2810x
000355
2019-08-22

Question

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, 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 the 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.


Author

Mr. Rehm is responsible for developing products for timber structures, and he provides technical support for customers.