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Frequently Asked Questions (FAQ)
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AnswerThe asynchronous calculation is used if a self-created program should only open or continue RFEM or RSTAB. When the calculation is complete, the event is transferred via a delegate. You can find a C # example in a Visual Studio project in the download area below.
During the calculation, I receive an error message in RFEM with the error number 1639 or in RSTAB with the error number 1640 "Member No. XY | Member Hinges No. YZ are freely rotating about the x-axis. Please check this in Table 1.17 (or 1.7 in RSTAB) or in a related table. " How can I solve this problem?
AnswerIn fact, this error message appears only if a member end release that allows a rotation about the local x-axis has been assigned to a member at both ends. Thus, the member can rotate freely about its own axis and is therefore unstable.Assign a new release to one of the member ends where the degree of freedom φx is not hinged.
AnswerIn Table 1.3 Surfaces, you can specify the parameters in the corresponding tab for the automatic determination of the creep coefficient and shrinkage strain. It is also possible to enter user-defined values there, if necessary.
RSTAB is a FEM program that uses trigonometric trial functions for the members. For this reason, members do not have to be subdivided for sufficiently accurate results and the calculation speed is correspondingly higher.
RSBUCK determines the eigenvalues of the stiffness matrix and can thus linearly calculate the critical load and buckling mode of the structure.
AnswerWith the 'RF-MAT NL' add-on module, it is possible to use the nonlinear material model 'Isotropic Damage 2D/3D' in RFEM to define the stress-strain curve for the steel-fiber concrete. The internal forces and the deformation can be determined in the subsequent nonlinear FE calculation.
A load-deformation diagram for any node of a model (Figure 1) can be defined as a user-defined calculation diagram within the calculation parameters (button or menu 'Calculation' → 'Calculation Parameters') and displayed with the corresponding results:
- To set the desired load increments within the global calculation parameters, see Figure 2
- Definition of a user-defined calculation diagram within the 'Calculation Diagrams' tab: For the selection of the load case, the corresponding node, and the result types of the horizontal and vertical axis see Figure 3
It is possible to switch off displaying of the warning messages before the calculation by using the "Display Warning Messages before Calculation" check box in the program options (Figure 1).
AnswerIn RF-CONCRETE Members, you can design result beams. If the result beams to be designed are defined incorrectly so that no internal forces can be determined for them, a warning message appears when designing in RF-CONCRETE Members. The result beams that have been defined incorrectly can be found by displaying the output of member internal forces. These result beams must be modified accordingly.In this example, there is no output for internal forces related to the result beam 2. Instead of surface 2, surface 1 was mistakenly specified as the included object for this result beam (Figure 2).
Exporting nonlinear stiffness to cracked structures can be enabled in Settings for non-linear calculation of RF-CONCRETE Members or RF-CONCRETE Surfaces. In the Edit Load Cases and Combinations dialog box, check the additional options for the selected combinations. A new tab appears where the stiffness transfer from the additional modules can be switched on.
AnswerWith the RFEM program, you can determine the center point of a system. This is explained in this FAQ .However, the center point does not have to be necessarily confused with the stiffness center. It can be determined with the program SHAPE-THIN according to the theory of stiffening systems. The following webinar will also explain the practical application of the stiffness center in the seismic design.To determine the center, it is also possible as a third and final option to consider the stiffness with a stiffness model in RFEM. In this series of technical articles, this will be explained in the following articles.
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