8.6 Members - Internal Forces

To control the graphical display of member internal forces, select the Members check box in the Results navigator. Table 4.6 shows the internal forces and moments in numerical form.

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

To display the internal forces of a particular load case, select the load case from the list in the main toolbar or the toolbar of the tables.

The table lists the internal forces of each member at the following locations:

• Start and end node
• x-locations according to defined member division (see Chapter 4.16)
• Extreme values (Max/Min) of internal forces

To adjust the default setting of the x-locations shown in the results table, use the menu option

• Table → View → Result Filter

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

The check boxes in the Table Filter dialog box control the type and extent of the numerical output (see Chapter 11.5.5).

The diagram graphic for internal forces is based on the result values available in the FE mesh nodes or in the member divisions defined in the Global Calculation Parameters dialog tab of the Calculation Parameters dialog box (see Chapter 7.3.3).

The member internal forces have the following meanings:

Table 8.4 Member internal forces

N	Axial force in member
Vy/Vu	Shear force in direction of local member axis y or u
Vz/Vv	Shear force in direction of local member axis z or v
MT	Torsional moment
My/Mu	Bending moment about axis y or u
Mz/Mv	Bending moment about axis z or v

The local member axes y and z or u and v are the principal axes of the cross-section. Axis y or u represents the "strong" axis, axis z or v the "weak" axis (see Chapter 4.17). When asymmetrical cross-sections are used, you can select if internal forces refer to the principal axes u and v (see graphic above) or to the standard input axes y and z. To set the results display, use the Results navigator as shown on the left. This display setting affects both the graphical results output and the output of results in the tables.

When a nonlinear analysis is performed, internal forces can also be output in relation to the deformed member axis systems. The reference of the internal forces is set in the Options dialog section of the Calculation Parameters dialog box (see Chapter 7.3.1).

To check the member position, use the 3D rendering or the Display navigator where you go to the Model → Members entry and then activate the Member Axis Systems x, y, z.

The display of member axes can also be activated in the member shortcut menu shown on the left.

The local member axis system affects the signs of internal forces.

This internal force regulation only applies if the local z-axis of the members is oriented Downward (option in the general data of the model, see description at Figure 12.28).

However, if the local z-axis is defined Upward, a positive moment M_y causes compressive stresses on the positive member side, a positive moment M_z tensile stresses.

If the table display of extreme values is activated (see Figure 8.22), RFEM shows the maximum positive (Max) and the minimum negative (Min) internal forces for each member. The extreme values are highlighted in bold; the values in the remaining columns of the respective table row represent the internal forces related to the extreme value (also see Chapter 11.5.5).

The final table column provides information about the cross-sections used in the members.

When you look at the results of result combinations, this column is generally titled Corresponding Load Cases (see Figure 8.21). The table shows the numbers of the load cases or load combinations that were used to determine the maximum or minimum internal forces of the respective table row. Load cases classified as Permanent always appear in this table column; Variable load cases are only displayed if their internal forces have an unfavorable effect on the result (see Chapter 5.6).

At the same time, the table is extended by a third column C. It allows you to read the maximum positive (Max) and the minimum negative (Min) values at the end of the internal force list of a member.

The amount of data in the result combination tables can be reduced by using specific filter functions available in the Table Filter dialog box (see Figure 8.22). To open the dialog box, use the menu entry

• Table → View → Result Filter

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