Stone reciprocal structures: suggestions from ancient Greece

This contribution aims at developing a complex multi-disciplinary research topic, the study of stone reciprocal structures from a geometrical and structural point of view. The starting point of this research is the fascination exerted by some mysterious objects belonging to the architecture of ancient Greece, i.e., fragments of marble tiles belonging to the roof of the tholos of Athena Pronaia in Delphi, dated back to the first decades of the 4th century BC. According to Vitruvius (De Architectura), it was one of the most important architectures of the classical period, probably designed by the architect Theodoro of Phocaea. Made of marble coming from Attica, with twenty columns of Doric order on the outside, this temple was considered one of the architectural wonders of the world for the algebraic complexity of the geometrical structure, matched in detail and perfection by its decoration. Despite the number of studies on this sanctuary, the poor state of preservation and lack of original material did not allow scholars to perform concluding research on its original configuration, with reference to the reconstruction of the roof. Aware of the various hypotheses formulated by the archaeologists, some of which are particularly interesting, our contribution intends to serve as food for thought by offering an original perspective. More specifically, the goal is not to solve the problem, but to explore the unprecedented possibility that fragments of marble tiles are structural elements. According to this hypothesis, the tiles in question would form a reciprocal stone structure, resulting in an ancient example of stereotomy, i.e., a structure in which the shape of the blocks allows for the definition of a system subject to compressive stresses. Within this context, this contribution is the first step of a research project, aimed at studying different assemblages of marble tiles, by considering that the geometry of the single block strongly depends on the configuration of the entire vault and on its structural response.