Storia dell'ingegneria strutturale italiana. Ascesa e declino

In the 1950s and 1960s Italian engineering got the international attention with a number of extremely original structural works. In the transition from the reconstruction to the economic boom, Italy had many chances to build great structures: the reconstruction of thousands destroyed bridges; the so called “Autostrada del Sole” (Motorway of the Sun); the Games of the XVII Olympiad in Rome in 1960; the 100th anniversary of Italian unification in Turin in 1961; hangars and stations in international airports; the Italian-style skyscrapers in Milan and Rome. A real School of Structural Engineering took shape from this creative rush. How the paradox of a country that lagged far behind others in terms of technology but, at the same time, generated a particularly advanced engineering could be explained? In order to answer this question we have to retrace our steps. The success of the Italian Style engineering, in fact, is the climax of a long experimenting process that started with the advent of reinforced concrete in the early 20th century and continued uninterrupted during the autarchy period and the Second World War. The Italian School was univocally based on reinforced concrete, a material that has completely replaced metal structures since the beginning of the century. It was firstly used for great structures in the scientific sector, thanks to Camillo Guidi and Silvio Canevazzi first and Arturo Danusso and Gustavo Colonnetti later on. These two closely cooperated with the most important Italian agents for the Hennebique system and then with a particularly productive generation of design engineers. The collaboration between Danusso and Nervi gave birth to the Italian Style applied to the slender vault - this structural scheme, thanks to its shape-dependent resistance is able to bypass the weakness represented by the low concrete tensile strength. In Italy, Danusso, theorist and designer, pioneered testing on large scale models to calculate and assess structures. He created the Prove modelli e costruzioni, Model and construction tests, lab at the Polytechnic of Milan in 1931 and Ismes in Bergamo in 1951. Along this pathway, he met Nervi in the early 1930s. The result of this meeting was the first model (made of celluloid) for the Italian Air Force hangars in Orvieto. In those same years Nervi, with his own building firm, took over a parallel testing to offer a new manufacture method to produce reinforced concrete structures. The “Sistema Nervi” (Nervi System) resulted from the double need to eliminate costly formworks and comply with the very nature of the material and it was based on two brilliant expedients: structural prefabrication and ferrocemento. The system, refined throughout multiple minor experiences, was perfect for large roofs - a slightly corrugated or ribbed surface, an original reinterpretation of the slender vault, then became the typical Nervi’s mark in his late architectural works. Prestressing would then regenerate reinforce concrete structures in those same years. In this case, stress effects were employed to save iron, on one hand, and to “train” concrete to oppose stress actions, on the other. It was another scientist who spread this principle, Colonnetti - thanks to his efforts - first in autarchic Italy, then during his exile in Lausanne, and finally as the president of the CNR (National Research Centre) - the first bridges made of prestressed reinforced concrete could be built between 1949 and 1951. Due to postwar reconstruction and the following boom years, Italian engineering could finally apply the outcomes of processes that had been long tested in the previous years on real buildings. This was the stage in which the Italian School of Engineering started its on-the-job training, and not just with its most famous protagonists’ works, but with the contributions by a whole generation of designers: Nervi, Morandi, Krall, Cestelli Guidi closely followed by younger Zorzi, Musmeci, Carè and Giannelli, Galli and Franciosi. The Autostrada del Sole, with its high number of bridges and viaducts, gathered the several personalities of the Italian School. Prestressed concrete bridges mainly crossed the widest of rivers - the wide concrete arch played a protagonist role on the Appennini Mountains stretch and its construction, divided into a multitude of small parts that small building firms had to deal with, represented an epic and spectacular version of the Made in Italy. In the meanwhile, Nervi’s architectural concept asserted itself as a leading one with the four masterpieces that he designed for the 1960 Rome Olympics, with his Nervi & Bartoli building firm. In those same years Morandi, following his own pathway, developed an absolutely unique architectural style. The passionate and skilful way to use prestressing processes resulted into sophisticated and light versions of the basic structural schemes, to finally get to the cable-stayed beam on a balanced support, not made of concrete but steel. After the bridge over the Maracaibo’s lagoon in Venezuela, the same element was then used in Italy in the Polcevera bridge in Genoa, the Magliana viaducts and the Fiumicino airport hangars in Rome. In the 1960s the international fame of Italian engineering spread worldwide. But right when it peaked, the golden age of Italian engineering came to an abrupt end. This was due to the sudden change of Italian production industry but it was also the effect of the more generalized and far deeper transformation of the structural engineering field. Italian engineer could not find its own way in the new international framework. The generation of Nervi, Morandi, Musmeci, Zorzi, left a legacy of high-quality works but no heirs could go ahead with what had been done till then