ANCIENT TIMBER BRIDGES: NUMERICAL MODELLING OF CONNECTION BEHAVIOUR

In this study structural behaviour of the timber bridge drawn by Leonardo by Vinci in Fol.22 r.a Atlantic Code is analyzed, which can be ascribed to a special timber arch bridge typology. In fact, the arch behavior is obtained by the spatial disposition of rectilinear joists. Based upon Leonardo’s sketch, a geometric model of the military bridge has been made, focusing upon the more interesting technological aspects of this solution: timber beams connections, made resorting to special lashings; timber beams disposition on staggered planes, making a crushproof spatial whole, which behaves like an arch. In such reconstruction, the technological abilities of the epoch in which the bridge would have had to be built are kept in mind. At this aim, the study of the Palladian reconstruction of Caesar’s bridge on the Rhine is particularly meaningful, in relation specifically to connections with lashings. With reference to the disposition of timber beams, it is of great interest the comparison with the bridge built in 2000 at Jinze, in the outskirts of Shanghais, as a reproduction of the ancient "rainbow bridge ", built during the Sung Dynasty (960-1280 A.D.) in the city of Khaifeng. The hypotheses on which the model is based have been verified with opportune schemes of calculation which confirm the validity of the structural conception conceived by Leonardo. Insofar Leonardo’s military bridge constitutes a meaningful step in the evolutionary path of the timber arch bridge made with rectilinear elements, a path which can be considered to start with Train’s bridge on Danube river, and to end with the last great Swiss bridges of the eighteenth century.