The ancient Romans were the first civilization to build large, permanent bridges.
History
Following the conquests of Tarquinius Priscus, Etruscan engineers migrated to Rome, bringing with them their knowledge of bridge-building techniques. The oldest bridge in
ancient Rome was the
Pons Sublicius.
It was built in the 6th century BC by
Ancus Marcius over the
Tiber River.
The Romans improved on Etruscan architectural techniques. They developed the
voussoir, stronger
keystones, vaults, and superior arched bridges.
Roman arched bridges were capable of withstanding more stress by dispersing forces across bridges.
Many Roman bridges had semicircular arches, but a few were
Segmental arch, i.e. with an arc of less than 180 degrees.
By the 2nd century BC, the Romans had further refined their bridge-building techniques, using stronger materials such as volcanic ash, Limestone and gypsum. Also, they began to use iron clamps to hold together bridges, constructing midstream arches, and stones to allow for wider vaults.
Between 150 and 50 BC, many stone Roman bridges were built, the Pons Aemilius being the first.
By the 2nd century Roman techniques had declined, and they had been mostly lost by the 4th century.
Construction
Measurements
Roman bridges were much larger than the bridges of other civilizations. They could be anywhere from long. By the time of
Augustus around the turn of the 1st millennium the maximum span of Roman bridges increased from around in 142 BC
to at the c. 200 CE
Severan Bridge in Türkiye (the longest known extant Roman stone arch). The Ponte Sant'Angelo, built during the reign of
Hadrian, has five arches each with a span of .
A bridge in Alcántara has piers wide, high, and arches with a span of . Another bridge over the Bibey River in Galicia has a pier wide, arches with a span, side arches, and an arch spanning . Wider spans increase the bridge's drainage, reduce water pressure on the
spandrels, and reduced the bridge's weight.
Trajan's Bridge over the
Danube featured open-spandrel segmental arches made of wood (standing on high concrete piers). This was to be the longest arch bridge for a thousand years both in terms of overall and individual span length. The longest extant Roman bridge is the
Puente Romano at Mérida.
Stone bridges
Roman engineers would begin by laying a foundation for building bridges across moving bodies of water. At first, they used heavy timbers as
pilings in the riverbed, but a later technique involved using
cofferdam to redirect the water and then laying a stone foundation in the area. Work was exclusively done during the
dry season to aid in constructing a foundation. This ensured as many piers as possible were accessible. There is some evidence that to construct bridges rivers were diverted. Trajan might have performed such a practice when constructing his Danube bridge. Roman engineers might have diverted rivers using rudimentary methods and tools. Sometimes dirt was added to the foundation. A bridge's foundation could be built above or below
water level. Building the bridge above water level resulted in a need for a wider span.
Bridge's tunnels and spandrels were designed to decrease the weight of the bridge and function as
.
The Pons Aemilius probably had stone piers with wooden roadbeds and arches.
In the 2nd century, arches became thinner, and spandrels became flat and pierced with holes. They were constructed using a wooden frame to hold wedge-shaped blocks in place. Afterwards, the wooden frame was removed, but the weight of the keystone, the last block to be put in place, held it together.
Roman piers were thick enough to support the pressure of an arch. Stone arches allowed bridges to have much longer spans.
Two niches carrying were inserted between . They were then put above the framed starlings. Roman bridges had , between which images of were often inserted.
Marcus Vipsanius Agrippa used ashlar and bricks to cover the outside of bridges and concrete for footings and water channels. Ashlar was used because large amounts of wood were needed to cast the concrete.
Brick bridges
Although
were used to build many bridges, they were far more commonly used to build aqueducts. Bridges built from bricks were rare as bricks often failed to survive
erosion.
The brick bridges that were built were generally used by the military, and they used construction techniques called
opus vittatum and
opus mixtum, the latter alternating rows of bricks in
opus reticulatum.
Examples are bridges in Carmona, Palomas,
Extremadura, and the Ponte della Chianche in Italy. One brick bridge in
Ticino,
Switzerland, has stone arches and brick spandrels.
Bricks were sometimes used to create parts of bridges, such as vaults, piers with
, and brick and mortar
rubble.
Wooden bridges
Early Roman bridges were wooden, including one constructed by Apollodorus and the Pons Sublicius, the oldest bridge in ancient Rome, and they were probably common across northern Europe and the
Tyrrhenian Sea;
however, because of their lack of durability few have survived to the modern day.
These bridges were supported by wooden
Trestle support spanned by horizontal timbers and reinforced with
, and they were possibly
. In order to simplify the process of cutting trees, multiple shorter timbers were used.
Wooden poles were driven into the ground, and flat pieces of timber laid across them to create a flat surface.
Other early techniques used to build wooden bridges involved , sometimes they were moored side by side. Workmen would raise weights, sometimes by rope, then it would fall down onto the piles. This method of construction, called pile driving, was necessary for wooden bridges to properly function. Because this technique created , which are enclosures build to pump water out of an area.[Chisholm, Hugh, ed. (1911). "" . Encyclopædia Britannica. Vol. 6 (11th ed.). Cambridge University Press. p. 649.] The base for the foundation of the bridge would be put in this area.
Pontoon bridges
were built by laying boats from side to side across a river.
During
Julius Caesar's
Gallic Wars in
Germania, he built bridges by driving wooden piles into the
stream bed from floating platforms and fixing beams at
across them to create trestles.
