Mohr-Coulomb Shell in Abaqus. Help!

Hi,

I am new to Abaqus and I am trying to use it to model some industrial shells. According to some preliminar studies, the material has a mohr-coulomb plastic behaviour. Thus, I wanted to use shell elements, with a mohr-coulomb plastic material, but it seems that it is not possible in Abaqus.

According to the theoretical manual and the user manual (18.3.3-6):

"The Mohr-Coulomb plasticity model can be used with any stress/displacement elements in Abaqus/Standard other than one-dimensional elements (beam and truss elements) or elements for which the assumed stress state is plane stress (plane stress, shell, and membrane elements)."

However, my shells are not in plane stress! I have tried also with some simple tests with clearly out-of-plane stresses and still I get the error "MOHR COULOMB NOT ALLOWED IN PLANE STRESS".

Is it possible to use shell elements in Abaqus in general stress conditions? How?

 Thank you in advance,

Paolo