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# 8.17 Surfaces - Design Internal Forces

To control the graphical display of the design internal forces, select Surfaces → Design Internal Forces in the Results navigator. Table 4.17 shows the design internal forces of surfaces in numerical form.

The table shows the design internal forces sorted by surfaces. The results are listed in reference to the grid points of each surface.

Grid Point

The numbers of the grid points are listed by surface. For more information about grid points, see Chapter 8.13.

Grid Point Coordinates

Table columns B to D show the coordinates of grid points in the global coordinate system XYZ.

Moments / Axial Forces

The design moments and axial forces shown in this table are based on the approach described in DIN V ENV 1992-1-1, Appendix 2, A 2.8 and A 2.9. Thus, RFEM provides users without access to the design module RF-CONCRETE Surfaces with a tool required for the manual reinforced concrete design. As the RF-CONCRETE Surfaces add-on module uses the method by Baumann, the design internal forces from RFEM are not applied in this add-on module.

### Note

The design moments and axial forces of Table 4.17 must not be combined! As explained in DIN V ENV 1992-1-1, Annex 2.8, the moments exclusively refer to plate reinforcements; the axial forces are based on the design of wall elements described in Annex 2.9.

The design internal forces have the following meanings:

 mx,D+ Design moment in the direction of the local axis x on the positive side of the surface (i.e. side in direction of positive surface axis z) for mx ≤ my and mx ≥ −│mxy│ for mx > my and my ≥ −│mxy│ 0 for mx ≤ my and mx < −│mxy│ for mx > my and my < −│mxy│ my,D+ Design moment in the direction of the local axis y on the positive side of the surface (i.e. side in direction of positive surface axis z) for mx ≤ my and mx ≥ −│mxy│ for mx > my and my ≥ −│mxy│ for mx ≤ my and mx < −│mxy│ 0 for mx > my and mx < −│mxy│ mc,D+ Design moment for concrete stress design on the positive side of the surface for mx ≤ my and mx ≥ −│mxy│ for mx > my and my ≥ −│mxy│ for mx ≤ my and mx < −│mxy│ for mx > my and mx < −│mxy│ mx,D− Design moment in the direction of the axis x on the negative side of the surface for mx ≤ my and my ≤ │mxy│ for mx > my and mx ≤ │mxy│ for mx ≤ my and my > │mxy│ 0 for mx > my and mx > │mxy│ my,D− Design moment in the direction of the axis y on the negative side of the surface for mx ≤ my and my ≤ │mxy│ for mx > my and mx ≤ │mxy│ 0 for mx ≤ my and my > │mxy│ for mx > my and mx > │mxy│ mc,D− Design moment for concrete stress design on the negative side of the surface for mx ≤ my and my ≤ │mxy│ for mx > my and mx ≤ │mxy│ for mx ≤ my and my > │mxy│ for mx > my and mx > │mxy│ nx,D Design force in direction of the local axis x for nx ≤ ny and nx ≥ −│nxy│ for nx > ny and ny ≥ −│nxy│ 0 for nx ≤ ny and nx < −│nxy│ for nx > ny and ny < −│nxy│ ny,D Design force in direction of the local axis y for nx ≤ ny and nx ≥ −│nxy│ for nx > ny and ny ≥ −│nxy│ for nx ≤ ny and nx < −│nxy│ 0 for nx > ny and ny < −│nxy│ nc,D Design force for concrete stress design for nx ≤ ny and nx ≥ −│nxy│ for nx > ny and ny ≥ −│nxy│ for nx ≤ ny and nx < −│nxy│ for nx > ny and ny < −│nxy│