Principal stresses

Hello,
Primarily I want to display my principal stresses lines visually. My geometry should be a solid concrete slab. The supports are located at the edges and the slab is to be loaded with a surface load.
I model the slab as a rectangle. I create a mesh from this and than a shell from it.
I connect the points of this mesh with the ‘Line Results on Shells’ component. But both the output Lines 1 and 2 show that the output is empty.

I can’t see where I’m making a mistake, maybe someone will find it in the file. I would be very grateful for any help!

C25-slab.gh (38.2 KB)

Hi, you most likely need to set the LayPos to -1 (bottom of slab) or +1 (top of slab)