Castelli di acciaio. Il sistema tubo-giunto di Ferdinando Innocenti

In August 1935, an unconventional scaffold was used in the construction of a cast-in place, reinforced concrete arch bridge spanning 50 m across the Orba river. That was the first steel tube scaffold ever built in Italy. It had been designed and constructed by Fratelli Innocenti. The company owner was Ferdinando Innocenti, who in 1934 had invented a revolutionary metal tube uniting device, which is still among the best products manufactured in Italy. The device featured a quickly assembled, portable and reusable system consisting of a clamping bolt with a T-shape head and a hinge. The novel Innocenti system was more cost-effective than traditional timber framing. For this reason, it was to be used, in the Fifties, in the construction of some major bridges connecting the Autostrada del Sole, and later in the realization of various masterpieces of Italian engineering in the boom years. In the Thirties, the Innocenti system was applied to reinforced concrete construction projects, to set up imposing, temporary works to suit the needs for Fascist propaganda, and also for military use. In post-war years, following the establishment of a new company called Ponteggi Tubolari Dalmine Innocenti, the pipe joint system was used in the construction of awe-inspiring, dismountable and portable steel tube scaffolds designed to support viaducts connecting the new motorways. In 1958, the transfer of the scaffold to be applied to the construction of the twin arch bridge across the Aglio river along the Autostrada del Sole was a pioneering technology performance. RAI, Italy’s public broadcasting company, covered the entire event live, and a documentary film would be produced, which represented Italy at the 1960 Locarno Film Festival. During the same months, even Pier Luigi Nervi used the pipe joint system to combine the precast and cast-in place components of his Palasport domes. On October 24, 1959, one of the high towers Ponteggi had erected to support the prestressed girders of the Lora bridge collapsed. As a result, the popularity of the steel castle suddenly dimmed. In order to investigate on the causes of the structural failure, Ponteggi requested ISMES in Bergamo to carry out a series of model-based tests. Between 1961 and 1962, the pipe joint system was used in the construction of a bridge spanning 235 m across the Fiumarella river in Catanzaro and of other viaducts connecting the Autostrada del Sole in the Florence-Rome. However, no word was spread about those works. In 1965, the Innocenti system was used in the last daring work carried out by Ponteggi Tubolari Dalmine Innocenti in Europe: the construction of the 275 m span arch bridge across the Breguenzer River in Austria. That anticipated also the end of the cast-in place, reinforced concrete arch era and the dissolution of the distinguishing features of the Italian construction site that had been represented by Ferdinando Innocenti’s creation