Progettazione a meccanismo controllato di telai in C.A.

Abstract

The Theory oj Plastic Mechanism Control (TPMC), based on the application oj the kinematic theorem oj the plastic collapse, has been developed in the nineties with rejerence to moment-resisting jrames (MRFs) and progressively extended to several steel structural typologies, commonly adopted as seismic-resistant structural system. The aim oj this PhD thesis is the study oj a simple procedure to design moment resisting concrete jrames. This methodology allows to dejine structures having a smart behaviour when subjected to seismic excitation. Infact, the structure develops the maximum number oj dissipative zones by means oj a particular collapse mechanism: the global one. In particular, the outcome oj the theory is the evaluation oj the sum oj the plastic moments oj the columns required, at each storey, to prevent undesiredjailure modes such as sojt-storey mechanism. In the proposed method the second-order effects, due to vertical loads, can play an important rale in the seismic design oj reinforced concrete jrames; they can be taken into account by mean the mechanism equilibrium curve oj the considered collapse mechanism. To complete the study, is important to consider a comparison between the design oj a reinjorced concrete jrame according code rules i.e. adopting the hierarchy criteria and the same frame designed by the Theory oj Plastic Mechanism Contro!. The TPMC is a more sophisticated design procedure because it works in jull compliance with codes recommendations considering that it respects the hierarchy criteria. These last, in jact, are jundamental to avo id dangerous collapse mechanisms such as "sojt-storey" mechanism but they are not sufficient to guarantee the exploitation oj the maximum dissipation capacity oj the frame To validate the TPMC design procedure several practical applications with reference to the design of a multi-storey frame are presented. In addition, both push-over analyses and non.-linear dynamic analyses have been made to 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. Conversely, beam-column hierarchy criterion, commonly suggested by seismic codes, appears only as a very rough approximation when compared to the TPMC and its theoretical background. During the study has been realized the implementation of a graphical interface for the design of reinforced concrete frames. The program works as a pre- and post- processor of a routine calculation for the design of frames with kinematic theorem of plastic collapse. The aim oJ this software is give the possibility to design according to TPMC me tho do logy, through the use of a technological instrument, simple to use from all types of users, even not IT experts. [edited by author]