Volte sottili a geometria rigata. Le coperture di Giorgio Baroni per l’Alfa Romeo al Portello e le Fonderie Vanzetti a Milano

At the beginning of 20th century the development of industrial sector gave the opportunity to investigate innovative construction techniques and apply new patents, mainly in the field of reinforced concrete systems. Among these, particular attention should be paid to thin concrete shell structures, firstly studied in Germany and France during twenties. These types of roofs met efficiently the functional needs of industrial buildings, especially for cover the large spans often required. The structural engineer Giorgio Baroni from Milan was the first in Italy to explore the promising opportunities given by thin shells. He patented two systems for hyperbolic paraboloid shell roofs, applying the first of them in 1936 for the Fonderia Vanzetti and in 1939 for the Alfa Romeo factory at Portello, both in Milan. These projects are a clear example of how the experimental research in the field of reinforced concrete structures met the practical needs of the fast-growing industrial sector. The article explains how Baroni’s patent was applied in these two case studies, showing in particular the efficiency of the system to combine structural resistance optimization with saving of construction materials and time. Introducing the construction solutions using in these buildings - today demolished -, the paper retraces the history of two of the first examples of hyperbolic paraboloid thin shell roofs, which became famous after the WW2 with the elegant shapes of Felix Candela, that combine light and structural strength.