In this talk I shall discuss the rigorous derivation of a quasistatic evolution model for a thin plate in the framework of Prandtl-Reuss plasticity via Gamma-convergence techniques. The limiting model has a genuinely three-dimensional nature, unless specific data are prescribed. In particular, the stretching and bending components of the stress decouple only in the equilibrium condition, while the whole stress is involved in the stress constraint and in the flow rule. I shall also present an ad hoc notion of stress-strain duality, which allows one to write a strong formulation of the flow rule in the limit problem. This is based on a joint work with Elisa Davoli (Carnegie Mellon University).