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• ### For a tapered member, I get the error message "Invalid (incompatible) arrangement ...". What can I do?

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A taper describes a member or a surface with a variable cross-section. The cross-section type must be consistent, for example, I-shaped cross-sections at both member ends.

In our example, we have a member with a PRO cross-section and a QRO cross-section.

To create a tapered member here, you should use a parametric cross-section for the member start and end:

This allows you to calculate the tapered member.

• ### How can I teach the program that it automatically increases the longitudinal reinforcement when calculating the deflection of the slabs so that the specified deflection is met?

An automatic increase of the reinforcement for the deformation analysis is not possible. As soon as the deformation calculation is based on the determination of the stiffness, it is not expedient to develop an algorithm that B. increases the reinforcement at the point of maximum deformation. Such a procedure would not result in the deformation being reduced.

Therefore, the reinforcement must be increased manually.

• ### I calculate the deformations at time 0 and at time infinite. The deformations at the time infinite seem plausible to me. The deformations at time 0 seem significantly smaller and therefore implausible. What is the reason?

Please check if the structure tears due to pure load. It is possible that the increase in deformations is mainly caused by creep and shrinkage, which are not active at time 0. In the nonlinear calculation, shrinkage is considered as a strain load, which can cause additional stresses.
• ### I have defined a wind profile for RWIND Simulation up to a height of 100 m. Is the wind profile dependent on the size of the wind tunnel?

In the wind profile, you always define the height ranges from z. B. 0 - 5 m, then 5 m - 10 m, etc. If your wind profile ends at 100 m, it is not cut off, but the value for 100 m is also applied for greater heights. If your wind tunnel is smaller than the stored profile, only the wind speeds up to this height are considered.

You can check this visually by displaying the velocity vectors and deactivating the display on a reduced area.

For a wind tunnel with a height of 50 m, you get the following result:

For a wind tunnel with a height of 150 m, you get the following result:

• ### As part of my bachelor thesis, I would like to integrate the RSTAB printout report into LaTeX. There, you can completely integrate a PDF document as shown in the viewer. This also works with any PDF document, but not with the printout report created by RSTAB. What could be the reason?

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You can include the RSTAB printout report if you print it with a virtual PDF printer, for example PDF24.

It is necessary to pay attention to the PDF created by RSTAB or RFEM for "optimizing the web". Then it can be easily inserted into scientific programs.

• ### I would like to design an aluminum or lightweight structure. Is it possible to use RFEM or RSTAB for this?

Both RFEM and RSTAB can be the solution . For both programs, there are standards available with which the aluminium and light-weight structures can be calculated and designed.
In addition to Eurocode 9 with numerous National Annexes, the American standard ADM 2020 is also available.

Further add-on modules for membrane and cable constructions complete the options.

###### Main Programs RFEM or RSTAB
The main programs RFEM or RSTAB are used to define structures, materials, and actions.

If you also want to analyze membrane and cable structures, you need RFEM . When it comes to pure beam structures, the purchase of RSTAB is sufficient. In any case, RFEM is the more diverse option because it can be equipped and extended with the corresponding add-on modules for all materials and designs.

###### Available standards
• RF-FORM-FINGING/RF-CUTTING-PATTERN (only for RFEM)
Determines the shape and cutting pattern for cutting membranes
• RWIND Simulation
Complex analysis of any structures in the digital wind tunnel with transfer of load cases to RFEM or RSTAB for further processing.
###### Dynamic analysis
If it is necessary to perform seismic analysis or vibration designs of a building, the RF‑/DYNAM Pro add-on modules provide special tools for determining natural frequencies and mode shapes, for an analysis of forced vibrations, a generation of equivalent loads, or for a nonlinear time history analysis.

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If you have any question about the Dlubal Software programs, please do not hesitate to contact our sales department.
• ### Does the program use different values of modulus of elasticity for different temperatures? How to activate it?

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Temperature-dependent stress-strain properties of an elastic isotropic material can be defined in a diagram or imported from [Excel]. These properties are considered for member and surface elements subjected to thermal load (changes or differences in temperature).

The Reference temperature defines stiffnesses for the members or surfaces that have no temperature loads. For example, if a reference temperature of 300 °C is set, the reduced elastic modulus of this point of the temperature curve is applied to all members and surfaces.

The Options dialog section allows you to control if the Poisson's ratios that are applied to the complete temperature diagram are identical. Clear the check box to access the Poisson's Ratio table column for individual entries.

You have to select and define the Temperature/Modulus diagram by your own.

• ### How can I set the deformation coefficient kdef in the program?

The setting for the deformation coefficient kdef can already be made in the model data. There, you can specify the deformation coefficient manually or select it based on the service class.

The deformationfactor k def is considered in the load combinations for serviceability in the program (similar to DIN EN 1995-1-1, 2.2.3).

For the design of mixed structures made of timber materials, see FAQ 4325 .

• ### I would like to move some elements. When moving, my members are deleted, what is the reason?

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You have probably created nodes that were automatically generated by the program and thus locked.

You can unlock these nodes by selecting the nodes and then editing them. There you will find the option to unlock the nodes.

• ### I am using COM interface and Grasshopper for the calculation of complicated structures. For this task I need to create NURBS lines. Could you explain how NURBS should be set? For example what kind of data should be provided for Knots?

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In the FAQ downloads you'll find a sample code how to set NURBS surfaces. The knot vector KnotsX, KnotsY determines how the control points affect the NURBS curve. The number of knots is equal to the number of nodes plus order.

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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.

#### Your support is by far the best

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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. ”