Effective treatment of complex statical and dynamical load combinations within shakedown analysis of 3D frames

A strategy for an efficient treatment of load combinations is proposed with the aim of making the shakedown analysis an affordable design tool to be used in practical applications. The paper refers to 3D frames subjected to complex combinations of statical and dynamical loads defined according to Eurocode rules. The yield surface of the sections is defined by its support function values associated to presso-flexural mechanisms and it is approximated as Minkowski sum of ellipsoids. An algorithm capable of detecting the significant vertexes of the elastic envelope and suitable for use in the case of response spectrum analyses, is proposed.