Frequently Asked Questions (FAQ)

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Yes, you can optimize cross-sections in the design add-ons (for example, steel design, timber design, and so on).

Optimization can be carried out, for example, for standardized cross-sections of a series or, for parametric cross-sections, for the width, height, and so on.

Select “Steel Design” and “Input Data” in the RFEM table window. Then, in the “Sections” tab, in the “Use Other Section for Design” column, select the “Optimize | Current Series...” option and define the parameters to be optimized:

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RSECTION cross-sections can be defined in Grasshopper using a model template.

Creating Template with RSECTION Cross-Section

Import your RSECTION cross-section to RFEM 6:

• Import RSECTION Cross-Section

Then, save the RFEM file as a template (*.ft6 file):

• FAQ | How can I create a model template in RFEM 6?

Reference to Template in Grasshopper

In Grasshopper, you can access this template file by entering the path of the saved RFEM template file in the export component (Use Template).

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You can view the design check details for both the design checks and for determining the reinforcement as part of the concrete design.

1 – Details for Design Checks

To do this, select the resulting design ratio for members, surfaces, and so on, in the table window for the concrete design.
For each design result, double-click the respective design ratio result in the table to open the window with the corresponding design check details.

2 – Details for Reinforcement Determination

To do this, select the resulting Reinforcement on members, surfaces and so on, in the table window for the concrete design.
For each reinforcement result, double-click the respective value in the table to open the window with the corresponding details for determining the reinforcement.

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In the case of models with membranes / cable members, an initial prestress allows for the convergence of the calculation. In RFEM 6, there are two options for considering the initial prestress: an initial state or a minimum change in length. In addition to numerical convergence, it is even more important to consider that the natural frequencies of a cable depend on the initial tension: it is necessary to have a tensile load, and its magnitude influences the results.

For a simply supported cable with only self-weight, a modal analysis without an initial state is defined:

The result is the error message “10060 - The stiffness matrix is singular | The structure is unstable”:

The first solution is to select a load case with tensile force as an initial state. In this case, considering the nonlinearities (third-order analysis) of a cable element, a horizontal reaction results from a pure vertical load. The horizontal reaction corresponds to a tensile force. It's important to emphasize that the load cases or load combinations of the "Mass Source" option have no influence on the stiffness matrix. Therefore, two selections are necessary.

The second option is to define an initial deformation in the modal case setting.

It is recommended to evaluate the influence of the initial values (initial state or minimum change in length) on the vibration modes. Relatively small variations of these values may lead to significant changes in the natural frequencies.

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The need to account for tension member nonlinearities depends on the analysis objective. If the primary aim is to determine base shear forces for comparison with other horizontal actions, neglecting the nonlinearities of tension members is typically acceptable and can be considered a conservative approach. However, for precise design of the tension members themselves, it is essential to consider their nonlinear behavior. Methods such as deactivation should be employed to accurately capture these effects and ensure the integrity and safety of the design.

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If you want to combine several members of a member set into one member again, proceed as follows:

Step 1

Select the relevant members and thus the corresponding lines. Open “Join Members”.

The previously selected members and lines are now merged in a single line and a member.

Step 2

Select the line that has just been merged and edit it. It is necessary to delete all nodes on the line. The first and last nodes listed always correspond to the start and end nodes. Thus, the nodes 59, 95, 131, and 167 would have to be deleted here.

Click “OK” to close the dialog box.
Important: No nodes on member will be deleted, this only concerns nodes on line.

Step 3

Next, it is necessary to select all intermediate nodes on the member so that you can edit them. To do this, open the editing dialog box for the nodes. In the “Main” tab of the node editing dialog box, you need to change the node type to “On Member.” If you have done everything correctly, the corresponding member is automatically displayed in the “On Member” tab under “Parameters | Member No.”

Close the editing dialog box by clicking “OK.”

Step 4

To check your entries, you can open the member's editing dialog box. The “Nodes on Member” option is now activated there. Click the “Nodes on Member” tab to open the dialog box where you can find a list of the nodes that you have edited.

