For a member with an unsymmetric cross-section, the load plane runs through the center of gravity of the cross-section and not through the shear center. Therefore, torsion resistance must occur. Why is there MT = 0 ?

Answer

In RFEM and RSTAB, loads are generally related to the shear center. Therefore, an intentional torsion due to the section geometry (the center of gravity unequal to the shear center) is not considered. The graphic with the system line (=centroidal axis) and the load applied to it can lead to a wrong conclusion.

In order to create the torsion due to a load, which does not act in the shear center, it is thus necessary to apply an additional torsional moment (a load multiplied by the distance to the shear center).

As an alternative, you can perform a calculation in the RF‑/STEEL EC3 Warping Torsion add‑on module. It is possible to apply the load in the center of gravity here.

Keywords

torsion seventh degree of freedom warping torsion shear center

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RFEM Main Program
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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3,540.00 USD
RSTAB Main Program
RSTAB 8.xx

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The structural engineering software for design of frame, beam and truss structures, performing linear and nonlinear calculations of internal forces, deformations, and support reactions

Price of First License
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RFEM Steel and Aluminum Structures
RF-STEEL Warping Torsion 5.xx

Module Extension for RF-STEEL EC3 and RF-STEEL AISC

Warping torsion analysis according to the second-order theory with 7 degrees of freedom

Price of First License
850.00 USD
RSTAB Steel and Aluminum Structures
STEEL Warping Torsion 8.xx

Module Extension for STEEL EC3 and RF-STEEL AISC

Warping torsion analysis according to the second-order theory with 7 degrees of freedom

Price of First License
850.00 USD