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Frequently Asked Questions (FAQ)
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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: Select the load case, the corresponding node, and the result types of the horizontal and vertical axis, see Figure 3
AnswerIn the case of long crane runways and many cranes, the large number of load combinations can lead to a long calculation time. The following settings affect the calculation time significantly:
Method of calculation for determining internal forces
The fast calculation type may therefore be useful for the preliminary design.
- Fast calculation (calculation of all load combinations according to the 1st-order analysis, then calculation of the governing load combinations according to the second-order bending-torsion analysis)
- Detailed calculation (calculation of all load combinations according to second-order bending torsion analysis)
Desired maximum length of the finite elementsThe maximum length of the finite elements generated for the calculation according to the second-order analysis for flexural-torsional buckling analysis can be entered within a range of 100mm to 2500mm. A finer division of finite elements significantly increases the calculation time.Thus, you should select a reasonable length of the finite elements for an optimized calculation time depending on the structural system. In general, eight elements per beam surface are sufficient to calculate the deformations with a deviation of less than 5% relative to the exact solution.
Number of load combinationsYou can use a reasonable setting of the moving step to control the number of generated load combinations. When entering the moving step, the generated number of crane load positions and load combinations is already displayed in a preview. A small increment results in many load combinations that take more time in the calculation.
AnswerThe operation of the software makes it possible to consider for the descent of loads in RSTAB / RFEM and the checks in the additional modules the following types of bar:
To prevent the automatic division of the existing bar, it is necessary to disable the option "Automatically connect the lines / bars" in the context menu accessible by a right click in the modeling window.
- simple bar : the bar has two knots, one at the beginning and one at the end of the bar Multiple simple bars can be grouped together to form a continuous bar or set of bars
- continuous bar without intermediate cutting at nodes
AnswerEach module has its own method for calculating a case in a module. Here are the methods of the individual modules for the case calculation:RF-/Timber - IModuleCase -> Calculate()RF-/STEEL EC3 - ICase -> moCalculate()RF-/ALUMINUM - ICase -> moCalculate()RF-/STEEL - IstCase -> stResultsCalculate()RF STABILITY - IsbCase -> sbResultsCalculate()RF-/DYNAM Pro - IDynamModule -> Calculate()RF-/CONCRETE Members - IcoCase -> coResultsCalculate()RF-/CONCRETE Surfaces - IcoCase -> coResultsCalculate()
In 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).
There is no general answer to this problem. In the RF-/STAGES add-on module, however, there is a particularity regarding the structural system. Similar to some other add-on modules such as RF-/STEEL Warping Torsion, it is possible to consider the structural system detached from the main program. Thus, there are some advantages regarding the definition of structural states, etc. However, this possibility means that modifications in the main program RFEM or RSTAB are not updated automatically with these add-on modules. Such an update would inevitably lead to incorrect calculations and is therefore blocked.
You can access the results of the individual load increments by activating the "Save the Results of Load Increments" option in the calculation parameters of the load case or load combination (see Figure 1).
By using the "Calculation diagrams" window in the calculation parameters, it is possible to additionally evaluate individual results for selected elements (see Figure 2). It is also possible to easily create several calculation diagrams.
AnswerIt is often the case that the member dimensions do not match.In the example model, the beam has a flange width of 200 mm and the column support of 160 mm.This joint is not allowed in the add-on module because the flange width of the column should be at least as large as the flange width of the structural element to be connected. As soon as the cross-sections are defined according to this rule, the connection design is also satisfactory.
It is not possible to outsource the calculation to a cluster for RFEM.
One way to relieve the workstation computer of complex calculations is as follows: Installation of RFEM on a well-equipped terminal server .
Each employee who has to carry out complex calculations will be provided with access to the server via remote desktop.
Network licenses are required for this option.
AnswerBy default, the compute core of the cross-section program SHAPE-THIN is used in the RF-/ALUMINUM add-on module to determine the stresses of the effective cross-section in an iterative procedure. This method is precise because all vertices and edges of the cross-section are considered, but can be very time-consuming for complex sections.Alternatively, it is possible to determine the effective cross-section by means of a simplified analytical method (see Figure 01) that runs much faster. Using that approach, corners, roundings, etc. are neglected and subsequently compensated by a factor. No iterative calculation is performed. Therefore, the effective cross-section values may be higher than with the SHAPE-THIN calculation.In such a case, it is recommended to carry out the calculation with the analytical method and then to design only the governing structural component with the governing load combination by means of the SHAPE-THIN solution.
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