Diagnosis and preservation of 20th century architectural heritage: from the first thin shell solutions to the iconic structures built by Pier Luigi Nervi and Riccardo Morandi in Turin

Architectural heritage consists of a great variety of buildings and monuments that significantly differ from each other in terms of typology, historic period, construction techniques, and mate-rials. The architectural heritage of the modern movement makes no exception, and its conservation is perhaps one of the most controversial frontiers in the field of architectural preservation. Presently, much of the world’s heritage from this period is unrecognized or undervalued, and therefore, it is at risk and in need of analysis and protection. The recent collapse of Polcevera Viaduct in Genoa has raised strong concerns on the durability of concrete structures conceived at that time. The scientific community has once again underlined the important role played by maintenance and continuous structural health monitoring in avoiding these disastrous events. In order to demonstrate a correct approach to these issues, the paper reports some significant results recently obtained on the structural analysis, seismic assessment and diagnosis of four important 20th century heritage buildings. The first example is the Paraboloide in Casale Monferrato and is intended to track the path, covering most of the specialised tasks involved, from numerical simulations and experimental test design to structural diagnosis, with the consequent definition of the guidelines for possible rehabilitation interventions. The other three analysed cases are different pavilions of the mon-umental complex of Turin Exhibition Center, which represents a milestone in the history of modern engineering and architecture. The main buildings of the Center (Halls B and C) were the subject of several numerical investigations aimed at the seismic assessment and optimal sensor placement. In these roofing systems Pier Luigi Nervi combined innovative prefabrication procedures with ferrocement. For Pavilion V, a hypogeum hall designed by Riccardo Morandi, the authors have conducted extensive numerical analyses and investigations, evidencing its in-herent vulnerability to seismic actions. The possible retrofitting and reuse of this building as a part of the Architecture Faculty Campus is currently under consideration by Politecnico di Torino, which has recently started an extensive campaign of experimental tests.