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• ### When displaying the result diagrams on a member (the "rib" type), there is the option to display the internal force VL. What is this value and how is it calculated?

New

FAQ 004340 EN-US

The force VL is the longitudinal shear force between the top surface and the member. It is calculated as an integrated shear flow between the plate and the member at a particular point on the member.

For the simplified example provided here, the resulting cross-section values for the integration width of 10 cm are as follows:

• $I_y=\frac{b\times h^3}{12}=\frac{10 cm\times20 cm^3}{12}=6,666.67 cm^4$
• $S_y=h_1\times b\times((h-e_z)-\frac{h_2}2)=10 cm\times10 cm\times((20 cm-10 cm)-\frac{10 cm}2)=500 cm^3$
• $\tau=V_L=\frac{V_z\times S_y}{I_y\times b}=\frac{5.53 kN\times500 cm^3}{6,666.67 cm^4}=0.415 kN/cm=41.5 kN/m$
The integration width has been set to the total of 10 cm.

Values:
• Iy second moment of area
• Sy statical moment
• h1 height of the upper cross-section part
• h2 height of the lower cross-section part
• ez centroidal distance
• h total height
The values can be adjusted for a T-beam.
• ### Is it possible to use the RF/STEEL AISC module as it is and to specify the internal forces, for example, from another calculation or program?

New

FAQ 004305 EN-US

Unfortunately, this is not possible. The design module can only be used together with the internal forces from RSTAB or RFEM.
• ### Is it possible to use the RF/STEEL EC3  module as it is and to specify the internal forces, for example, from another calculation or program?

New

FAQ 004304 EN-US

Unfortunately, this is not possible. The design module can only be used together with the internal forces from RSTAB or RFEM.
• ### Why do the equivalent stresses of RFEM and RF-STEEL differ from each other, although the same CO is considered?

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?

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 the model, there are two governing internal forces, Vz and My. In the printout report selection, I have only activated these two internal forces with the 'Extreme Values' option. Why are duplicate result lines displayed in the report in 'Members - Internal Forces'?

FAQ 004253 EN-US

In this case, the reason for four result lines (see Fig. 01) is that a minimum and a maximum including the associated remaining internal forces are output for each selected internal force.

• First line: Numerical maximum of Vz (3.54 kN) with corresponding internal forces
• Second line: Numerical minimum of Vz (0 kN) with the corresponding internal forces
• Third line: Numerical maximum of My (0 kNm) with corresponding internal forces
• Fourth line: Numerical minimum of My (-12.37 kNm) with corresponding internal forces

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

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.
• ### Why are imperfections taken into account in RFEM and RSTAB when calculating according to the 1st Order Theory, even though, by definition, no component deformations are considered according to the 1st Order Theory?

FAQ 004193 EN-US

In general, an imperfection describes the Incompleteness of a structure or the deviation from an ideal shape caused by the production. 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 1st Order Theory. It is recommended to manage loads and imperfections in separate load cases. They can be combined in an appropriate way with each other in load combinations. Load cases with pure imperfections have to be categorized as action type 'Imperfection' in the general data for load cases (see Figure 02).
• ### Why do I get much higher design ratios in RF-/STEEL compared to cross-section design in RF-/STEEL EC3?

In the RF-/STEEL add-on module, an equivalent stress design is performed according to von Mises. An elastic stress design (EL-EL) is to be made. In RF-/STEEL EC3, a classification is carried out before the design. If the cross-section is classified as class 1 or class 2, the design is performed against plastic limit internal forces. An EL-PL design is performed. If you do not want to use the plastic load reserves, you can switch the design to EL-EL in the details of the RF-/STEEL EC3 add-on module. The results are then comparable with RF-/STEEL.
• ### Displaying the result values is too inaccurate. Where can I adjust displaying of more result values for the member internal forces?

FAQ 004130 EN-US

In the 'Global Calculation Parameters', there is the setting 'Number of Member Divisions for Result Diagrams'.

By default, this value is preset to '10'.

If members with very different lengths are used in a model, it may happen that the preset value of '10' is too small. This is then reflected, for example, by the fact that the parabolic moment diagram is not displayed correctly for the shorter members.

To avoid this problem, enter a higher value, e.g. '50'.

Thus, a parabolic moment diagram is also displayed on the shorter members.

The length of the sections results from the length of the longest member in the structure divided by the defined number of member divisions. The finer division of members applies to all members of the model.

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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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