# Why is it not possible to define eccentricity in the Z‑direction in my 2D model?

In a 2D model XY with the degrees of freedom (uz/fx/fy), no eccentricity can be defined. The eccentricity usually results in an axial force that is not covered by these degrees of freedom.

You should also be careful when using ribs. In contrast to the 3D model, the effective width also changes the stiffness of the structure.

Therefore, it is generally better to calculate the downstand beam structures in a 3D model.