Further Information

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• When calculating a connection with the FRAMEmaker Pro add-on module, a message appears indicating that the value is outside the allowable range (Ret. Value: 108, min. Value 100, max. Value 100). What does the mentioned note mean?

New FAQ 003549 EN

The easiest way is to change to the design notes after the calculation or when the note appears in the design notes (see Figure 2). In this case, it is shown that the width of the end plate is not correct. When you change to input window 1.4.2, you quickly recognize in the graphic that it is not within the allowable range.

This can be corrected very quickly by adjusting the horizontal bolt spacings (see Figure 3).
• How do I determine the effective lengths of frame columns in RFEM or RSTAB?

New FAQ 003538 EN

The easiest way to do this is to use the add-on modules RSBUCK (RSTAB) or RF-STABILITY (RFEM).

RSBUCK and RF-STABILITY perform an eigenvalue analysis for the entire model with a certain normal force state. The axial forces are increased iteratively until the critical load case is reached. This stability load is characterized in the numerical calculation by the determinant of the stiffness matrix becoming zero.

If the critical load factor is known, the buckling load and the buckling mode are determined from this. The effective lengths and effective length factors are then determined for this lowest buckling load.

The result shows, depending on the required number of eigenvalues, the critical load factors with the corresponding buckling shapes and, for each member, each buckling shape by a buckling length about the strong and the minor axis.

Since usually every load case has a different normal force state in the elements, a separate corresponding length result for the frame column results for each load situation. The effective length for the design of the respective load situation is the effective length for the buckling length whose buckling mode causes the column to buckle in the corresponding plane.

Since this result may be different for each analysis due to the different load situations, the longest effective length of all calculated analyzes for a design is assumed for all load situations equally for the design - on the safe side.

Example for Manual Calculation and RSBUCK / RF-STABILITY
A 2D frame with a width of 12 m, a height of 7.5 m and pinned supports is provided. The column cross-sections correspond to I240 and the frame latch to an IPE 270. The columns are loaded with two different concentrated loads.

l = 12 m
h = 7.5 m
E = 21,000 kN / cm²
Iy, R = 5790 cm 4
Iy, S = 4250 cm 4

N L = 75 kN
N R = 50 kN

$EI_R=E\ast Iy_R=12159\;kNm^2$
$EI_S=E\ast Iy_S=8925\;kNm^2$

$\nu=\frac2{{\displaystyle\frac{l\ast EI_S}{h\ast EI_R}}+2}=0.63$

The result is the following critical load factor:

$\eta_{Ki}=\frac{6\ast\nu}{(0.216\ast\nu^2+1)\ast(N_L+N_R)}\ast\frac{EI_S}{h^2}=4.4194$

The effective lengths of the frame columns can be determined as follows:

$sk_L=\pi\ast\sqrt{\frac{EI_S}{\eta_{Ki}\ast N_L}}=16.302\;m$

$sk_R=\pi\ast\sqrt{\frac{EI_S}{\eta_{Ki}\ast N_R}}=19.966\;m$

The results from the manual calculation correspond very well with those from RSBUCK or RF-STABILITY.

RSBUCK
$\eta_{Ki}=4.408$
$sk_L=16.322\;m$
$sk_R=19.991\;m$

RF-STABILITY
$\eta_{Ki}=4.408$
$sk_L=16.324\;m$
$sk_R=19.993\;m$
• How many divisions must a member have for the calculation in RFEM so that I get accurate results?

New FAQ 003485 EN

It is not possible to globally answer this question because it depends on the system. There are several divisions to be considered in RFEM.

1. Member divisions for results tables
You can create member divisions for result values by using the menu 'Insert > Model Data > 'Member Divisions'. This division ensures that - e.g. in the RFEM results tables - the internal forces of members can also be displayed at intermediate points. The graphical output remains unaffected.

2. Member divisions
The divisions for the graphical result diagram and the determination of the extreme value can be viewed and influenced in the FE mesh settings (see Figure 1).

For cable, foundation, and tapered members or members with plastic properties, you can specify the number of internal divisions. They lead to a real division of the member by intermediate nodes. However, if a member is arranged on the boundary line of a surface or if the definition line has an FE mesh refinement, the specification has no effect.

Select the 'Activate Internal Member Divisions for Large Deformation Analysis' option to divide also beams by intermediate nodes for the calculation according to large deformation analysis so that these members are calculated with higher accuracy. The number of member divisions is taken over into the input field above.