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Yes, to do this, simply use the “Cancel Generated State” option for a base object that has been generated. The following image shows this button for a beam member that was automatically generated from a beam panel:

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Treating a connection as fully rigid assumes that the joint can transfer large bending moments without any relative rotation between connected members. While this approach reduces the bending stress in the beam itself, it can lead to an uneconomical design. The joint must be oversized to accommodate the high moment, leading to increased material costs and potentially more complex fabrication. Moreover, this rigid connection may not reflect the actual behavior of the structure under real loading conditions, which could result in overdesigning the joint and thus failing to achieve cost-efficient material use. Instead, considering more realistic connection stiffness could optimize both the joint and overall structure design.

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Modeling a cantilever using surface elements provides a more accurate representation of local buckling behavior. Modeling it as a member may give a reasonable displacement result, but the critical load factor and buckling modes might not be realistic, especially when considering local buckling.

For more information, see our KB article on this topic:

• KB 1931 | Structure Stability: Buckling Shape of Cantilever

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RFEM 6 offers several methods for modifying surface stiffness, each suited for different applications. Here's a breakdown of the best use cases for each method:

• Total Stiffness Modification

This method is best for global adjustments to simulate surfaces with increased or reduced stiffness or for simplified modeling of surfaces with consistent material properties. It involves uniformly scaling all elements of the stiffness matrix by a single factor.

• Partial Stiffness, Weight, and Mass Modifications

Use this method for targeted modifications where you need to adjust specific components of the stiffness matrix while keeping others unchanged. It's useful for simulating complex multi-layered or composite materials and addressing creep and shrinkage effects in composite steel-concrete decks. An example is to address creep and shrinkage effects on a composite steel-concrete deck, where the bending and torsional terms in the surface stiffness matrix can be uniformly scaled down by a factor representing the time-dependent reduction in stiffness.

• Element-Specific Stiffness Modification

This method is particularly useful for simulating complex material behaviors and addressing localized effects within the structure. For example, it can be used for a composite plate with fibers predominantly oriented along the x-axis, resulting in significantly higher stiffness in that direction. To account for this anisotropic behavior, the bending stiffness term k, which corresponds to D11 in the surface stiffness matrix, can be increased while keeping other terms unchanged.

• Standard-Specific Stiffness Modification (ACI 318-19 & CSA A23.3-19)

This method is used to incorporate stiffness reductions for concrete members and surfaces across various element types according to Section 6.6.3.1.1 of ACI 318-19 and Clause 10.14.1.2 of CSA A23.3-19. Options available include cracked and uncracked walls, flat plates, slabs, beams, and columns. The program uses multiplier factors directly sourced from tables in the standards.

Keep in mind that implementing these modifications demands careful evaluation of the structural context and desired objectives, as alterations to the stiffness matrix directly affect the distribution of stresses and deformations within the structure.

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A key advantage of the Building Model add-on is its ability to accurately determine interstory drift, a critical parameter in seismic design. Evaluating story drift is essential for ensuring structural integrity by limiting excessive displacement, which can cause instability or damage to nonstructural components, such as partitions. With this functionality, engineers can also calculate stability factors and interstory drift sensitivity coefficients, helping to assess whether P-delta effects should be included in the seismic analysis. These effects can then be seamlessly integrated into RFEM 6, along with the Response Spectrum Analysis add-on, for a more thorough and comprehensive evaluation of the building's seismic performance.

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The Time History Analysis add-on in RFEM 6 is limited to linear structural systems, meaning nonlinear elements are either ignored or converted to linear equivalents. Therefore, nonlinear time history analysis is not directly supported in RFEM 6 using the Time History Analysis add-on.

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One of the key outputs in RWIND is the wind force coefficient (also known as the aerodynamic force coefficient), which helps engineers understand how wind interacts with a structure. This coefficient is essential for optimizing designs to ensure structural stability and efficiency.

In RWIND, the wind force coefficient is typically obtained by running a wind simulation based on the given geometry, wind speed, and environmental conditions. The software then computes the forces acting on the structure and provides coefficient values that indicate the aerodynamic response. This FAQ will walk you through the process of obtaining the wind force coefficient in RWIND.

