In Advance Design, after finishing the finite element analysis (FEA), the "**Torsor**" results can be displayed. These results are typical only for vertical planar elements (these are elements created perpendicular on the (XOY) global plane).

In order to understand their significance the concrete wall from **Figure 1** is considered. It is part of a multi-story reinforced concrete structure.

**Figure 1.** Local axis orientation of the analyzed wall

When the finite element calculation is done, the following torsor results are available:

- N (axial force);

- M (bending moment);

- T (shear force).

Torsor values, for the selected static load cases, are obtained by numerical integration of the efforts determined with the finite element method. For the considered example, taking into account the local axis orientation, the torsors for static load cases are calculated in the following manner:

_{xx}dy

Torsor Txy = ∫ F

_{xy}dy

Torsor Tyz = ∫ F

_{xz}dy (this torsor is always perpendicular on the (xy) plane of the wall)

Torsor Mz = ∫ F

_{xx}y dy

Torsor Mf = ∫ M

_{yy}y dy

**Note:** F_{xx}, F_{xy},F_{xz}, M_{yy} are efforts determined in the local axis of the planar element.

For seismic load cases or for load combinations which contain seismic action, the torsors are derived from efforts obtained by modal superposition by the **CQC** rules (Complete Quadratic Combination) or **SRSS** (Square Root of the Sum of the Squares) and subsequently, their numerical integration.

**Figure 2** to **Figure 6** show the torsors Mz, N, Txy, Mf, Tyz for the analyzed wall in a load combination which contains the seismic action. The efforts are determined in the local axis.

Figure 2. Torsor Mz |
Figure 3. Torsor N |
Figure 4. Torsor Txy |

Figure 5. Torsor Mf |
Figure 6. Torsor Tyz |

Torsors left/right are used mainly for coupling beams. More detailed information can be found in the following FAQ: How is a coupling beam modeled?

Torsors/Group are determined when the "**Walls group**" option (**Figure 7**) is active on a system where the cooperating walls were grouped.

**Figure 7.** "Walls group" option

Torsors/Group can also be displayed without activating the option. This can be donein the analysis model by selecting the group of walls which are cooperating and displaying the desired torsor (Figure 8).

**Figure 8.** Torsor NZ/Group

Torsors/Level are determined when the "**Level**" option (**Figure 9**) is active on a system which contains the elements of the respective level. **Figure 10** shows the TX torsor corresponding to ground level.

**Figure 9.** Activating the "Level" option on a system which is containing the elements of the respective level

**Figure 10.** Torsor TX/Level