Structural lexicon. Expressiveness of steel grids in Italian urban contexts

Introduction of a new technology often involves some degree of friction resulting from the drive towards innovation and the need to develop architecture which is culturally acceptable. This process of lexical codification can be seen in the diffusion of iron and steel constructions in Italy during the mid-19th century. This diffusion is not characterized by a linear development, but consists of several phases and includes a period of resurgence in the 1950s and 60s. A significant phase for its affirmation consists in the acquisition of an architectural language proposed by the Italian Modern Movement. In particular, its lexeme linked to steel construction is the “rationalist grid”, that implies a clear distinction between the exposed frame and the envelope. The pattern of pillars and beams allows an essential design of extroverted structural nodes, following complex geometries that combine commercial profiles and technological components with traditional architectural themes in order to define original relationships with the historical and artistic significance of the surroundings. Influence of the technique, suggested by the international scenario, is balanced by features deeply-rooted in historical urban contexts that affect the design of the details between the steel structure and its envelope. As a consequence some architects rediscover the craftsmanship tradition. This essay aims to trace the sequence of events that led to the definition of the original relationship between steel and architecture, identifying archetypes and developments that take place in the twenty years following the Second World War, a period that represents a phase of “continuity” and “reconsideration” of the modern lexicon.