Brunelleschi’s herringbone hidden reciprocal structure and the form finding of its self-supporting bricks

Here we present the progress of a study started from the analysis of the building technology of Filippo Brunelleschi's Dome of Santa Maria del Fiore in Florence [9]. Nowadays, form finding procedure can assume a deeply different meaning from the one usually intended. This case study represents an evidence of it. This ongoing research does not claim to unveil the mystery of the realization of the Dome of Florence Cathedral, but wants to offer a possible interpretation in accordance with that part of researchers, like Salvatore Di Pasquale, who are certain of the existence of a rotational surface contained inside the wall thickness. Starting from this assumption, this study has led to the identification of a self-supporting structure, composed by bricks, arranged in a reciprocal three-dimensional scheme together with a system of mutually supporting ribs [8]. The geometrical aggregation of the bricks constitutes a series of trihedrons arranged in a spatial spiral. These spirals are then connected together by brick walls, perfectly aligned and congruent with the spirals' bricks, so defining the Brunelleschi's herringbone pattern. This form finding procedure can also be applied to domes different from the one of Santa Maria del Fiore: various dimensions and curvature can be covered by a system of trihedrons following a path of three-dimensional spirals.