As we can see, the tangential forces are produced only in a certain closed area that is determined by an effective width (tef) and not in the entire section, thus leaving the internal part of the piece free of these tangential stresses. The EC-2 tells us how to calculate the tangential stresses produced by the torsion in this concrete area delimited by tef (effective width). All the formulation used can be found below, in the section "Formulation of torsional resistance". These stresses must be compared with the concrete tensile strength resistance of concrete, fctd.

- Longitudinal efforts: As we see in the strut and tie model, these tangential stresses move along the piece in the form of an "spiral". It shows how tensile ties are generated that represent the additional longitudinal reinforcement to be added to the beam and the compressed struts in the concrete that form a theta angle with the ties. This angle must be the same as the one used in the shear calculation, with the same limitations of it. The calculated horizontal reinforcement must be evenly distributed in the perimeter of the concrete considered in the calculation (tef explained above).

- Torsion-shear interaction: As we have mentioned previously, the shear and the torsion are present on the concrete at the same time. Therefore, we must check that the tangential stresses in the concrete due to both phenomena do not exceed the tensile strength of the concrete and that the compression strut also resists the sum of the compressions due to both phenomena. The EC-2 gives us a formula to consider this interaction for both cases, the tangential stresses and for the struts in compression. It also recommends a minimum reinforcement to be considered in the cases when, after taking into account the interaction, the concrete resists the interaction of both phenomena. In case of not resisting, we need to calculate the required shear reinforcement as explained below. However, if the compressed strut does not resist, the only solution will be either to modify the geometry or to increase the compressive strength of our concrete.

- Torsion reinforcement: If the concrete resistance is less than the applied tangential forces (do not forget the interaction with the shear), we must add torsional reinforcement. To calculate the torsional reinforcement, we can calculate an equivalent shear force on each face of our piece produced by the torsion. As we know the tangential stresses in the concrete due to the torsion, we can calculate the shear force on each side multiplying these stresses by the effective width where they are produced (tef) and by zi (the width / height of the piece minus tef). With this calculated shear force we can apply the formula of the shear reinforcement of the EC-2 to calculate the reinforcement needed. We should not forget that this reinforcement (torsion one) must be added to that produced by the shear force. Do not forget either that this reinforcement for the torsion has been calculated for each face, and it must be placed in the 4 faces of our section.

The torsional reinforcement must be placed in the form of closed stirrups. It is important that they are closed to properly resist the torsion.