ROMAN BRIDGES
From the earliest times the Romans used used the Pons Sublicius, a wooden bridge resting on piles (heavy beams
driven vertically into the river bed). The stone bridge, however was a relatively late development. In 179BC the
first bridge resting on stone arches, the Pons Aemilius, was built over the Tiber. Wooden bridges continued to be
built by military engineers over lesser rivers. The Flavian emperors (69-96AD) built a wooden bridge over the
Rhine; the emperor Trajan (98-117AD) built a wooden bridge (nearly 400 metres long) over the Danube.
However, both of these had stone arches.
The Pons Milvius or Milvian Bridge, built in 109BC carries the Via Flaminia across the Tiber north of Rome.
Because the road makes a sloping approach to the bridge from both sides, the semi-circular arches are graded, the
highest having a diameter of nearly 20 metres (a humpbacked bridge). The bridge is constructed of unmortared
tufa (solidified volcanic mud) and travertine (limestone) and is held together by the precision of the stone cutting.
Massive piers support the arches and these in turn support the viaduct which has parapets (low protective walls)
on both sides. Upriver, wedge-shaped blocks of masonry are set in front of the piers on the river-bed. When the
flood-water strikes the thin end of the wedge, it is diverted through the adjacent arches, thus relieving the pressure
on the bottom of the piers. Above the cut-waters in the four central piers are barrel vaulted flood-passages which
penetrate the bridge. These relieve the pressure on the upper section of the piers when the water level rises above
the cut-waters. (photo p.152)
Wheeler: “..in the employment of the arch ..the Romans transcended basic utility and became artists”.
“Enough of the Milvian Bridge…has survived …to show the strength and grace of its
original design”.
“it (the Milvian bridge ) displays the early maturity of Roman architectural engineering”.
(p.149)
Bridges were an essential part of the network of roads which, with the growth of the Empire, stretched out from
Rome to the provinces. The use of the arch enabled the Romans to build permanent structures in place of the
earlier wooden bridges and to span wider and more difficult rivers.
A magnificent granite bridge (190 metres long, 6.5 metres wide and 46 metres high at its central point) was built
across the River Tagus at Alcantara in Spain on the Emperor Trajan’s orders in 102AD. The two central arches
are 28 metres in diameter and rest on three narrow piers which are rounded upriver to act as cut-waters. The four
lateral (side) arches are graded into the ravine. Across the centre of the viaduct is an arch dedicated to the emperor
on which are inscribed the words:
“pontem perfeci mansurum in saecula”
“I have built a bridge destined to last throughout the ages”
At one end of the structure stands a small temple which may be the tomb of the builder, Gaius Julius Lacer.
Wheeler: “Let it suffice to say that the bridge itself is a worthy memorial to an honest and forthright
imagination”.
(p.152)
(photo p.153)