To illustrate how RWIND determines the wind force coefficient, we can look at a practical example from RWTH Aachen University about Antenna [1] according to image 1.

In image 2, the value of wind force coefficient (aerodynamic force coefficient) is calculated in info tab of the edit model data. Also the formula of wind force coefficient is show here:

In order to results comparison, image 3 [1] presents an analysis of force coefficients (C_f) in relation to different structural configurations under wind influence. On the left side, a polar plot titled "Kraftbeiwerte C_f" illustrates the variation of the force coefficients at different wind directions according to the reference area A_ref = 0.1127 m². A red dot at 0° indicates the force coefficient in RWIND (C_f = 0.82) as a significant wind-related point for a = 45 mm.

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What is single sign-on (SSO)?

Single sign-on (SSO) is an authentication method that allows you to access multiple independent software systems with a single set of credentials, such as a user name and password. SSO eliminates the need to log in to each system separately, simplifying the log-in process and improving the user experience.

How does single sign-on work in RFEM 6?

RFEM 6 uses single sign-on to simplify the licensing process. Currently, the Microsoft Azure Active Directory account is supported. The implementation of SSO in RFEM 6 is as follows:

1. System account query: RFEM 6 asks Windows for the system account of the currently logged-in user.
2. Silent token acquisition: RFEM 6 tries to obtain an access token for the user in the background and without user interaction.
3. Interactive token acquisition (if necessary): If silent token acquisition fails, for example, because the user is not logged in or no valid session exists, RFEM 6 tries to acquire the access token interactively.
4. Token validation: RFEM 6 validates the obtained access token against the Microsoft Graph API endpoint at https://graph.microsoft.com. This step ensures that the token is issued by Microsoft and is valid.
5. Token submission to Dlubal license server: After successful validation, RFEM 6 sends the access token to the Dlubal license server.
6. User data retrieval and license check: The Dlubal license server also contacts https://graph.microsoft.com to retrieve the email address of the user associated with the access token. Based on this email address, the license server determines the associated company and checks if a valid license for RFEM 6 is available.

What are the benefits of single sign-on in RFEM 6?

• Simplified login process: You do not have to log in every time you start RFEM 6, provided you are already logged in to Windows.
• Increased user-friendliness: Fewer passwords to remember and faster access to the software.

Improved security: SSO can improve security by centralizing password management and reducing the risk of weak or reused passwords.

What are the requirements for using SSO in RFEM 6?

• Corporate account: Your company needs to have an account that is compatible with single sign-on (for example, a Microsoft Azure Active Directory account).
• RFEM 6 license: A valid RFEM 6 license has to be assigned to your company account.
• Internet connection: An active internet connection is required for authentication and license verification.

What can I do if single sign-on does not work in RFEM 6?

• Check your internet connection: Make sure that your computer is connected to the internet.
• Check Windows login: Make sure you are logged in to your Windows system.
• Microsoft account issues: Check if there are any issues with your Microsoft or work account. If necessary, contact your IT administrator.
• RFEM 6 restart: Restart RFEM 6. Sometimes a restart can fix the problem.
• Contact Dlubal Support: If the problem persists, please contact Dlubal Software Support.

Do I need a permanent internet connection to use RFEM 6 with SSO?

No, RFEM 6 does not require a permanent internet connection for continuous use after the license has been successfully activated via SSO. An internet connection is mainly required for the license check when starting RFEM 6. At regular intervals, RFEM 6 can carry out a new license check in the background to ensure the validity of the license.

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Yes, after you have followed the installation instructions at the link below, run the following Python code. Since the model is neither saved nor calculated, no credits will be deducted from your account. However, a subscription is absolutely necessary.

• Documentation API II
• Webshop API (gRPC)
• API (gRPC) Cost

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In the graphic printout dialog box, there is a separate section for controlling the display factors, where you can set the factor for deformations and many other results. The image below shows the corresponding input dialog box.

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Yes, shear panels and rotational restraints can be considered not only in the design add-ons, but also in structural, stability, and modal analyses.

