The plastic limit load design for a perforated structure that contains a large amount of circular holes has attracted much attention from power industry in recent years. Most of the previous analyses have been built on the elastic-perfectly plastic material model with small strain finite element formulation. In the present work, a series of newly developed heterogeneous unit cells based on large strain finite element formulation are applied to consider the effect of work hardening rate and the unit cell size on the computed limit load and failure modes. The results indicate that as the unit cell size increases, the unit cell tends to localize early. Also, we found that for the pre-work hardened materials with a strain-hardening coefficient of less than 0.1, work hardening rate has less effect on the computed limit load, but substantial impact on the calculated local strain magnitude.