Erik Kostson
Ansys Employee

See this post for a workflow that an be used to model flexural failure in beams, punching shear in slabs, shear failure in beams,etc.

It has been tested and verified for these type of failures so it should do what you need.
Also generally in these simple bending tests of beams and slabs, the support steel plates can be bonded to the concrete and that is fine - make sure you restrain the correct degrees of freedom on the steel plate - use also enforced displacement on the top plates pushing down and then calculate the reaction force there to get the total force just as shown in the post above.

Thank you