From Art to Science of Construction: the Permanence of Proportional Rules in the “Strange Case” of the 19th Century Ponte Taro Bridge (Parma, Italy)

The bridge commissioned by Maria Luigia to Eng. Antonio Cocconcelli and built between 1816 and 1821 over the Taro River (near Parma, Northern Italy), is a very important monument, both from a cultural and strategic point of view. This 20 arches masonry bridge reaches the length of nearly 600 meters and constitutes a very interesting case study, not only for the technical and structural issues related to its restoration and use (with increased traffic loads) but also for the role that geometry played in its history and stability. In this paper, a compared analysis on the historical ‘proportional theory’ and the constructive features of this ancient bridge is proposed with the final aim to show the importance of recovering “empiricism” in dealing with ancient monuments. Thanks to a high precision survey the realized structure has been compared to the original project, in order to detect the deformations suffered by the structure in time, thus applying the “historical monitoring” procedure to the monument. Hence, starting from the dimensional theory, a static analysis of the bridge is proposed by means of Mery’s graphic method, in order to investigate the structural safety level of the original project, also considering the current load conditions. A comparison with the static results obtained by means of limit analysis, finally shows the validity of ancient proportional theory, which can constitute a first qualitative method for structural validation of ancient masonry structures.