report, though it can significantly increase the size of the report.
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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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