The RF-STABILITY and RSBUCK add-on modules for RFEM and RSTAB allows you to perform eigenvalue analysis for frame structures in order to determine critical load factors including the buckling modes. It is possible to determine several buckling modes. They provide information about the model areas bearing stability risks.
The critical load factor is always determined for the entire structure. Based on this, the corresponding critical loads of the individual members, effective lengths, and effective length factors are calculated.
A simple example of a rigid column with load introduction on the head (for example roof loads) and on the top third (for example crane loads) exemplifies the procedure in detail.
For the structural system, the critical load factor of 8.591 has been determined. This is to be multiplied by the normal forces of members to obtain the critical loads.
Member 1: Ncr,1 = 8.591 * 550 kN = 4725 kN
Member 2: Ncr,2 = 8.591 * 200 kN = 1718 kN
The corresponding effective lengths for buckling about both axes are calculated by using the adjusted formula Ncr = E x I x pi² / Lcr. Finally, the effective load factors are determined from the relation kcr = Lcr / L.
Now, it is possible to perform equivalent member design according to EN 1993-1-1. The critical load factors calculated in RF-STABILITY or RSBUCK can be transferred directly into the RF-/STEEL EC3 add-on module. Depending on the model complexity and loading, you should always check whether the stability design using imperfections and internal forces according to the second-order analysis would be a better alternative.
In order to use the working window area for graphical input of model data or for result evaluation in an optimum way, there are various options for arranging the Project Navigator, the table and the result panel.
1. You can hide them completely by clicking the corresponding button in the toolbar or by [X] in the title bar of the dialog box.
2. You can dock them onto any screen edge by dragging and dropping the title bar of the dialog box. For this, there are the icons for docking in the middle of the screen. If you drag the dialog box to one of these docking points, it is adapted automatically between the existing dialog boxes. If you drag the dialog box to the docking icon on the screen edge, it is placed over the entire width of the screen.
3. If there are two screens available, it is possible to undock the elements from the program interface and place them on the second screen by using drag & drop.
4. Furthermore, you can combine the Project Navigator, the table and the result panel in a single dialog box where a dialog box is dragged on the title bar of another one.
The network licenses of Dlubal Software provide a very convenient solution for an engineering office as well as for a user who is often on the move. It can be helpful if you are on a consulting meeting with the building owner and want to directly apply the current changes and show the solution immediately. You only need the Internet and VPN connection in your office and you can access all your purchased licenses.
In order to quickly find the license server, you can save the IP address of the network dongle computer in Admin Control Center (available on http://localhost:1947) under “Remote License Search Parameters” that can be found under “Configuration” in the “Access to Remote License Managers” tab.
As of the program version RFEM 5.06, it is possible to edit several tendons in the RF-TENDON add-on module at the same time. For this, it is necessary to select the corresponding tendons in the table of tendon arrangement.
This can be done by
~ constantly pressing the left mouse button and marking the tendon numbers,
~ pressing the Shift key and selecting the first and the last tendon number,
~ pressing the Ctrl key and selecting the desired tendon numbers by clicking the left mouse button.
RFEM and RSTAB provide the option to create national annexes with user-defined partial safety factors and combination coefficients. It is also possible to transfer them to other computers.
The user-defined national annexes are stored in the “KombiNorm.dat” file. In the case of the default installation of RFEM or RSTAB, you can find the file in the following directory:
C:\ProgramData\Dlubal\RFEM 5.xx\General Data
C:\ProgramData\Dlubal\RSTAB 8.xx\General Data
If you copy this file into the relevant directory on the target computer, it will be possible to use the user-defined national annexes there, too.
The cross-section properties software SHAPE-THIN allows you to model corners of cross-sections in full detail.
~ The “Smooth Corner” function fills the area with an element and connects it by a null element automatically. For this, simply click the corner.
~ The “Create Round or Angled Corner” function provides the option to round or angle the corner. For this, define the rounding radius and click both elements.
If nodal supports should have an effect in certain directions only, you can define failure. Here is an example of a single-span beam, whose right support can only absorb positive vertical loads. The load comprises vertical suction load and horizontal load. However, there are two options for the failure:
1) Failure if negative PZ’
2) Failure all if negative PZ’
The difference is illustrated in the graphic.
If there are additional horizontal forces after the vertical failure of the support with Option 1, the support with Option 2 fails completely. Therefore, it is necessary to select the proper nonlinearity according to the circumstances.