The northern arch of the Augustus Bridge in Narni.

The Augustus Bridge is a monumental bridge viaduct on the river Nera, north of the town of Narni, built in Roman times and attributed to the reorganization of the Via Flaminia made by Augustus (27 BC). The bridge is made up of four arches, of which only the first survives to the south, has always been a source of admiration for the size and the shape and has been the subject of technical studies and artistic representations. In recent times it has been the subject of some laser surveys and of various structural models, also via finite elements, moreover, also following some seismic events, works have been made to consolidate the surviving parts. Despite the various studies, due to the changes that have taken place over the centuries, both due to natural collapses and due to degradation from anthropic actions, there are still many questions that have not received a precise answer: the slope with the exact dimensions for the arches, the shape of the access routes, the origin of the materials, the absence of breakwaters, the diversity of the shape of the remaining piers and arches. In the present work, the authors, as a complement to papers written in the last years, have focused on the appearance of the northern arch of the bridge, which has a particular ribbed shape, indicated by various authors to be similar in some respects to the roofing vault of the temple of Diana in Nimes, and after having sought its diffusion in other Roman contexts, they also studied its structural behavior through a series of finite element models.