1 December 2017

FAQ 001101 EN

Robert Vogl

Calculation

RFEM

RSTAB

In my L‑section, there is no My or Mz moment when rotating the member by 45°. What is the reason?

Answer

In the case of unsymmetric cross-sections (angles, Z sections), the main axes are inclined. The angle α describes the position of the principal axes u and v in relation to the standard axis system: This is the angle between the member axis y and the "strong" cross-section axis u. It is defined as positive if clockwise.

The resulting bending moments of an unsymmetrical cross-section are displayed in relation to the principal axes by default. Therefore, the descriptions Mu and Mv appear in the graphic and in the table. If you want to display the values of the moments related to the member axes y or z, the corresponding setting must be made in the Results navigator (see Figure 01). The internal forces My and Mz are then displayed in the graphic and in the table.

The display of the principal axes can be activated in the Display navigator by selecting "Member Axis Systems x,u,v" (see Figure 02).

Keywords

L-section Unsymmetric cross-section Principal axis Member axis Axis system Bending moment Angle

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RFEM 5.xx

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Structural engineering software for finite element analysis (FEA) of planar and spatial structural systems consisting of plates, walls, shells, members (beams), solids and contact elements

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RSTAB 8.xx

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