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Frequently Asked Questions (FAQ)
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AnswerThe reason for the occurrence of a bending moment in the oblique and straight bar is that the middle post has a certain flexibility due to its finite rigidity. Thus, compression takes place at the middle support, so that the deformation of the middle support also affects the right-hand latch. Because the right-hand latch is additionally held on a movable support, a forced moment arises at this point.One recognizes it above all by the respective deformations. See alsoThe calculation by means of RFEM results in minimum bending moments, which however are not taken into account in the manual calculation.
Designs in our module RF-/JOINTS Steel - Rigid are based on the assumptions and regulations of the standard EN 1993‑1‑8. Here, bending from the main beam plane is not considered.
In RFEM, it is possible to model any rigid joint. All internal forces can then be taken into account.
In the case of unsymmetric cross-sections (angles, Z-sections), main axes are inclined. The main axis angle α describes the location of the main axes relative to the standard main axis system: this is the angle between the axis y and the axis u. It is defined as positive if clockwise.
If a bending moment at an unsymmetric cross-section is determined, the designation of the bending moment changes to Mu and Mv. These moments also relate to the main axes of the cross-section. If the axes u or v run parallel to the load direction, the corresponding internal force Mu or Mv is omitted.
The position of member axes can be activated in the Display naigator under "Member Axis Systems u,v,w."
The bending moment My is positive if tensile stresses occur at the positive member face (in the direction of the z axis). Mz is positive if compressive stresses occur at the positive member face (in the direction of the y axis).
The sign definition for torsional moments, axial forces, and shear forces conforms to the usual conventions: the internal forces are positive if they act in the positive direction at the positive face.
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