This can be configured within structural modifications. The following manual entry describes the related input:

• RFEM 6 Manual | Structure | Special Objects | Structure Modifications

The image below shows the input for the activation of considering shear panels and rotational restraints:

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Transient wind simulations play a crucial role in analyzing airflow patterns, turbulence, and aerodynamic forces in various engineering applications, such as structural analyses against wind load. Unlike steady-state simulations, transient simulations capture the time-dependent behavior of wind flow, requiring a careful balance between accuracy and computational efficiency.

One of the critical factors in transient wind simulations is determining the sufficient total simulation time to ensure reliable and meaningful results (Image 1). If the simulation time is too short, the flow may not fully develop, leading to inaccurate predictions of key parameters such as velocity, pressure fluctuations, and turbulence characteristics. Conversely, excessively long simulation times can result in unnecessary computational costs without significantly improving accuracy.

The stabilization of both the residuals and the overall drag force (and/or its components) needs to be monitored in transient simulation (Image 2).

By stabilization, obtaining a constant value or a periodic oscillation over time is recommended (Image 3). In case these criteria are not met, it is suggested that the transient calculation be continued, which can be easily done by the users.

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In RFEM 5, the modeling option for couplings in the menu “Insert → Model Data → 1.31 Nodal Constraints” (Image 01) has been implemented to model elements with very high in-plane stiffness. This approach is mainly used in building engineering, where massive horizontal components (for example, floor slabs) justify such an assumption.

Since the “diaphragm” is used almost exclusively in buildings, this function has been transferred to the “Building Model” add-on in RFEM 6. There, you can select from four options to consider the stiffness (Image 02). Thus, the user can choose the model assumptions that best reflect the actual structural system.

A separate result configuration can be defined for each story. With the options “Rigid Diaphragm” or “Semi-Rigid Diaphragm”, slabs (2D analysis) can be modeled together with columns (nodal supports) and walls (linear supports) in a single model. The “Load Transfer Only” option simplifies the calculation by using only slabs for load transfer.

The building model thus represents an alternative to separate modeling of ceilings, in which the tool “Import Support Reactions as Load” was used beforehand. An initial analysis can be carried out using “Load Transfer Only” to determine global parameters, such as support reactions, stability, and the pre-dimensioning of the vertical main supporting elements.

Afterwards, you can activate the other functions of the add-on, for example, story modeling, ceiling sets, wall panels, and wall-like beams, om order to perform a more detailed analysis and design of the materials used (Image 04). However, since this advanced model requires more computing and processing power, a step-by-step approach is recommended. In this way, all components of a project can be integrated into just one model.

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A line hinge/line release is not required for the wall-to-floor connection when using a rigid or semi-rigid diaphragm. This is because rigid and semi-rigid diaphragms have zero flexural out-of-plane stiffness in the global 3D calculation (Image 01).

If no diaphragm or load transfer is selected, a line hinge/line release should be defined.

In the local 2D calculation to consider gravity loads, nodal supports and line supports are defined to represent columns and walls. In most cases, a “Fixed Hinge Support” is adequate, as the joint between a CLT wall and CLT floor can be taken as a hinge connection with free rotation around the global X and Y axes. Alternatively, an elastic column or wall can be assigned (Image 02).

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For RFEM/RSTAB, we recommend the driver from the "Production Branch", as it is more stable and has undergone extensive testing. The "New Feature Branch" may contain experimental features and is less reliable, so we advise against using it.

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Already created multi-prints can be adjusted with just a few clicks. To do this, follow the steps below:

1. Open the relevant printout report (1), for example, by right-clicking the Data navigator.
2. A new dialog appears; click the Edit Multi-Print button in the menu bar (2), and select the multiple print you want to change (3).
3. Check the synchronization of images in the Image Actions tab and adjust it, if necessary (4).

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To generate load combinations that include counteracting dead loads according to Section 4.1.3.2(5), edit the Combination Wizard option (Image 01). In the Standard Options tab, activate the "Combinations from counteracting dead loads" option.

The load combinations including counteracting dead loads are shown in Image 02.

