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Frequently Asked Questions (FAQ)
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RF-/STEEL Cold-Formed Sections is a module extension of RF‑/STEEL EC3. The only thing you need to do is to activate the design for cold-formed cross-sections in the detailed settings of RF‑/STEEL EC3 (Figure 01).
Common cold-formed cross-sections can be modeled in SHAPE‑THIN. In General Data, select the "c/t parts and effective cross-section properties" check box (Figure 01).
Then, select the "EN 1993‑1‑3 (Cold formed cross-section)" option in the "c/t-Parts and Effective Cross-Section" tab of the Calculation Parameters dialog box (Figure 02).
You can optionally check the geometric conditions for the applicability of the standard specified in EN 1993‑1‑3 , 5.2. To do this, select the corresponding check boxes. If the geometric conditions are not met, an error message appears before the calculation.
First, enter the elements of the cross-section. The notional flat widths are usually generated automatically from the geometry conditions, but can also be created as user-defined in Table "1.7 Notional Flat Widths | EN 1993‑1‑3" (Figure 03) or in the corresponding dialog box.
Then, you can define stiffeners in Table "1.8 Stiffeners" or in the corresponding dialog box (Figure 04).
Furthermore, you should specify the buckling panel in Table "1.9 Buckling panels" (Figure 05) or in the dialog box. To do this, select the elements of the buckling panel. The stiffeners located in the stiffened panel are identified automatically.
For the design of a cold-formed cross-section in RF‑/STEEL Cold‑Formed Sections, it is sufficient to define the stiffeners and panels of the cross-section. It is not necessary to additionally calculate the effective cross-section in SHAPE‑THIN. Thus, you can start the calculation and click "OK" to confirm the warning message (Figure 06).
After saving the calculated cross-section, it can be imported into RFEM or RSTAB.
AnswerWith the PLATE-BUCKLING add-on module, you can only calculate rectangular buckling panels.The panel is entered via 1.1 of the add-on module. Alternatively, the panel can also be created from an existing RFEM or RSTAB file by selecting the respective c/t-part.
An overpressed joint between two members can be controlled in RFEM by means of the member stress results. For members, this stress result represents the effective stress as a color gradient across the member surface depending on the assigned cross-section.
Figure 01 - Stresses on Members
Based on the local member axis, the member stress result gives the following stress components and reference stresses with an associated color palette:
- Elastic stress component
- Elastic equivalent stresses
Using active displaying for the members connected to the joint, and displaying the σx stresses, it is possible to visualize the state of stress on and thus also between the members. If only negative stresses occur in the area between the members, the joint is overpressed.
AnswerThe zero coefficient of structural soil strength can be used for better convergence of deeper excavations or small loading. Damaged soil have no structural soil strength. Therefore, it better picture damaged subsoil in the upper layers with this function. The possible entry for the depth of the soil failure is from 0.0 m to 1.0 m.
AnswerSo that smooth ranges are taken into account in the design in RF-STEEL surfaces, they must always be activated in the detail settings of the add-on module. See Figure 01 with the detail settings in RF-STEEL Surfaces.
AnswerYou will find an option in the "Settings" of the add-on module (see picture 01).
Only the default setting of 1 load increment can be set when a complex nonlinear material model is defined. The reason for this is because the program cannot determine the correct material stiffness for each incremental loading amount. The exact maximum load needs to be applied to the structure in order to determine the state of the material's stress/strain diagram.Figure 01 - Material Model - Nonlinear material definedThis setting can be found and changed under "Calculation Parameters" as well as under the "Calculation Parameters" in the load cases and combinations dialog box.
AnswerIn the RF-/STEEL add-on module, an equivalent stress design is performed according to von Mises. An elastic stress design (EL-EL) is to be made. In RF-/STEEL EC3, a classification is carried out before the design. If the cross-section is classified as class 1 or class 2, the design is performed against plastic limit internal forces. An EL-PL design is performed. If you do not want to use the plastic load reserves, you can switch the design to EL-EL in the details of the RF-/STEEL EC3 add-on module. The results are then comparable with RF-/STEEL.
Most likely, the error is in the selection of the cross section:
For a steel design, a thin-walled flat steel cross-section should be selected instead of a rectangular solid cross-section, see Figure 1.
The reason for the high shear stress of a solid cross-section is caused by the existing stress points of the cross-section or by the corresponding thickness of this stress point.
In the case of a thin-walled flat steel cross-section, there are four stress points at the corner points of the cross-section with the corresponding thickness t = 10 mm, see Figure 2.
For a solid cross-section, however, there is another stress point in the center, where the maximum of height h or width b is assumed as the thickness t for this cross-section type. In this case, the width b is 200 mm, see Figure 3.
This results in a small torsional section modulus Wt and a correspondingly high shear stress.
Therefore, the solution is, as described above, to select flat steel within the main program.
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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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