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  • Answer

    In order to optimize or minimize all processes in general for larger models, attention should be paid to various points. It can be an advantage if

    • the wireframe model is used instead of the filled model in the graphic
    • the table and navigator displays are deactivated,
    • our programs are added to the exceptions in the settings of the antivirus program,
    • as few applications and RSTAB / RFEM files as possible are opened at the same time,
    • the PC is upgraded. For example, you can often achieve a significant increase in performance with SSD memory. The PC should also have sufficient random access memory.
    Furthermore, generated loads can negatively affect the performance as they are recalculated in the background after each work step. If there are very many in the model, it may sometimes be useful to separate them (see Figure 2). However, the enormous advantage that the loads are adjusted automatically when changes occur in the model is lost.

    It may also be advantageous to save the RSTAB / RFEM files locally instead of in a network.

    It may also be due to missing user rights if the program reacts slowly. If you are not working under an administrator account, the user must have full access rights to different directories and subdirectories.

    Furthermore, you should pay attention to always work with the current version of RSTAB / RFEM.

  • Answer

    When creating User-Defined Toolbars, always pay attention that no commands are moved to the standard toolbars and menus. These tables are always overwritten when installing the program for reasons of updating. The user-defined toolbars and menus are compatible and remain after an update.

    In the "Configuration Manager" dialog box, you can use the "Export Configuration as File" option to save the entire setting including all other objects (colors, options, borders, etc.).
  • Answer

    When components are calculated with the Finite Element Method (FEM), you can choose between surfaces and solids in RFEM. The big advantage of surfaces is the calculation time, because the FE elements are only defined in the surface plane. The third dimension, that is the thickness, is considered as a physical property in the calculation. Thus, a surface can be considered as a mathematical simplification. In addition, surfaces can be meshed more easily than solids (Jacobi Matrix).

    Plate elements are divided into two types of elements. Whereas in the classical thin plate theory (Kirchhoff) shear deformations due to shear forces are neglected, special extended approaches have to be assumed for the thick plate theory (Reissner-Mindlin). For thin plates, the pure bending reaction is dominant. Therefore, the simplified bending theory is also sufficient. As the thickness increases, the proportion of the transversal shear influence on the load bearing capacity increases. Starting at a certain thickness, the error due to neglecting this component is so large that it is absolutely necessary to have the higher theory of the thick plate. Considering a slab as being "thin" or "thick" does not depend on the ratio "dimension to thickness" of the single finite element, but on the conditions in the structural system. Influencing factors include, in addition to the plate thickness, especially the span lengths (length, width, radius), the type of support and the load type as well as their distribution. Due to the multitude of influences, it is not possible to specify a mandatory value.

    Figure 01 shows a guideline describing the validity of the corresponding elements. The size "d" is the thickness of the structural component and "L" the length of the structural component or the distance between the supports. The ratio d/L gives an indication of when an element is valid for an analysis. If d/L is large, the shear deformation is a critical parameter and the user should prefer to use solids. If d/L is small, the shear deformation has no decisive influence and surface elements are the most effective choice.

    Figure 02 performed calculations with the different elements. A top view is shown so that the deformations can be interpreted on the image plane. For a small d/L ratio of 0.2, the deformations very well match for all three variants. If d/L = 0.4, differences between the thin and thick plate calculations are already noticeable. In the extreme case d/L = 0.7, a difference of the thick plate to the solid is additionally observed. The loads have been selected in such a way that the same deformation is achieved for all solid elements to produce a meaningful printout.

  • Answer

    The definition of surface supports (foundation) in RFEM is a property of the surface.


    Figure 01 - Dialog Box "Edit Surface" with Definition of Support

    This means that you have to divide the entire floor slab - depending on the areas with different subgrade moduli - into several surface components.

  • Answer

    Unfortunately, the calculator implemented in Windows 10 is not compatible with our programs. You can use e.g. the “Copy” option to paste the values into the clipboard and then paste them into the program to still use the calculator. A better alternative is to replace the Windows 10 calculator with Windows 7 or Windows 8. There are sufficient instructions on the Internet to carry out this procedure. It is only necessary to make sure that the file calc.exe in the Windows folder C:\Windows\System32 starts the old calculator afterwards. The Windows 7 calculator can then be used as usual after importing the results.

  • Answer

    After the calculation is aborted due to the instability, there will be shown a window with "Calculation Errors and Messages". For each displayed message, you can see a yellow arrow on the screen which will guide you to the location of the instability.  
    In most cases, the error message contains also a FE mesh node number. 
    FE mesh nodes can be found also by using the menu "Edit" → "Find via Number". 

  • Answer

    Yes, it is possible to transfer the sections from one model to another model.

    You can select the sections in the original model and then transfer them with [Ctrl+C] and [Ctrl+V].

  • Answer

    Yes, you can define the required glass pane structure in tab 1.2 Layers. To be able to define insulated glass, you have to assign at least one glass layer to the structure. Then, you receive the additional option for the gas layer.
    After defining the gas layer, you receive additional tabs where you can enter more specific data for the design.

  • Answer

    The program RX-TIMBER Brace is usually used for the calculation of the stiffening of double-tapered beams with a variable cross-section height. They can be designed in the program RX-TIMBER Glued-Laminated Beam.

    From the program RX-TIMBER Glued-Laminated Beam, the user receives the equivalent loads per beam classified for each load case. The calculation is performed according to Section 9.2.5.3 of EC5. This equivalent load must be transferred in the program RX-TIMBER Brace for the identical load cases (Figure 1).

    Again, the axial forces calculated by the program RX-TIMBER Brace must be defined as additional forces in the program RX-TIMBER Glued-Laminated Beam. In this case, a distinction must be made between the compression force in the top chord of the brace and the tension force in the bottom chord of the brace. Both axial forces must be applied separately. The tension forces of the bottom flange are used to derive a deflection force in the spatial system, which can be applied as an additional moment (Figure 2).


  • Answer

    You can open your own programs in the menu "Add-on Modules> "Add-on modules".

    To do this, open the file "C: \ Program Files \ Dlubal \ RFEM 5.XX \ RFEM.ini" with a text editor. The text editor must run with administrator rights.

    The following three lines show how the Windows text editor Notepad can be inserted in the menu as an example:

    ModuleName2 = Notepad
    ModuleExeName2 = C: \ WINDOWS \ System32 \ notepad.exe
    ModuleDescription2 = Editor

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