A method is presented by which elastoplastic constitutive relations for the solid material equivalent to a perforated plate can be obtained, by performing numerical experiments employing the finite element method. The method is applied to a plate of elastic‐perfectly plastic material, perforated in an equilateral triangular penetration pattern of circular holes. The following situations are considered: plane stress, as existing in thin plates under in‐plane loading, generalized plane strain, which approximates the behaviour of thick plates subjected to in‐plane loading and the plate bending condition. First results have been obtained for the plane stress situation. These results show that, for the case of monotonic loading, the elastoplastic behaviour is nearly isotropic in the plane of the plate, whereas under cyclic loading below the limit load, the equivalent solid material exhibits distortional hardening.