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Frequently Asked Questions (FAQ)
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AnswerFor volumes, we do not provide any internal forces in the program. The conversion of the Spannnugnen in internal forces would be very complex, since not only mx, my and mz would be present, but also the parts of the drill, mxy, myz, mxz also lateral forces and normal forces. With volume one limits oneself usually on a direct voltage evaluation. If you still need internal forces, you have the option to apply the internal forces of the volume to a rod. For this purpose the result bar was implemented in the program.
AnswerPlease double check if you have released the correct elements and the correct amount of elements. If you have only 2 beams connected to each other, please make sure you have released only one of them.
AnswerThis depends on the choice of model type. In this case a flat system was chosen. Thus, only for this level, the relevant results are displayed because they are reduced because of the limited coordinates and degrees of freedom. If, on the other hand, a 3D system is selected as the model type, all stresses and internal forces are displayed.
AnswerThe area on the right in Fig. 1 therefore receives a moment in the area of the support because this surface is rigidly connected to the support (the surface itself does not have a line joint). If one wants to exclude this moment, one would therefore have to create an additional line joint for the right-hand surface or provide the support with a rod end joint.
AnswerIn RSTAB there is also the possibility to determine plastic internal forces. To do this, one must select a plastic joint as non-linearity via the rod properties (see Figure 1). However, this does not involve interaction of the plastic forces. Another possibility is to directly set joints with nonlinear properties. However, with this method you have to estimate in advance where these joints form.In RFEM it is possible to select a corresponding material model (see Figure 2).
The following points should be considered to ensure that the determined internal forces can be used for the design:
The model should represent the real structure as exactly as possible. For this, materials, surface thicknesses, cross-section dimensions, hinge definitions, support conditions, etc. must be defined correctly.
The loads must be defined and applied according to standards. The combinatorics can be imported automatically by RFEM.
When considering internal forces from result combinations, care must be taken to evaluate the correct max / min values. The maximum compressive force in a column corresponds to the minimum axial force (min N).
In RF- / STEEL Warping Torsion, the imperfection is applied in both directions (+/-). Thus, the + imperfection can be governing at one x-location, while the - imperfection is governing at the adjacent x-location. The governing result is displayed in the result tables and the graphic in the graphic. This could be the cause of the described effect.
Please check the boundary conditions, that is, the definition of the nodal supports, and in particular the application of the imperfection in window 1.13 "Parameters - Sets of members". The imperfection is preset as L / 150, which may represent a conservative solution.
The easiest way to find the internal forces at these nodes is to print the pictures of members into the printout report.
If this solution is not an option, you can also find the values in the result table 4.1 in the printout report. Since the extreme values are only activated by default, it is still necessary to activate nodal values in the selection.
It is usually not reasonable to include the internal forces of all member in the printout report. Therefore, you can only select the members that are relevant to you.
AnswerIn such a case, one should first look at the distortions. It is often the case that the bars at the junctions were not properly connected (minimal inaccuracies). Due to the unrealistic large resulting twists around the rod axis then arise these moments.
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