The Augustan Bridge at Narni: 3D Modelling and FEM Analysis for Conservation e Restoration

The Augustan Bridge at Narni (27 BCE) is a key point on the Via Flaminia, which connects Rome to Rimini, and represents one of the greatest transit infrastructure realized by the Romans. It's a bridge viaduct and it grows 30 m high over the Nera River, with an arches length of about 160 m. Though having collapsed several times it retains its first arch on the south side, the head joint to the rocks on the northern side and the remains of two piers, one of which collapsed in 1885 in the central section. The second collapsed arch measured approximately 32 m, one of the biggest span of romans arches. The remaining first arch has sustained a horizontal shift that makes it particularly susceptible to seismic events. Following an earthquake in 2000, the surviving arch was subject of restoration works (completed in 2005). A laser scanner survey has been carried out to obtain more extensive metric data and recreate a tridimensional model, useful also for structural analysis. With the 3D FEM models it has been evaluated the structural status of the bridge, at first in its original configuration, with particular focus on the study of the fourth arch due to its characteristic ribbed shape, then in the configuration after the subsidence of the second pier, main cause of the collapse, and at last in the present one of the remaining parts.