Smart and simple design of seismic resistant reinforced concrete frame

In this paper a simple and a more sophisticated design procedure to design moment resisting concrete frames, is presented. This methodology allows to design structures having a smart behaviour when subjected to seismic excitation. In fact, the structure develops the maximum number of dissipative zones by means of a particular collapse mechanism: the global one. The proposed procedure is based on the application of the kinematic theorem of the plastic collapse through the evaluation of the sum of the plastic moments of the columns required, at each storey, to prevent undesired failure modes such as soft-storey mechanism. In this work the authors show how the classical design methodology based on the beam-column hierarchy criterion does not allow to obtain a global mechanism. Beam-column hierarchy criterion, commonly suggested by seismic codes, appears only as a very rough approximation when compared to Theory of Plastic Mechanism Control (TPMC) and its theoretical background. By applying this classic methodology, if a global mechanism is obtained, the design of the column section and its reinforcement are not optimized. In fact, only with the theory already recalled we can obtain the minimum of section columns able to provide the development of a global mechanism. Significant improvements proposed by this approach include, among others, the possibility to account for different amount of reinforcement, not only at the top and bottom of the beam section, but also at the beam ends (left and right). A practical application of the TPMC process for the design of a multi-storey frame is presented, with push-over analysis that investigate the actual collapse mechanism of the designed structure. All the obtained results confirm the capability of the design procedure to achieve a collapse mechanism of global type. The importance of this theory and therefore of the design structures is the possibilities to maximize the energy dissipation capacity and global ductility because all the dissipative zones are involved in the corresponding yielding pattern.