Roman bridges, built by ancient Romans, were the first large and lasting bridges built. Roman bridges were built with stone and had the arch as the basic structure (see arch bridge). Most utilized concrete as well, which the Romans were the first to use for bridges.
In the history of civilization, arched masonry bridges represent, from a historical point of view, the most important category for the quantity of achievements and the diffusion in various geographical areas, testify to posterity the design systems adopted by the various peoples, the technologies in use at the time of construction, methods of transport and communication, history and culture and, in any case, always hand down a masterpiece of human creative genius.
The first masonry arch bridges were found in Mesopotamia (around the 4th millennium BC) and later in Egypt and Persia. Also in Greece stone arch bridges were built, generally of modest size and with a single arch.
The Romans were the true masters of the execution of arched bridges, even if their first bridges were made of wood, like the Sublicio Bridge over the Tiber, which, besides guaranteeing the connection with the right bank of the river, constituted a valid element of defense as it could be dismantled in dangerous conditions.
The first stone bridge built by the Romans is the bridge that called Emilio. It underwent numerous destructions and was rebuilt the last time by Gregory XIII in 1575, which wanted to maintain the severity and primitive grandeur. The reconstruction did not have much luck because already in 1598 two arches fell, since then the bridge was called “Broken”. The only arch now surviving is sufficient to give vision of what was the strength and beauty of the bridge.
As with the vault and the dome the Romans were the first to fully realize the potential of arches for bridge construction.
The Roman bridges are characterized by the almost exclusive use of the round arch, probably because this was the simplest form of construction to be made: in fact, for an arch of constant thickness, each stone (constitutive portion of the arch) in stone or in bricks – linked in some way with pozzolanic cement… pozzolana – it is delimited by two concentric circles and two contiguous beams, all coming out from a single center, so that all the segments are equal to each other.
The construction of the vault requires a circular rib (with a radius equal to that of the intrados of the arch), easily constructed and adjustable by the carpenters, on which the individual segments were placed in sequence. The rib could be placed directly on the ground, or fixed on the graft point of the vault; this last solution, useful for saving wood, was widely adopted by the Romans, who for this purpose prepared protrusions at the level of the last horizontal row, on which the ribs were installed.
These techniques remained almost unchanged over the centuries until the introduction of steel tubes.
Presented by Romano Pisciotti
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