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Frequently Asked Questions (FAQ)
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AnswerIn the "Edit Load Cases and Combinations" dialog box, you can specify in the bottom right of the "Combination Expressions" tab which method of analysis should be used as the basis for the generated load combinations. By default, the linear calculation according to the geometrically linear analysis is preset for load cases and the nonlinear calculation according to the second-order analysis for load combinations.Thus, you can quickly determine whether the load case or the load combination is calculated according to the geometrically linear, second-order, or large deformation analysis. The postcritical analysis option allows you to carry out the stability analysis according to the large deformation analysis with regard to the post-critical failure of the entire structure.In case the model includes cable members, the calculation according to the large deformation analysis is preset in all cases.
Only the default setting of 1 load increment can be set when a complex nonlinear material model is defined. The reason for this is because the program cannot determine the correct material stiffness for each incremental loading amount. The exact maximum load needs to be applied to the structure in order to determine the state of the material's stress/strain diagram.Figure 01 - Material Model - Nonlinear material definedThis setting can be found and changed under "Calculation Parameters" as well as under the "Calculation Parameters" in the load cases and combinations dialog box.
AnswerThe following code shows how to get different calculation parameters via the COM interface. It also shows how to specify the setting for deactivating shear stiffness:' get model interfaceSet iApp = iModel.GetApplication()iApp.LockLicense' get calculation interfaceDim iCalc As RFEM5.ICalculation2Set iCalc = iModel.GetCalculation' get surface bending theoryDim calc_bend As RFEM5.BendingTheoryTypecalc_bend = iCalc.GetBendingTheory' get settings for nonlinearitiesDim calc_nl As RFEM5.CalculationNonlinearitiescalc_nl = iCalc.GetNonlinearities' get precision and tolerance settingsDim calc_prec As RFEM5.PrecisionAndTolerancecalc_prec = iCalc.GetPrecisionAndTolerance' get calculation settingsDim calc_sets As RFEM5.CalculationSettingscalc_sets = iCalc.GetSettings'get calculate optionsDim calc_opts As RFEM5.CalculationOptionscalc_opts = iCalc.GetOptions' set ShearStiffness to falsecalc_opts.ShearStiffness = FalseiCalc.SetOptions calc_optsUnder Downloads, you can find the EXCEL macro.
AnswerYou can access the results of the individual load increments by activating the "Save the results of all load increments" option in the calculation parameters of the load case or load combination (see Figure 01).
By using the "Calculation Diagrams" window in the calculation parameters, it is possible to additionally evaluate the individual results for the selected elements (see Figure 02). It is also possible to easily create several calculation diagrams.
AnswerA pre-deformed equivalent model is not automatically activated for load combinations. You have to set this manually in the calculation parameters of the load combination. There, select the "Extra options" check box and activate the "Initial Deformation from Module RF-IMP" option.To activate the option in several load combinations at the same time, use the option to select several load combinations.The calculation with the pre-deformed FE mesh is performed if the corresponding load combinations will be calculated according to the second-order or the large deformation analysis.
AnswerIn the Edit dialog box of the respective surface, in the "Modify Stiffness" tab, you can select which type of stiffness modification is to be performed. For example, you can use "Multiplier Factors" as shown in Figure 01.Multiplier factors can be specified for various stiffness components (for example, membrane stiffness).Whether these factors or the defined stiffness modification will be applied in the individual load cases or load combinations is controlled via the calculation parameters. Now, this means that the modification is taken into account as soon as the check box shown in Figure 02 has been selected. When unselecting the check box, the modification will not be considered for the surfaces.Thus, it is possible to control the stiffness modification by load case or by load combination.
The nonsymmetric solver is able to improve the convergence. However, it should only be activated if there are really convergence problems.
For certain material models, you can also be requested to activate the nonsymmetric solver.
In the case of the "normal" equation solver, it is necessary to only save one side of the matrix as it is symmetric to the main diagonal. In the case of the nonsymmetric solver, it is necessary to save both sides and also create them previously, of course. This requires more memory and longer processing time.
For a model that converges well anyway, the nonsymmetric solver only leads to a longer computing time and is of no use.
AnswerThis option is also available in RSTAB for members. This option can be activated in the "Calculation Parameters" of a load case under "Modify Stiffnesses".
AnswerWhen creating a load combination, the calculation type "II. Order "default. For linear systems, however, which are statically indeterminate, the results for load cases, which are calculated by theory according to the first order, can therefore differ.
Please check if the iterative solver is set. If that is the case, then set the direct solver.
Open the calculation parameters (menu Calculation> Calculation Parameters) and check if the direct solver is set (see Figure 1).
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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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