#### Further Information

In addition to our technical support (e.g. via chat), you’ll find resources on our website that may help you with your design using Dlubal Software.

Receive information including news, useful tips, scheduled events, special offers, and vouchers on a regular basis.

• ### How can I set as quickly as possible that the load combinations generated by the program will be calculated according to the geometrically linear analysis, for example?

004331

In 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.
• ### "During the calculation of material non-linearity, the material with a decreasing branch of the diagram can be calculated with one load increment only." Why do I get this error?

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 defined

This setting can be found and changed under "Calculation Parameters" as well as under the "Calculation Parameters" in the load cases and combinations dialog box.

• ### How can I set the calculation parameters by using the COM interface?

The 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 interface    Set iApp = iModel.GetApplication()    iApp.LockLicense        '   get calculation interface    Dim iCalc As RFEM5.ICalculation2    Set iCalc = iModel.GetCalculation        '   get surface bending theory    Dim calc_bend As RFEM5.BendingTheoryType    calc_bend = iCalc.GetBendingTheory        '   get settings for nonlinearities    Dim calc_nl As RFEM5.CalculationNonlinearities    calc_nl = iCalc.GetNonlinearities        '   get precision and tolerance settings    Dim calc_prec As RFEM5.PrecisionAndTolerance    calc_prec = iCalc.GetPrecisionAndTolerance        '   get calculation settings    Dim calc_sets As RFEM5.CalculationSettings    calc_sets = iCalc.GetSettings    'get calculate options    Dim calc_opts As RFEM5.CalculationOptions    calc_opts = iCalc.GetOptions        '   set ShearStiffness to false    calc_opts.ShearStiffness = False    iCalc.SetOptions calc_opts
• ### Can I display the results of the individual load increments after the calculation?

You 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.
• ### I have generated a pre-deformed equivalent model using RF‑IMP by means of a pre-deformed FE mesh. Is the equivalent model considered for all load combinations nov, or do I have to make further settings?

A 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.
• ### How can I control the stiffness reduction by load cases for surfaces?

In 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.
• ### What is the use of the nonsymmetric solver?

003008

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.

• ### In RFEM, I have the option to deactivate objects of the structure. Is this also possible in RSTAB?

This option is also available in RSTAB for members. This option can be activated in the "Calculation Parameters" of a load case under "Modify Stiffnesses".
• ### Why do the results of a combination of load cases differ from the EK formed from load combinations?

002888

When 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.
• ### The calculation in RFEM takes a very long time. However, the processor load is low. How can it be accelerated?

002864

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).

1 - 10 of 14

If not, contact us via our free e-mail, chat, or forum support, or send us your question via the online form.

#### First Steps

We provide hints and tips to help you get started with the main programs RFEM and RSTAB.

#### 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.

#### Your support is by far the best

“Thank you for the valuable information.

I would like to pay a compliment to your support team. I am always impressed how quickly and professionally the questions are answered. I have used a lot of software with a support contract in the field of structural analysis, but your support is by far the best. ”