Dynamic Elasto-Plastic Response of Rigid Frames

The procedure for determining the elastic response of structures to transient loads in terms of the elastic normal modes is well known. Assuming ideal plasticity, Bleich and Salvadori recently proposed a method for obtaining the response beyond the elastic range in terms of elasto-plastic normal modes. They applied the method to free-free beams acted on by impulsive loads. In this paper, the method of Bleich and Salvadori is applied in general to two hinged and fixed rigid frames acted upon by a time dependent concentrated force at the knee and in particular to a two hinged frame (for which the elastic normal modes are known) and a linearly decaying forcing function.