With the design of St. Mary's Cathedral, Nervi, commissioned as structural design consultant by his friend architect Pietro Belluschi, dean of architecture at the Massachusetts Institute of Technology and consulting architect for the local firm McSweeney, Ryan & Lee, did not hesitate to take up the challenge of testing his own experiments on structures for a very innovative work in a highly seismic area.
The project is characterised by its hyperbolic paraboloid dome, reminiscent of those in Kenzo Tange's cathedral in Tokyo but also those studied by Eduardo Catalano, Belluschi's friend and colleague at MIT. Arranged in the shape of a Greek cross, the 42 metre high paraboloids rest on profile arches and triangular sections that bear the load on four sculptural sloping pillars. Reinforced by exposed ribs on the inner face, the paraboloids are built using the usual system adopted by Nervi of prefabricated ferroconcrete tiles, here shaped into triangles, and cast in-situ completion. The result, on the inside, is an elegant triangular weave warped according to the crooked horizontal straight lines of one of the two families of generators of the paraboloids, and spatial curved lines for the ribs that espouse the double-curvature configuration.
Almost as if to emphasise the geometric foundations of the spatial concept, the covering of the dome in travertine slabs is instead marked by the double mesh of crooked straight lines that generates the double-curved surface of the parabolids.
The model experiments conducted at Ismes between 1964 and 1965 are for Nervi the test-bed for his structural intuition. The results, attesting to its validity, would be confirmed by computer verifications on the basis of advanced numerical modelling by Robinson & Associates, who were locally responsible for the executive project, and the Californian auditors.
In the execution phase, however, Nervi's role ends up fading, although he even plans to ship the prefabricated pieces of the dome from Rome to San Francisco.
Between this last attempt to control the construction site and the surprise of seeing the intuitions tested on experimental models verified on the computer, the end of a world almost came. Engineering has become engineering and a family-run firm like Nervi's has little hope of survival, despite its irrepressible international fame. St. Mary's is the swan song not only of the Nervi studio but of an entire season of civil engineering.
