… using equilibrium in a specific cross-section

Fig. 24 Figure 6.40 Hartsuijker and Welleman (2007)

To find the torsion section forces in a certain cross-section a free-body diagram has to be drawn in which the structure is cut at the point of interest. Following, the forces can be solved using the equilibrium of a body. This is treated in chapter 10.1.3 of the book Engineering Mechanics Volume 1 (Hartsuijker and Welleman, 2006). Typically, the sign of section forces is indicated with deformation signs. A torsional moment is either produced by a moment in the xy-plane, or a shear force excentric to the Shear force centre.