STRENGTHENING OF STONE MASONRY ARCH BRIDGES THREE ...

History
The medieval bridges have projecting piers, triangular in shape, known as cutwaters.
These are found on the upper side with the point towards the stream their purpose being
to protect the pier from the force of the current and from the impact of trees and other
objects borne along by the water. The upper part of these piers at roadway level has
refuges for pedestrians.
The spans varied from five feet in the case of small bridges to twenty feet or more in a
few cases. The first were semicircular with a barrel vault. In the 13th century pointed
arches replaced these arches and groined vaults replaced barrel vaults.
Fig. 1.9 – Poined arch
Here the main weight was taken on ribs of stone. Some bridges have had the ribs cut
away to improve navigation. In others, the ribs have been filled with brick.
Also the equipment used in the construction developed. Mechanisms that allowed to lift
weights, were frequently used in the Antiquity, but in the Medium Age they were
improved, such as the counterbalance and the double pulleys. The cranes were put on
the soil if the work didn't go very high; otherwise they were put on a platform. These
cranes were made in such a way that they being set up and dismounted with the few
men's help.
Leonardo da Vinci Program 12