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Frequently Asked Questions (FAQ)
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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.
AnswerThe internal forces and deformations are determined according to the second-order analysis for flexural-torsional buckling taking into account 7 degrees of freedom. For a linear calculation of deformations, a vertical/horizontal load results in only one vertical/horizontal deformation. Since the internal forces refer to the deformed system and it is a nonlinear analysis, this is not valid for the second-order analysis for flexural-torsional buckling.
The deformations in the shear center can be checked in RSTAB and RFEM with the RF-/FE-LTB add-on module (see Figure 02). The deformations that additionally result from the displacements or rotations can only be controlled with a surface model in RFEM.
AnswerFrom the formula apparatus of EC 3-1-8, it is clear that the limit tensile forces of the cross-section's end plate are introduced into the column flange and thus directly into the column web.
Therefore, the upper end plate is not fully stressed by these forces.
For purely structural reasons, the column top plate is available for the stiffening and the panel boundary and serves for the transmission of the proportional force flowing into the stiffener in case of a required diagonal stiffener.
You can control the detail categories in the input dialog box "1.3 Cross-Section" and in the "Edit Claim Types" dialog box.The specified standard values can be selected here. It is not possible to manually adjust these values.
AnswerIn CRANEWAY the internal forces are typically displayed only for max and min locations. If you want to get each internal force on each x-location, then you have to run the detailed calculation and to disable the option "Show only governing results". How to do it, we show you in the short video.
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.
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.
AnswerSince the equivalent member designs of Eurocode 3 have different interactions than are the case for the designs according to the partial internal forces method and a mixture of these different designs is not desired for reasons of clarity, RFEM deactivates the equivalent member designs when using the RF-/STEEL Plasticity add-on.
AnswerThe analysis of a rigid column footing is performed according to EN 1993-1-8 in the RF-/JOINTS Steel - Column Base add-on module. The standard only provides for simple bending in the design format. The design can be performed for compression only, tension, simple bending, or a combination of bending and tension, or bending and compression. If the note is confirmed with 'Yes', the add-on module performs all designs neglecting the unsupported internal force Mz.
The term "shear panel" indicates that the translational spring, which is created along the beam length by means of the shear panel type including the corresponding parameters, is smoothed, see Figure 1.
This is also the case for the shear panel type "Bracing", so that the mode shape always appears to be arbitrary at this location, see Figure 2.
In order to obtain accurate results, it is recommended to manually define a lateral support by means of a nodal support according to the general method (Figure 3) or to define the effective lengths according to the equivalent member method, including intermediate restraints, if necessary. Finally, a eigenvector with visible lateral restraint in the mid-span is created (Figure 4).
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