The structural tree: new experimentation with reinforced stone

Abstract

Starting from the reinterpretation of the natural forms that recurs in the consolidated shapes of historical buildings, the research proposes the umbrella vault as isolated selfsupporting cover. The research outcome, defined with the term "structural tree", can be considered as an extreme experimentation of the cooperation possibilities between natural stone and steel reinforcement. The idea arises from the observation of fan vaults in which appears an isolated support: its static behaviour works, of course, because of the presence of an opposite structural portion. In this case, on the contrary, there are no lateral supports but it arises as a self-referential element, while the task of restoring the structural balance is left to the upper reinforcement that allows a free composition of the "tree" without static constraints. The study is based on a formal research that combines the possibility to create serial and repeatable compositions with the achievement of an ideal static equilibrium configuration of the stone structure that considers the collaboration between the voussoirs and the upper reinforcement. The steel structure is not assumed as a pre-tensioned reinforcement, like in the other prototypes, but as a passive reinforcement to recreate the compression condition of the arch, usually generated by the opposing forces belonging to the two symmetrical halves.