# Frequently Asked Questions (FAQ)

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• ### How would you best model hold down elements within panels?

New FAQ 004201 EN

#### Answer

In a short overview, creating hold down elements involves modeling rigid links and adding in nodal supports with non-linearity settings that allows the supports to take only tension forces. A line support is added at the bottom of the wall that only takes compression forces. The individual nodal supports connected with rigid members only take tension forces.

A more detailed look on how these elements can be model can be seen in the video below.
• ### Why are there no resultant support forces for result combinations?

New FAQ 004200 EN

#### Answer

For a resultant, a concrete combination of loads is required, which result combinations can not provide.

The following example shows the problem quickly. A single-span beam is loaded with three different load cases. For the support at node 1, the result envelope of the 6 possible load combinations results in a maximum PZ of 11.25 kN from the result of CO 2 (see Figure 01). The support at node 2 has a maximum PZ of 12 kN from the result of CO1. However, the resultant of 23.25 kN does not occur in any of the involved load combinations and is therefore too large (maximum CO 1 and CO 2 with 22.5 kN).

The situation is similar with the pure result combination from the load cases, which have the same maximum values PZ of the nodal supports 1 and 2. However, it is not apparent here that a resultant would give incorrect results.

For result combinations, resultants are not used for result combinations because the results may be incorrect.

• ### How can I create an imperfection via the COM interface?

New FAQ 004199 EN

#### Answer

An imperfection is considered load and is transferred via the interface of the load case. Provided that the interface to the model has already been fetched, the interface to the loads (ILoads) is retrieved, followed by the interface to load case 1 (ILoadCase), if it has already been created:

'set loadcasesDim iLoads As iLoadsSet iLoads = model.GetLoads        'get load case.'Dim iLc1 As ILoadCaseSet iLc1 = iLoads.GetLoadCase (1, AtNo)        'define imperfectionDim imperf As Imperfectionimperf.Comment = "test"imperf.Direction = LocalZTypeimperf.Inclination = 200imperf.no = 1imperf.ObjectList = 1imperf.Precamber = 300imperf.PrecamberActivity = ActivityAccording_EN_1993_1_1        'set imperfection'iLc1.PrepareModificationiLc1.SetImperfection imperfiLc1.FinishModification

The data of the imperfection is then filled out first, here for member 1, and then transferred within a Prepare-/FinishModification block of the load case Interfaces.

• ### How can I retroactively change a member via the COM interface?

New FAQ 004195 EN

#### Answer

To modify an existing element, you have to get the interface to the corresponding element, here an example of a member:

Dim iModel As RSTAB8.modelSet iModel = GetObject (, "RSTAB8.Model")iModel.GetApplication.LockLicense    Dim iModData As IModelDataSet iModData = iModel.GetModelData    Dim iMem As RSTAB8.IMemberSet iMem = iModData.GetMember (1, AtNo)

Use this code to get the interface to member 1, which must already be created. Then, you can use the .GetData () method of the interface to get the member data.

If you want to modify data (such as the member rotation here), you can subsequently transfer it to the program within a Prepare-/FinishModification block with the method .SetData ().

Dim mem As RSTAB8.Membermem = iMem.GetData    mem.Rotation.Angle = 0.5mem.Rotation.Type = RSTAB8.Angle   iModData.PrepareModificationiMem.SetData memiModData.FinishModification
• ### Why are imperfections taken into account in RFEM and RSTAB when calculating according to the linear static analysis, even though no component deformations are considered according to the linear static analysis?

New FAQ 004193 EN

#### Answer

In general, an imperfection describes the imperfection of a structure or the deviation due to its production from the ideal shape. There are different ways to simulate the imperfection. In RSTAB and RFEM, imperfections are represented as equivalent loads. The definition of equivalent loads is shown in Figure 01 and is taken from [1] . The same is described in EC3 [2] . Since these are equivalent loads that are dependent on the axial force, they are also taken into account for a calculation according to the linear static analysis. It is recommended to manage loads and imperfections in separate load cases. They can be suitably combined with each other in load combinations. For the load case general data (see Figure 02), load cases with pure imperfection loads have to be classified as the action type "Imperfection".
• ### How is it possible to change the steel rebars sizes from the American Standard (#3,#4..etc) to millimetres in RF-CONCRETE Members while using ACI?

New FAQ 004192 EN

#### Answer

You will find an option in the "Settings" of the add-on module (see picture 01).
• ### "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?

New FAQ 004188 EN

#### Answer

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.

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.

• ### For reinforced concrete design, I have purchased the "EC2 for RFEM" add-on module. Where can I start this module?

New FAQ 004187 EN

#### Answer

In this sense, "EC2 for RFEM" is not an add-on module that you can start separately, but a standard according to which you can design reinforced concrete components, for example in RF-CONCRETE Surfaces or RF-CONCRETE Members.

You can find the selection of the design standard in the respective module in the "General Data" dialog box.

The same applies to "EC2 for RSTAB".

A design standard, here the "EC2", is required in the following add-on modules:

- RF-CONCRETE in RFEM 5
CONCRETE in RSTAB 8
- RF-/CONCRETE Columns in RFEM 5 and RSTAB 8
- RF-PUNCH Pro (only available for RFEM 5)

• ### Which programs and modules does Dlubal Software have for solid construction?

New FAQ 004186 EN

#### Answer

As a general solution, RFEM and RSTAB are the ideal solution . In addition to the Eurocode 2 , international standards such as ACI 318 , CSA A23.3, SIA 262 or GB 50010 are available for the design for both programs.

With add-on modules for columns, foundations, or punching designs, you can design structural components quickly and safely.

###### Basic programs RFEM or RSTAB
With the basic programs RFEM or RSTAB structures, materials, and which are impact defined.

For solid construction, RFEM is clearly the first choice , because in addition to the possibility to create spatial frameworks, plates, disk and shell structures can be additionally processed. RFEM is the more versatile option because it can be equipped and extended with the corresponding add-on modules for all materials and designs.

###### Available standards
• Eurocode 2 (EN 1992-1-1)
• SIA 262
• ACI 318
• CSA A23.3
• GB 50010
###### Dynamic Analysis
If earthquake calculations or vibration analyzes are necessary for the building, the RF-/DYNAM Pro add-on modules provide suitable tools for determining natural frequencies and shapes, analysis of forced vibrations, generation of equivalent loads, or for the nonlinear time history analysis.

If you have any questions about the Dlubal software, contact the sales department
• ### How can I set the calculation parameters with the help of the COM interface?

New FAQ 004184 EN

#### Answer

The following code shows how to get different calculation parameters via the COM interface. It also shows how to specify a setting for deactivating shear stiffness:

'get model interface'Set iApp = iModel.GetApplication ()iApp.LockLicense    'get calculation interfaceDim iCalc As RFEM5.ICalculation2Set iCalc = iModel.GetCalculation    'get surface bending theory'Dim calc_bend As RFEM5.BendingTheoryTypecalc_bend = iCalc.GetBendingTheory    'get settings for nonlinearities'Dim calc_nl As RFEM5.CalculationNonlinearitiescalc_nl = iCalc.GetNonlinearities    'get precision and tolerance settings'Dim calc_prec As RFEM5.PrecisionAndTolerancecalc_prec = iCalc.GetPrecisionAndTolerance    'get invoice 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_opts
In the appendix, there is an EXCEL macro to download.

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#### 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.

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