An optimal design of FE structures with limited ductility

The minimum volume design of elastic perfectly plastic FE structures subjected to quasi-static fixed and cyclic loads is searched in such a way that the structure remains into the elastic field in serviceability conditions, while it is subjected to alternating plasticity under very strong cyclic actions, incremental and instantaneous collapse being prevented. In order to take into account the limited ductility of the material, suitable chosen limits on the plastic deformations related to the initial transient phase and/or to the subsequent steady-state phase are considered for the structure subjected to very strong cyclic actions. A numerical application confirm the theoretical expectations: optimal designs turn out to be quite light, with stiffness and resistance suitable to completely preserve the structure integrity in serviceability conditions, and well as to avoid collapse and to allow a great amount of plastic dissipation production under the action of very strong cyclic loads, plastic deformations being always sufficiently small and remaining null in the entire cycle.