PSI - Issue 44

Michele Frizzarin et al. / Procedia Structural Integrity 44 (2023) 745–749 Michele Frizzarin et al./ Structural Integrity Procedia 00 (2022) 000–000

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1. Introduction The rapid growth of socio-economic activities in many modern urban areas has often been accompanied by a parallel development of the transport network (construction of new infrastructures, junctions, bridges, etc.). Transportation systems, including roads, highways, railways, airports and ports, are a critical component of infrastructure systems. They are necessary for the general public interest, and in particular for commercial, industrial and cultural activities on a national and international scale, and also, after a disastrous event, to facilitate the transport of medical rescue teams, the transfer of injured persons to hospitals and basic necessities. In Italy, most of the bridges, viaducts and tunnels that we cross date back to the period of the post-war economic boom. Over the years, works of considerable engineering level have been carried out, such as to make Italian infrastructure engineering recognized as one of the most advanced in the world. For example, Italy has one of the most complex infrastructural networks in the world: it is second only to Japan for km of tunnels (60% of all European tunnels are in Italy); in the network of main roads of about 180,000 km (excluding provincial and municipal roads, which are most of them) there are about 30,000 bridges and 15,000 tunnels, with an incidence of infrastructural works per km traveled among the highest in the world. To this must be added a marked vulnerability of the territory, both from a hydrogeological and seismic point of view. Today, technicians are now fully aware that the materials used for construction have a limited useful life, which can vary greatly depending on the quality of the material itself, but also on the environmental conditions in which the structure is immersed. There is no doubt, however, that bridges and tunnels built more than 50 years ago, even if designed following the dictates of the legislation of the time, today may present levels of performance that are no longer adequate, both for the degradation of materials and for the evolution of the technical legislation. 2. The regulatory evolution of loads for road bridges The technical legislation on civil constructions has undergone, in Italy as in other developed countries, a considerable evolution over the years, the result of increasingly in-depth scientific knowledge as well as an evolution of the concepts of safety and performance. Regarding road bridges, most of the past regulations defined the traffic loads to be applied for the calculation of the actions. Since the dawn of the first technical regulations, the need arose from the necessity to define loads not in use in civil constructions; as regards the other calculation rules, the regulations have often referred to the methods used for the construction of buildings. Starting from the first half of the last century, the following regulations can be identified: • Decreto Ministeriale del 02/08/1980 n. 308; • Decreto Ministeriale del 04/05/1990 n. 24; • Decreto Ministeriale del 14/01/2008 (Norme Tecniche per le Costruzioni NTC2008) e Circolare 02/02/2009 n. 617; • Decreto Ministeriale del 17/01/2018 (Nuove Norme Tecniche per le Costruzioni NTC2018) e Circolare 21/02/2019 n. 7; • Linee Guida per la classificazione e gestione del rischio, la valutazione della sicurezza ed il monitoraggio dei ponti esistenti, approvata dal CSLP il 06/05/2020. Before 1933, it was usually up to the design engineer to define the loads to be applied to the bridges, usually based on the weights of real vehicles (civil and military). • Normale N. 8 del 15/09/1933 del Ministero dei LLPP ; • Normale N. 6018 del 09/06/1945 del Ministero dei LLPP; • Circolare N. 820 del 15/03/1952 della Direzione Generale ANAS; • Circolare N. 384 del 14/02/1962 del Ministero dei LLPP;