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Frequently Asked Questions (FAQ)
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Answer
Stiffeners may only contain elements with a thickness t> 0 mm. If you select null elements (thickness t = 0 mm), the message shown in Figure 1 is displayed. The null elements have to be replaced by elements with a thickness t> 0 mm.
Figure 01 - Error message "At least one of the selected elements is of type Null"
The stiffener shown in Figure 2 includes elements 8 and 3. However, element 3 has a thickness t = 0 mm, so that the message in Figure 1 is displayed. For element 3, define a thickness t> 0 mm. Alternatively, you can delete element 3 and connect element 8 directly to the buckling panel. This is also shown in the video.
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Answer
If the stiffeners in the buckling panel are not explicitly defined as stiffeners, the message shown in Figure 01 is displayed.
The stiffeners are defined in Table "1.8 Stiffeners" or in the "New Stiffener" dialog box (Figure 02). Specify the elements that belong to the stiffener. In the case of angles, trapezoidal stiffeners, etc., the buckling stiffness is represented by several elements. If the stiffener represents a cross-section from the cross-section library, it must first be broken down into its elements.
Figure 02 - Input of support elements in dialog box and table
The buckling panel shown in Figure 03 contains elements 1 to 3. The elements 8, 9 and 10, 11 are connected to the buckling panel. However, these are not defined as stiffeners so that the message shown in Figure 01 is displayed. The elements 8, 9 and 10, 11 must be defined as stiffeners in Table "1.8 Stiffeners" or in the "New Stiffener" dialog box (Figure 04).
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Answer
Elements that stiffen a buckling panel at the edges do not represent buckling stiffeners in the sense of a stiffened overall panel according to EN 1993-1-5 [1] , Section 4.5. If the limits of the buckling panel are defined as buckling stiffeners, the message shown in Figure 1 is displayed. These stiffeners must be deleted.
Figure 01 - Error message "The stiffeners cannot be at the end of the buckling panel"
The buckling panel shown in Figure 2 includes elements 1 - 3 and stiffeners 1 - 4. However, stiffeners 3 and 4 are located on the edge of the buckling panel (marked in red in Figure 3), so that the message shown in Figure 1 is displayed. These stiffeners must be deleted (Figure 4). This is also shown in the video.
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Answer
The buckling panel must be supported at its start and end, that is, provided with a support. If this is not the case, the message shown in Figure 01 appears.
Figure 01 - Error message "The c/t boundary area is not supported."
If there is a free edge, add the support manually. The support can be specified in columns "C" and "D" in Table "1.7 Cross-Section Parts for Classification According to EN 1993-1" or in the "Edit c/t-Part" dialog box (Figure 02).
Figure 02 - Support in dialog box and table (marked in red)
The buckling panel shown in Figure 03 contains elements 1 to 3. However, the elements have no support at their free ends (marked red in Figure 04), so the error message shown in Figure 01 is displayed. The support must be supplemented (Figure 05) so that a calculation is possible. This is also shown in the video.
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Answer
The type of stiffener (Figure 1) selected in the "Support" tab of Table "1.2 Geometry" has an effect on the buckling analysis of the beam, as this results in the contribution of the web χW to the shear resistance according to EN 1993-1-5 [1] , 5.3 is influenced.
Figure 01 - Selection of support stiffener
The factor χW for the web contribution to the shear resistance is displayed in the result table for the buckling analysis (Figure 2).
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Answer
Even if the description of the add-on modules is very similar, the calculations performed are different.
RF-/STEEL
This add-on module performs a general stress analysis by calculating the existing stresses and comparing them with the limit stresses. The designs are performed elastically. The designs do not depend on a standard.
RF-STEEL EC3
This add-on module, on the other hand, performs all typical designs of ultimate limit state, stability, deformation, and fire resistance for steel members according to Eurocode 3 (numerous National Annexes are available). There is a range of module extensions available within this add-on module. These include: warping torsion analysis, plasticity analysis, designs for cold-formed sections.
Comparison of Both Add-on Modules
The results of RF‑/STEEL can be compared with the results of the cross-section design of RF‑/STEEL EC3.
Figure 01 - Comparison of Design Ratios in Both Add-on Modules
Why the results can differ is explained in FAQ 003489.
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Answer
The message shown in Figure 01 is displayed if you select the "Minimum distance between stiffeners: 30 ε t" check box in Details and the clear distance between the stiffeners is smaller than this minimum distance amin. The minimum distance is calculated as follows:
amin = 30 ⋅ ε ⋅ t
where
ε = √(235 / fy [N/mm²])fy is the yield strength,t is the thickness of the buckling panel.
In this case, the distance of the stiffeners must be increased in Window "1.2 Stiffeners." For the buckling panel shown in Figure 01, the clear distance between the stiffeners is:
Δz = z2 - z1 - (t1 + t2) / 2 = 890 - 600 - (10 + 10) / 2 = 280 mmThis distance is smaller than the minimum distance:
amin = 30 ⋅ ε ⋅ t = 30 ⋅ √(235 / 355) ⋅ 12 = 292.9 mmTherefore, the position of Stiffener 2 should be entered at least
z2 = z1 + (t1 + t2) / 2 + amin = 600 + (10 + 10) / 2 + 292.9 ≈ 903 mm
This distance is also displayed as information in Window "1.2 Stiffeners" when placing the mouse pointer over Stiffener 2 (Figure 02).
Figure 02 - Proposed Position of Stiffener
If the calculation should also be performed for a stiffener distance smaller than the minimum distance, the "Minimum distance between stiffeners: 30 ε t" check box must be deactivated (Figure 03).
Figure 03 - Deactivating Option "Minimum Distance Between Stiffeners"
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Answer
Yes, the data is freely available. You can download the presentations and finished models by the speakers under Downloads below. -
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The input of intermediate lateral restraints is used to enter lateral supports on a member without having to insert a node in the model at this location. Furthermore, the design of sets of members using the equivalent member method requires them to define the existing support conditions at the intermediate nodes of the set of members.
The entered intermediate lateral restraints are then considered as additional boundary conditions in the eigenvalue solver. However, some boundary conditions are already included in the input tables of the nodal supports or the effective lengths.
To avoid conflicts or duplicate entries for the same location, the error message "Invalid location of the intermediate lateral restraints" appears. The following locations are not allowed as they are already defined in the other entries:
Design of Members:
- Start and end of a memberDesign of Sets of Members:
- Start and end of all members if they are entered using nodal supports
- Start and end of a set of members for the design using the equivalent member methodFigure 01 - Incorrect Location of Intermediate Lateral Restraint for Equivalent Member Method
Figure 02 - Incorrect Entry of Intermediate Lateral Restraint for Input of Nodal Supports
However, it is very easy to find the error, because the first line with the wrong entry is automatically selected after confirming the error message.
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Answer
The fire resistance design with RF‑/CONCRETE Columns is performed according to the simplified calculation method according to EN 1992‑1‑2 [1], Section 4.2. The program uses the zone method described in Annex B.2:In case of exposure to fire, the bearing capacity is reduced due to a reduction of the component's cross-section and a decrease of material strengths. The concrete zones that are directly exposed to fire and thus damaged are not taken into account for the equivalent cross-section used for the fire resistance design. The fire protection design is performed with the reduced cross-section and the reduced material properties analogous to the ultimate limit state design at normal temperature.That is: The nominal curvature method according to [1], Section 5.8.8, is performed with the hot materials and reduced cross-section.
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First Steps
We provide hints and tips to help you get started with the main programs RFEM and RSTAB.
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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