Geometry as matrix of construction of Roman stone bridges. The Augustus bridge in Narni

Resumen del trabajo presentado a la 45th Computer Applications and Quantitative Methods in Archaeology Conference, celebrada en Atlanta (USA) del 14 al 16 de marzo de 2017.The roman stone bridges, the remains of which are scattered anywhere in romanized territories, are a concrete testimony of the technical level achieved by Romans in the fine art of construction. Many of these, especially if for infrastructure, have considerable size. They have been realized in different orographic conditions and with local materials often by different mechanical properties. The arc is the most used structural element. There are interesting geometric implications in the subdivision of the blocks and in the respective stone cutting project; this is an aspect that precedes of many centuries the birth of stereotomy. Realization of blocks also has implications in the organization of the construction site and in the management of operations related to the specialization of workforce. Studying the Augustus Bridge in Narni, of which a digital survey was recently done, we have obtained several representative models of the above mentioned problems. It still retains an integral span and pieces of spans; the collapsed central span measured 30 m in diameter, one of the largest in Europe; one span presents a different technique by rings, that poses interesting questions of dating. Processing 3D models, between the current state and the original one, regards also an application of parametric modeling, as transformation of basic geometric elements that, starting from a simple block of stone, have become then the structural blocks of the arc.Peer reviewe