Compression test

Hi all, I have to simulate a compression test of a structure between two rigid plates and i have some questions.
Is it worth considering plates and structures as an unique component or a better solution is to create different component, with different properties (high E module for rigid for plates)? 
 Also when the upper plate comes down, at the interface between plate and structure, structure could present a horizontally displacement, caused by deformation. How I cold simulate this type of contact?

Thank you all.

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