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You can easily adjust the numbering of existing load cases. There are several ways to do this:

Manual (Free) Editing via Program Dialog Box

1. Open the Load Cases and Combinations dialog box.
2. In the Load Cases tab, select the relevant load case in the list (1), enter the desired number (2), and click OK to confirm (3).

Please enter a different number to the relevant load cases first.#/banner#

Automatic Numbering via Table

The procedure is particularly suitable for a continuous numbering of load cases with grouping.

1. In the table, select the Load Cases and Combinations category in the table.
2. In the Load Cases tab, select a) empty rows, and delete them using the shortcut menu, or b) insert new rows.

Fast Numbering via Program Dialog Box

A very simple and fast way to the automatic, consecutive numbering of load cases:

1. Open the Load Cases and Combinations dialog box.
2. In the Load Cases tab, click the button at the bottom of the list for (a) numbering of all existing load cases, or (b) numbering of the marked load cases with a selectable start index.
3. Click OK to confirm.

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The Python console and in-app scripting with Python allow for the integration of external libraries into the code.
There are two simple methods to install external libraries:

1. Installation via console:

The install_packages("packageName") command allows you to install external libraries directly into the Python console of RFEM. Type this command into the console and press Enter to start the installation.

2. Installation via Terminal:

The terminal can be opened by clicking the black button at the top of the console or in the script manager. Enter the command python -m pip install packageName and confirm by pressing the Enter key. The desired library will then be installed in the virtual environment of RFEM.

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Yes, it is currently possible to change the standards indirectly with JavaScript. The following script executes a JavaScript script in RFEM that contains the description of the desired steel structure standard to set the standard in RFEM:

The easiest way to determine the description of the desired standard is to use the JavaScript console in RFEM. To do this, use the command that corresponds to the add-on of interest:

The script adjusts the standard for the Steel Design add-on in RFEM. It can be easily integrated into the existing WebService scripts, thus allowing you to change the standards for all add-ons.

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The file-based data exchange is available for the data exchange between HiCAD and RFEM 6.
The following formats are supported by the programs:

IFC File from HiCAD in RFEM 6

For the export from HiCAD to the IFC format, the model view definitions Design Transfer View and Reference View are available. Both formats can be imported into RFEM 6.

After the import into RFEM 6, the IFC Navigator opens automatically where you can select the imported components. The structure is composed like the group structure created in HiCAD.

You can also control the visibilities using the IFC object types in the navigator.

By right-clicking one or more of the objects, you have the option to convert them into the RFEM objects.

IFC File from RFEM 6 in HiCAD

To exchange an IFC file from RFEM 6, it is important to use the IFC 4 – Reference view file type when saving the data.

You can then import the file into HiCAD using the 3D import.

DSTV Product (.stp) from HiCAD in RFEM 6

To exchange the data in the DSTV .stp format, select the save option More… and DSTV Product in HiCAD.

For the import into RFEM 6, the DSTV option is also available to import this file format.

The Conversion Tables window opens automatically, where you can define the materials and cross-sections.

DSTV Product (.stp) from RFEM 6 in HiCAD

If you export a DSTV file from RFEM 6, you can also import it into HiCAD by opening a DSTV product.

You get there the centroidal lines of the cross-sections in the form of member elements. You can then convert them into cross-sections using the Exchange in Standard Section command.

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When designing a steel joint design, an initial FE model (submodel) of the steel joint is created in the background and calculated by RFEM 6. Therefore, the errors that are not detected during the plausibility check in Steel Joints add-on refer in most cases to this submodel. You can save this and open it as a separate RFEM model in order to analyze it in more detail.
To do this, follow the steps below:

1. Click the "Results in Steel Joint" button.
2. Click the "Save Steel Joint Model As" button.
3. Save the steel joint model.
4. Open it as a separate model in RFEM 6.

Now, you will get all the information about the submodel and can use all the tools of RFEM 6 to find the cause.

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It is also necessary to specify the coefficients for the effective lengths. The top and bottom of the table work together. The upper table shows the segments for the design in each direction. The lower table then defines the effective lengths by means of factors or absolute values.

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