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Frequently Asked Questions (FAQ)
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AnswerThe default definition of surface elements assumes the isotropic material behavior. The load attempts to get to the supports as quickly as possible. The stiffness of the elements also plays a role here.
In the case of plates, the best way to display and represent the structural behavior or the load transfer is to use the trajectories of the principal moments αb. For wall elements, it is necessary to consider the trajectories of the principal axial forces αm.
In this example, the load is not transferred parallelly to the free edges of the plate, but almost perpendicularly to the supports as this is the shortest path of the load transfer.
At the dulled corners of the structure, the load application area is larger than in the support centers, corresponds to a singularity point, and as a consequence of that, it has great peak values.
In order to force the system to remove the load parallel to free plate edges, the following procedure is the fastest:
Definition of an orthotropic plate. It is recommended to use the "Effective Thicknesses" orthotropy type. The effective plate thickness has to be specified in the support direction and a very small thickness in the secondary support direction (for example, 1 mm).
The second figure shows the difference between both models.
AnswerPlease reduce the maximum distance between the node and the line in the FE mesh settings. Even with a setting of 0.001 m according to the figure, you can enter a smaller value. If the decimal places are adjusted by means of the corresponding settings, the value is also displayed completely.
You can find the corresponding setting in Program Options in the 'Program' tab (see the figure): unselect the 'Combination description according to action category' option in order to display load case numbers for LCs.
Depending on the selected type of load determination, RF‑PUNCH Pro determines the punching load from shear forces in the control perimeter. For this, the internal forces in surfaces from the RFEM model apply.
If the FE mesh in the area of the punching node is not dense enough, this can lead to inaccurate results. In this case, you will get the message No. 56 in Window 2.1.
To avoid this problem, you should carry out the FE mesh refinement in the area of the node of punching shear in the RFEM model. You can arrange this either directly on the node or on the adjacent lines of wall ends or wall corners.
If you create sufficiently dense FE mesh refinement, the warning message disappears automatically after a recalculation in RF‑PUNCH Pro.
The program interprets the entered model for the calculation in a FE mesh. This mesh depends on the shape parameters set in the 'FE Mesh' dialog box.
In order to correct any inaccuracies in the model, there is the parameter ε in the FE mesh settings. In the figurative sense, it regulates the maximum distance between the FE nodes. If the distance between the elements / nodes in the model is smaller than the parameter ε, the FE nodes are merged. The result of this merging is then the described 'connection' of the members in the calculation.
You can avoid this effect and simulate the members independently by setting the parameter ε smaller than the available distance.
For the stability design of compression elements, you need the combination of RF‑CONCRETE Members and RF‑CONCRETE NL. The reason is the following:
First, the internal forces of the individual load combinations (second-order analysis + imperfection) are subjected to the linear-elastic calculation. For this, you basically only need RFEM.
Then, the cross-section design is performed in RF-CONCRETE Members with these internal forces determined linearly-elastically, and the required bending reinforcement is determined from these internal forces.
This bending reinforcement is then compared with the user-defined entries concerning the existing basic reinforcement or the minimum reinforcement and based on this, the reinforcement concept is generated (dialog box '3.1 Existing Longitudinal Reinforcement' of the module).
This existing longitudinal reinforcement is then used for the nonlinear design.
According to Section 5.8.6 (1), geometric nonlinearities must be taken into account according to the second-order analysis. However, the general rules for nonlinear methods according to 5.7 also apply.
In Sec. 5.7(1), 'an adequate non-linear behaviour for materials is assumed'. According to 5.7(4)P, the use of material characteristics which represent the stiffness in a realistic way but take account of the uncertainties of failure shall be used when using non-linear analysis.
This requires the RF-CONCRETE NL add-on module. Thus, the geometric and material nonlinearities are considered and the requirements of EC 2 regarding the ultimate limit state design are fulfilled.
Similarly, this method is also available in RSTAB in the CONCRETE add-on module.
Yes, you can. It is possible to export the critical perimeter from RF‑PUNCH Pro as a line to the RFEM model. This is possible for all punching forms (supports, wall ends and wall corners). The corresponding button can be found in the result window 2.1 'Punching Shear Design' (see the figure).
In the RFEM model, you will then get a line, where you can create a 'section' for further analyses, for example. Please note that the line must be integrated into the FE mesh of the surface. The setting for this can be found in the general FE mesh settings.
Unfortunately, there is no 'Split surface along selected line' feature. You can either split the surface equally or along all the integrated lines.
In order to split the surface on one integrated line only, it is necessary to temporarily manage the integrated lines manually (see Figure 01). After splitting the surface, you can enable the automatic object detection again (see Figure 02).
AnswerYou find this setting in the "General Data" of the model.You can distinguish between the model types "3D", "2D - XY", "2D - XZ" and "2D - XY".If you want to enter a floor as a 2D model, and the axial forces within the slab should not be taken into account, set the model type to "2D - XY". If you want to enter a wall, set "2D - XZ".Find more information in the RFEM manual, chapter 12.2.1 General - Type of Model.
AnswerThe title block of the printout report is created using the authorization file, which was used in the initial installation of our programs.
A subsequent change in the authorization file does not necessarily change all report headers immediately.
For the changed title block to be created as default in the authorization file, the "old" one has to be removed first.
To do so, please delete the file "DlubalProtocolConfigNew.cfg" in the following (default) directory:
While deleting the file, our applications must be closed!
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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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