# How can I enter a one-way instead of a two-way slab in RFEM?

It is possible to simulate one-way concrete slabs (e.g. precast slabs) using the 'Orthotropy' of the surfaces.

You can set the stiffness type 'Orthotropic' in the 'Edit Surface' dialog box separately for each surface. See Figure 01.

In the 'Edit Surface Stiffness - Orthotropic' dialog box, you can define the orthotropy type and select, for example, 'Effective Thicknesses.' See Figure 02.

You can then define the effective thickness in the local x- and local y-direction of the corresponding surface in the 'Effective Thickness' tab. Moreover, you also have the possibility in this dialog box to define an effective thickness for the self-weight. See Figure 03.