RFEM – Online Manual

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RFEM – Online Manual

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8.1 Nodes - Support Forces

With the entries under Support Reactions in the Results navigator, you can control, which components are graphically displayed in the work window. They can be related to the local axes of rotated supports or to the global axis system XYZ. Table 4.1 shows the support forces and moments in numerical form.

If the structure is a 2D model, RFEM only displays the table columns of support forces and moments that are relevant for a planar structural system.

Figure 8.2 Results navigator: Support Reactions → Nodal Supports
Figure 8.3 Table 4.1 Nodes - Support Forces

To display the support reactions of a particular load case, select the load case from the list in the main toolbar or the toolbar of the table.

Support Forces P X / P Y / P Z

The support forces are listed in three table columns where they are sorted by nodes. Usually, the forces refer to the axes X, Y, and Z of the global coordinate system. To display the forces related to the local support axes X', Y', and Z' (rotated supports) in the graphic as well as in the table, go to the Results navigator and use Support Reactions → Nodal Supports → Local.

Nodes with support rotations are marked by an asterisk (*) as shown in Figure 8.3. Forces are output in relation to the selected axis system. In the last table column, the support's rotation angle is indicated.

The table shows the forces that are introduced into the support. Thus, with regard to signs, the table does not show the reaction forces on the part of the support. The signs result from the direction of the global axes. If the global axis Z is directed downwards, the load case self-weight, for example, results in a positive support force PZ and a wind load against the global axis X results in a negative support force PX. Thus, the support forces shown in the table represent the foundation loads.

Conversely, the green vectors displayed in the graphic show the reaction forces on the part of the supports. The components of the support reactions are visualized by the size and direction of the vectors.

You can display the signs of support reactions in the work window. Go to Results in the Display navigator and select the corresponding check box.

Figure 8.4 Display navigator: Results → Support Reactions → With sign

The signs in the graphic refer to the global axis system XYZ or the rotated local axis system X'Y'Z'. It is advisable to only display these signs for the introduced forces, as they may otherwise lead to misinterpretations.

Support Moments MX / MY / MZ

The support moments are listed in three table columns where they are sorted by nodes. Usually, the moments refer to the axes X, Y, and Z of the global coordinate system. Use the Results navigator to display the moments related to the local support axes X', Y', and Z' in the graphic as well as in the table.

The table shows the moments that are introduced into the support. With regard to signs, like for support forces, the table does not show the reactions on the part of the support. The signs result from the direction of the global axes. Thus, the support moments shown in the table represent the foundation loads.

In the work window, however, reaction moments on the part of the supports are shown.

Signs for support moments can be displayed in the graphic as well (see Figure 8.4). A positive support moment acts clockwise about the corresponding positive global axis. Similar to the vectors for support forces, vectors are already signed, and indications of value have to be considered independently: The signs indicate the directions of the moments in relation to the global axes.

In the graphic, support moments can be represented as a vector or arc. To change the display type, use the menu option

    • Options → Display Properties → Edit.
Figure 8.5 Display Properties dialog box (section): Nodal moments with arc display

On the left, select the Results → Support Reactions → Nodal Moments Category, then select the Arc display option on the right.

Rotated nodal supports

In the last table column, the rotation angles of rotated nodal supports are indicated (see Figure 8.3). The corresponding nodes are marked by an asterisk (*).

Check sums

For load cases and load combinations, RFEM displays check sums of loads and support reactions at the end of the table. Differences will occur between ∑ Forces and ∑ Loads if the model additionally has line supports and members or surfaces with elastic foundations. Therefore, the ∑ Forces available in Tables 4.3, 4.7, and 4.21 must also be considered for the total summary.

Importing support forces as load

Nodal support forces and moments of another RFEM model can be applied as loads in the current model. Thus, loads can be transferred from floor to floor to analyze 2D floor slabs. This function is described in Chapter 8.3.

Imported nodal support forces are applied as free concentrated loads.

Filtering support forces of result combinations

For result combinations, the default setting of the extreme values shown in the results table can be adjusted by using the menu item

    • Table → View → Result Filter

or the corresponding button in the table toolbar shown on the left.

Figure 8.6 Table Filter dialog box (section)

The check boxes in the Table Filter dialog box control the type and extent of the numerical output for support forces.

Resultants of support reactions

The resultants of support reactions for load cases and load combinations are shown in Table 4.0 Results - Summary for each global direction (see Figure 8.1). Use the Results navigator to also visualize the resultant forces on the model.

Figure 8.7 Results navigator: Support Reactions → Resultant

In addition to the total resultant P, you can display the individual Components that are effective in the model's centroid in an idealized way. Thus, you can check the position and size of the resulting support forces at a glance.