Answer:
The RF‑CONCRETE Surfaces add-on module uses the resulting shear force from the basic internal forces vx and vy. The internal force vx corresponds to the shear force distribution in the direction of the local axis x of the surface, and the internal force vy to the shear force distribution in the direction of the local axis y.
The resulting shear force, which is also used in the shear design, is then calculated as:
vEd = √(vx² + vy²)