Trajan built another bridge supported by stone during the Dacian Wars.
Roman engineers gradually developed new techniques to build bridges, such as oval-shaped bases and pierced bases to facilitate the movement of water. Many bridges would have
marble or
, but these bridges were likely used exclusively by government officials because of the difficulty and expense of carving marble artwork.
Typology
There were three major types of Roman bridges. These were wooden, pontoon, and stone bridges. A list of Roman bridges compiled by the engineer Colin O'Connor features 330 stone bridges for traffic, 34 timber bridges and 54 aqueduct bridges, a substantial number still standing and even used to carry vehicles.
A more complete survey by the Italian scholar Vittorio Galliazzo found 931 Roman bridges, mostly of stone, in as many as 26 different countries (including former
Yugoslavia; see right table).
A segmental arch is an arch that is less than a semicircle.
The Romans built both single spans and lengthy multiple-arch
Roman aqueducts, such as the Pont du Gard and
Segovia Aqueduct. Their bridges often had flood openings in the piers, e.g. in the
Pons Fabricius in Rome (62 BC), one of the world's oldest major bridges still standing.
There were two main types of wooden bridge in Britain. Small timber bridges with , and large ones made of stone and wood. Throughout the rest of the Roman world, except for northern Europe, arched bridges made of stone were common. This was likely due to the climate and rivers of the regions. Rivers were much calmer and water levels were lower in the southern parts of the Empire. This ensured foundations were easy to construct. While in the northern parts it was much harder to lay down foundations due to the high water level, muddy water, and substantial waterflow.
Location
+The location of all 961 known Roman bridges[Galliazzo 1994, p. 2 (Indice). Galliazzo's survey excludes Late Roman or Byzantine structures.
]
!Europe
!830
!Asia
!74
!Africa
!57 |
| Italy | 460 | Turkey | 55 | Tunisia | 33 |
| Spain | 142 | Syria | 7 | Algeria | 18 |
| France | 72 | Jordan | 5 | Libya | 5 |
| Germany | 30 | Lebanon | 4 | | |
| United Kingdom | 29 | Israel | 2 | | |
| Portugal | 14 | Iran | 1 | | |
| Yugoslavia | 13 | | | | |
| Switzerland | 11 | | | | |
| Greece | 10 | | | | |
| Netherlands | 4 | | | | |
| Bulgaria | 3 | | | | |
| Luxemburg | 3 | | | | |
| Albania | 2 | | | | |
| Austria | 2 | | | | |
| Belgium | 2 | | | | |
| Romania | 2 | | | | |
| Hungary | 1 | | | | |
Opus pontis
The costs of building and repairing bridges, known as
opus pontis ("bridge work"), were the responsibility of multiple local municipalities. Their shared costs prove Roman bridges belonged to the region overall, and not to any one town (or two, if on a border). The Alcántara Bridge in
Lusitania, for example, was built at the expense of 12 local municipalities, whose names were added on an inscription.
Later, in the
Roman Empire, the local lords of the land had to pay tithes to the empire for
opus pontis.
The
Anglo-Saxons continued this practice with
bricg-geworc, a literal translation of
opus pontis.
Examples
Built in 142 BC, the
Pons Aemilius, later named Ponte Rotto (broken bridge), is the oldest Roman stone bridge in
Rome, with only one surviving arch and pier. However, evidence suggests only the
abutment is original to the 2nd century BC while the arch and pier perhaps date to a reconstruction during the reign of
Augustus (27 BC – 14 AD).
[Platner, Samuel Ball, A Topographical Dictionary of Ancient Rome, ed. Ashby, Thomas, London: Oxford University Press, 1929 Thayer,, University of Chicago, Accessed 9 June 2021]] The Pons Fabricius, built in 62 BC during the late Republic, is the oldest Roman bridge that is still intact and in use.
The largest Roman bridge was Trajan's Bridge over the lower
Danube, constructed by Apollodorus of Damascus, which remained for over a millennium the longest bridge to have been built both in terms of overall and span length.
Large river bridging
Roman engineers built stone arch or stone pillar bridges over all major rivers of the Empire save two: the
Euphrates, which lay at the frontier in the Roman–Persian Wars, and the
Nile, the longest river in the world, which was bridged as late as 1902 by the British Old Aswan Dam.
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Categories
The largest rivers to be spanned by solid bridges by the Romans were the
Danube and the
Rhine, the two largest European rivers west of the
Eurasian Steppe. The lower Danube was crossed by least two (Trajan's Bridge, Constantine's Bridge) and the middle and lower Rhine by four different bridges (the
Roman Bridge at Mainz, Caesar's Rhine bridges, the
Roman Bridge at Koblenz, the
Roman Bridge at Cologne). For rivers with strong currents and to allow swift army movements,
were also routinely employed.
Judging by the distinct lack of records of pre-modern solid bridges spanning larger rivers,
the Roman feat appears to be unsurpassed anywhere in the world until into the 19th century.
See also
-
List of Roman bridges
-
Bridges in Rome
-
Record-holding bridges in antiquity
-
Roman architecture
-
Roman architectural revolution
Footnotes
-
Fuentes, Manuel Durán: La construcción de puentes romanos en Hispania, Xunta de Galicia, Santiago de Compostela 2004,
External links
