# Frequently Asked Questions (FAQ)

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• ### When trying to calculate the design in RF-STEEL Surfaces, I receive Warning No. 1162 - Surface No. XX is of the type "Orthotropic" and cannot be designed. What does this Warning mean?

New FAQ 004308 EN-US

#### Answer

Orthotropic surfaces are non-linear and cannot be designed within the RF-STEEL Surfaces add-on module. It is still possible to get the full stress analysis in RFEM which can be compared to the limiting stresses manually. Otherwise, the surface will need to be set to "standard" for it to be designable within the add-on module.

• ### In the '1.4 Longitudinal Reinforcement' input dialog box, there is no 'Multiple Selection' of surfaces.I have to edit the concrete cover for many connected surfaces. Is there any help available in this regard?

New FAQ 004288 EN-US

#### Answer

Yes, it is.

It is possible to edit the concrete cover in the first row for the direction d1 and d2 and then switch to the cell in the second line and copy the value from the cell above it with the [F8] key.

This allows you to edit the values relatively quickly for all connected surfaces.

You can also use the button to filter the applied areas to reduce the number of lines displayed. See the link below.
• ### In the '1.4 Longitudinal Reinforcement' input dialog box, I always see all surfaces, although I do not want to check the punching for these surfaces. Can the display of surfaces be limited only to the surfaces to be proved?

New FAQ 004287 EN-US

#### Answer

Yes, it is possible. In the input dialog box '1.4 Longitudinal Reinforcement', there is a filter function.

If you click this button, only the surfaces connected to the punching points are displayed.

• ### Why do the equivalent stresses of RFEM and RF-STEEL differ from each other, although the same CO is considered?

New FAQ 004277 EN-US

#### Answer

It is possible to display or calculate the stresses in RFEM as well as in the add-on module by means of the following smoothing options:

• Constant on elements
• Not continuous
• Continuous within surfaces
• Continuous total
• Continuously by groups or Continuous by groups

To compare the results, the same display type and calculation type must be selected in RFEM and RF-STEEL Surfaces.

In RFEM, it is possible to do this in the Project Navigator Show → Results → Surfaces → Distribution of Internal Forces/Stresses (Figure 02). In RF-STEEL Surfaces, this can be displayed or changed in the Details → 'Options' tab (Figure 03).

• ### Despite having defined average regions, they are not taken into account for the design in RF-LAMINATE Surfaces. Which setting did I miss here?

New FAQ 004275 EN-US

#### Answer

To consider average regions when designing in RF-LAMINATE, they must always be activated in the detail settings of the add-on module. See Figure 01 with the detailed settings in RF-LAMINATE for this.
• ### In a model with surface supports, the calculation does not converge or the result has very large deformations and implausible stresses. What are the reasons for this?

New FAQ 004252 EN-US

#### Answer

The definition of surface supports should be as realistic as possible. Experience shows that the equation solver works most effectively with this. To simplify matters, degrees of freedom are often defined as 'fixed'. However, this can have a big impact on the overall stiffness matrix and cause numerical problems (see Figure 01).

It is better to work with springs in order to avoid the numerical problems. It is often sufficient to define very stiff springs (see Figure 02). The same applies to the foundation perpendicular to the surface. You can find more information in [1] and in the links below this FAQ.

• ### In spite of having defined smooth ranges, they are not considered in the design in RF-STEEL Surfaces. What setting have I missed here?

FAQ 004229 EN-US

#### Answer

So that smooth ranges are taken into account in the design in RF-STEEL surfaces, they must always be activated in the detail settings of the add-on module. See Figure 01 with the detail settings in RF-STEEL Surfaces.
• ### I have a surface with complicated geometry and would like to know the surface area. Does RFEM display the surface area anywhere?

FAQ 004207 EN-US

#### Answer

You can query the surface area using the shortcut menu.

Right-click on any surface of the entered structure. In the shortcut menu, you can find the entry 'Centroid and Info...'

In the dialog box that appears, it is possible to find the available information on this surface.

There you can find e.g. the surface area or the weight.
Optionally, a node can be created in the centroid of theselected surface. A multiple selection of surfaces is also possible.

• ### What is the meaning of 'Shear Failure in Glued Contact Surface' in the details of the RF-LAMINATE add-on module?

New FAQ 004206 EN-US

#### Answer

In the case of cross laminated timber panels not glued to the narrow sides and a wall-like structural behaviour, the torsion stress in the glued joints is often decisive. This design is performed according to the explanations in the literature reference below according to the following equation.

$\eta_x=\frac{\tau_{tor,x}}{f_{v,tor}}+\frac{\tau_x+\tau_{xz}}{f_R}=\frac{\displaystyle\frac{3\ast n_{xy}}{b(n-1)}}{f_{v,tor}}+\frac{{\displaystyle\frac{\frac{\partial n_x}{\partial x}}{n-1}}+\tau_{xz}}{f_R}\leq1$

Values:
• b board width
• n number of board layers
• nxy shear in pane plane
• $\frac{\partial n_x}{\partial x}$ shear of board layers
• $\tau_{xz}$ shear in thickness direction
• fR rolling shear strength
• fv,tor torsion shear resistance
For the y-direction, the design is analogous but with the values for the y-direction.
• ### When splitting a member into surfaces, I get an instability in the calculation. Why?

FAQ 004202 EN-US

#### Answer

If a member is splitted into surfaces, it is necessary to connect the newly created surfaces with the existing members. This can be done, for example, with a rigid surface (option 'Create Frontal Plates on Both Edges' in the settings, see Image and Video).

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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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