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Frequently Asked Questions (FAQ)
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AnswerIn RF-/JOINTS Steel - Rigid, the design according to EN 1993-1-8 Chapter 6.2.7 Equation 6.24 is implemented. If the acting axial force exceeds 5% of the plastic resistance N pl, Rd , Equation 6.24 is used.
AnswerThe design of a rigid connection of this type without a web stiffener or an end plate is only possible with the RF-JOINTS Rigid add-on module. Find an example in the download section
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.
AnswerThe RF-/JOINTS add-on module is divided into several joint groups. For this, see the following FAQ.Therefore, there is no straightforward answer to the special aspects of the design as in this FAQ.In contrast to the RF‑/TIMBER Pro add-on module described in the mentioned FAQ, however, it is obvious that the RF‑/JOINTS add-on modules cannot design EC2, even if manually changing the LDC, for example in the RF‑/JOINTS Timber - Steel to Timber add-on module (see Figure 01).Furthermore, this also applies to the add‑on modules RF‑GLASS and RF‑/CONCRETE NL.The reason for this is that there are stiffnesses exported in the program in the case of some joint groups of the RF‑/JOINTS add‑on module. For nonlinear calculations, the superposition with result combinations is not allowed. In the case of the second result combination mentioned above, there is the special feature that the superposition is no longer conservative, even in the case of simple structures. The design cannot be also performed correctly by manually changing the LDC.Nevertheless, if a result combination should be superimposed with constant and alternative additive, it is necessary to split EC2 in the attached file into load combinations as follows.
- RC2*=CO1 or CO2
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.
The geometry depends on the definition of the structural components. In the "1.2 Nodes and Members" window, you determine, which member belongs to a column and which to a beam. In the default case, the program always recognizes the column as continuous structural component (see Figure 01). In order to make the beam continuous, you simply have to change the status of the individual members (see Figure 02). The given beam will be assigned the “Column” status and the given column will be defined as a “Beam”.
Designs in our module RF-/JOINTS Steel - Rigid are based on the assumptions and regulations of the standard EN 1993‑1‑8. Here, bending from the main beam plane is not considered.
In RFEM, it is possible to model any rigid joint. All internal forces can then be taken into account.
RF-JOINTS performs an idealized design of a steel connection according to the standard, which cannot be easily compared with an exact FE calculation.
Thus, the following conditions must be met:
- Consideration or exclusion of friction/compression/tension within the contact solid (tab 'Solid') as well as for the bolts modelled subsequently
- Consideration of internal forces and deformations within the subsequently modelled end plates or similar, which causes redistribution of bolt forces in the FE calculation (in contrast to the idealized design in RF‑JOINTS)
This can be corrected by rigid connection objects, for example (an end plate as a rigid surface).
- Uniform load introduction into the FE model, for example, by using rigid members or rigid surfaces as described in the article 'FEM Modeling Approaches of Rigid Connections'
In the RF‑/JOINTS add-on module, you can export result graphics as DXF files. The corresponding button is below the graphic in Window 4.1 (see Figure 01).
After you click the button, the Windows dialog box 'Save as' appears where you can enter the name and the file path of the DXF file.
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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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