Sign convention of shell elements

Hi everybody

I am currently working with concrete shells (modeled from mesh elements). What is however the sign convention of the local forces? For example a positive n_xx is a tension force, a positive m_xx is defined as a moment which causes tension on the top edge of the shell (top edge in positive local z direction)… but how is a positive n_xy defined?

If it is not too much effort, could you please represent the sign convention of the local forces in the same way which displayed on the figure I uploaded with this post?

Thank you very much in advance!

Figure2

Hi @crovati,
the sign-convention for the in-plane shear forces n_xy should be like in your drawing drawing with reference to the local element coordinate system xyz.
– Clemens

Thank you very much Clemens!

Caterina