The Arch of Augustus in Rimini: the internal structure determined with a special tomography

The Arch of Augustus in Rimini, built in 27 B.C., is the oldest Roman arch that has survived until today. In the middle Ages, it was included in the city wall and was used as a city gate, with two round towers built to flank it, and a crenellated cornice built on the top. In 1937 the city walls and neighbouring buildings were demolished and a first restoration of the arch was made. In World War II the arch was damaged by a mine and in 1948 it was restored reconstructing the destroyed masonry; and the cementation of the core in the arch, with 22 drills for a total length of 164 m, was made. In 1997 the arch was subjected to massive strengthening works, and 129 reinforced borings, around 260 cm long, and 37 others borings were made. The availability of the notes taken during the execution of the borings, where the location and direction of the holes and the ma-terial found at each depth were registered, giving massive information on the structure of the inner core in dif-ferent parts and directions. This data gave the possibility to perform a tomographic reconstruction of the struc-ture of the arch, locating the exact thickness of Istrian stone ashlars, of brick masonry and of inner opus cae-menticium, as well as the consistency of cementation of the post-war works. On this basis, a reliable 3D struc-tural model of the arch in its current state, was made.