Nervi’s Isostatic Lines’ Inspired Floor Slabs. Beyond the Archetypal Gatti Woolen Mill in Rome

In 1949 the construction company Nervi & Bartoli patented in Italy a construction system for two-dimensional structures with ribs bent in accordance with isostatic lines of bending moments or normal stresses, invented by an engineer from its staff: Aldo Arcangeli. In the years to come “isostatic lines” ribbed slab would become one of the main and distinctive archetypes used by Pier Luigi Nervi throughout the world. This is a cast-in-place reinforced concrete ribbed slab combining static efficiency with aesthetic and spatial qualities. The paper will present different case-studies, demonstrating (with a trans-disciplinary approach) how and when aesthetic, static and constructive issues overcome a rigorous mathematical morphogenesis. Case studies will show how the different patterns of the ribs are influenced both by structural instances (e.g. geometry, loads and constraints) and by the specificities imposed by each design and building site (e.g. use, craftmanship, economy, and replicability).