Minimum web thickness for torsional stress

As a sample, we have shown the web thickness to be taken for torsional stress. 

According to Eurocode1992-1-1:2004 Tef,i = A / u, where A is total area (including hollows) and u is the external perimeter. Eurocode says that Tef,i can't be less than real wall thickness anyway. A PSC section can have several wall thickness (outer webs, inner webs, upper slabs...), those are a collection we name as Ti

In fact, Midas Civil has a parameter where user can define this minimum thickness, in Section Properties > Web Thick. > for Torsion, Tmin.

So, Tef,i should be = min[(A/u), Tmin, Ti].

The torsional thickness shall be taken as the web width perpendicular to the inclination and not the horizontal one as shown below:

Hope this helps.