If using the division even for straight members, which are not integrated into surfaces, FE nodes are generated on all free members and considered for calculations according to the linear static and second-order analysis. The length of the finite elements is either determined by the global target length l FE set in the General dialog section or entered manually.

With the option 'Use Division for Members with Nodes Lying on Them', RFEM generates FE nodes on those locations of the member where end nodes of other members are lying, without having any connection existing between these members.
• I use the load generator 'Convert Area Loads to Member Loads via Cells'. What is the function of the 'Nodes on Virtual Lines' function?

New FAQ 003431 EN

If a cell closed on all sides is detected in the structural model, it can be used for the load application. However, if the desired load range is not completely enclosed by members, the cell is not recognized by the load generator.

With the 'Nodes on Virtual Lines' function, you can define the corner nodes of the load area manually and thus clearly define the cell area. The cell defined in this way can then be selected as usual by using the pick function of the individual cell nodes.

• For the settlement calculation with the RF-SOILIN add-on module, the weight gamma and the specific gravity gamma, sat are interrogated for a certain soil. What do I need the value gamma, sat for, and how does it fit into the calculation?

New FAQ 003422 EN

The value $\gamma,_{sat}$ corresponds to the weight of the saturated soil and can be adjusted, if necessary, in the material parameter settings. If there is groundwater in a layer, the weight of the saturated soil $\gamma,_{sat}$ is automatically reduced from this layer by the weight of groundwater (10kN/m³). Above this layer, the stresses are calculated with the specific weight of the soil.
• How can I change the Standard / National Annex set for the design in add-on modules?

New FAQ 003312 EN

You can usually set the standard and the National Annex in the top right corner of an add‑on module (see Figure 01). In most cases, it is also possible to display the factors of the National Annex and edit them, if necessary (see Figure 02).
• I would like to use a cross-section, which does not exist in the cross-section library of RSTAB and RFEM. Is there a way to get the cross-section?

New FAQ 003306 EN

With the SHAPE-THIN add-on module (thin-walled cross-sections) and SHAPE-MASSIVE add-on module (thick-walled cross-sections), it is possible to model almost any cross-sections which are entered graphically, in tables, or by importing a DXF file.

For SHAPE-THIN and SHAPE-MASSIVE, there is a possibility to create connection to RFEM and RSTAB. Thus, the cross-sections can be imported into RSTAB and RFEM, calculated, and designed in the add-on modules.
• How can I adjust the sheet size for the printout report?

FAQ 003301 EN

By default, DIN A4 is preset as print format in portrait orientation. To adjust these settings, click the "Set Printer" button, which can be found i.a.  in the printout report (see Figure 1).

Editing the page size and the sheet format of individual pages of the printout report is currently not possible.

• Is it possible to output the corresponding internal forces for a maximum or minimum internal force when designing a result combination as an envelope in case of surface internal forces?

FAQ 003293 EN

For members, corresponding internal forces are shown in addition to the maximum values and the minimum values in a result combination. In case of the surface internal forces,  only the maximum/minimum values for each grid point will be shown due to the large amount of data. The corresponding internal forces for a maximum value or minimum value are not shown.

Consequently, RFEM calculates all load cases, load combinations, and result combinations contained in the result combination for the results evaluation and lists the maximum and minimum values accordingly. If you want to have the corresponding internal forces for a result value of the result combination, search for the elements contained in the result combination and compare them with the corresponding value.

If the load case or load combination is found, the corresponding internal forces are also displayed for each grid point of the surface.

For a faster evaluation, you can also use the COM interface.

• Sometimes I get displayed the message 'Some Time-Consuming Display Options are in Use which Slow Down the Rendering Process'. What can I improve?

FAQ 003285 EN

Occasionally, RFEM displays this message when working with relatively large models (see Figure 1). There may be some delays due to time-intensive settings, for example, when displaying the rendering. Thus, the Help Assistant gives information about the settings to be done for reduction of these delays.

Three following options can be selected:

Automatic
The program deactivates the settings such as e.g. rendered view automatically to increase the performance.

Show settings first ...
Settings that have been made that may lead to a slowdown are displayed and can be specifically deactivated (see Figure 2).

No and do not show this message again.
All settings are retained.

However, this message appears only if the 'Rendering Time Optimization' function has been activated using the Wizard in the Program Options (see Figure 3).

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