La cultura della normativa antisismica e la sua evoluzione.

Il centenario dell’evento sismico che ha interessato lo Stretto è stato colto come occasione di riflessioni sulle attività antisismiche sviluppatesi nell’arco del secolo XX. In particolare il contributo al libro e al convegno ha trattato l’evoluzione della normativa antisismica italiana che origina proprio nel periodo successivo alla calamità che colpì Reggio e Messina. A queste riflessioni se ne aggiungono altre sulle tecniche tradizionali e sulle moderne applicazioni tecnologiche per il loro consolidamento e rinforzo. In particolare sono state evidenziate quelle tipologie di murature armate (con ferro e legno) che spesso sono state adottate nell’area mediterranea e che con la loro reiterazione e permanenza nel tempo assumono caratteri di tradizionalità costruttiva. / The following study wants to underline the evolution of the knowledge and the constructive procedures in relationship to the seismic action and the normative production of the last three/four centuries. It is possible to find out in the ancient framework constructions, in a way alternative to the blocks structures or to the masonry building, a common matrix in the Mediterranean area, developed in the last century, when the elastic framework started to be considered as a valid answer to seismic possibility. Through the examination of the norms, it is possible to track a first phase in which the technical-normative devices come after the events – as the occasion of the seism of Calabria – Sicily and the Abruzzo regions (where the event was influenced by similar cultural context) – with local characteristic and constructive directions. There is a second phase in which the technical-normative set of rules, extended to the whole national territory, including project indications based on the numerical verification, precedes the event with a pre-caution attitude. At the same time, in the development of the reinforced concrete technique it is found a parable that is sorted out among its own technical identity and the application in the field of consolidation of historical and monumental constructions. In this contest, we can witness at first to the one ‘triumphal’ and ‘aggressive’ phase of great successes and expectations – regularly recorded by essays and publications of that time – so to give way to a reflection in which – apart from the positive effects in safety terms – incompatibility and lacks were also recognized, especially in terms of duration. At the same time, with an evident causal connection, a recovery of the structural values of the masonries occurred until, in the actual phase, particular ‘guidelines’ are developed with maximum respect for the existing structures, in the order to preserve their historical and documentary capability and also their ‘material part’. At the same time, the techniques and the cares of the historical construction tradition are also recovered through their employment.