TRAJAN’s BRIDGE ON DANUBE

SARASIJ MAJUMDER

 

In order to supply his legions fighting in Dacia, Roman Emperor Trajan ordered the construction of a 1,135 meters (3,724 feet) bridge across the Danube River. Apollo Dorus of Damascus, one of the best Roman architects, and Mathematician designed a fantastic ARCH bridge with Stone Masonry Piers and a Wooden Superstructure.

The bridge was fifteen meters (forty-nine feet) wide. It was nineteen meters (sixty-two feet) above water.

The Trajan’s Bridge was high enough to allow the ships to pass beneath.

The bridge enabled the Romans to move supplies and troops quickly over the Danube River and thus greatly contributed to the Roman conquest of Dacia in 106.

The Romans needed just three years to build a one-kilometre-long bridge

 

It was all a demonstration of intelligence, persistence, applied engineering and steady, focused work over long periods of time.

It was the best and most extraordinary example of this type of construction of that period, and was carried out by the Romans on the Danube River on 2^nd  Century A.D.

Apollo Dorus admirably designed and built the bridge over the course of 3 years and with this monumental construction the Roman legions were able to establish a road across the river and keep their supply lines open and secure in order to subdue the Dacians, mortal enemies of the Roman Empire. limes from the north of the empire.

General features

The structure was 1,135 meters long, as the Danube is about 800 meters wide in area and 15 meters deep, reaching 19 meters above river level. At each end there was a fortification (Castrum), which one had to pass through to cross the bridge.

The bridge, designed by the engineer Apollo Dorus de Damascus, was made up of twenty wooden arches resting on square masonry pillars. Each arch measured 52 meters in span and the pillars were 20 meters on each side and up to 45 meters high and were made of Stones, bricks ., mortar and pozzolana cement.

The Romans needed only three years, from 103 to 105 AD, to complete the bridge. That was an astonishing feat since the bridge was 1,135 meters (3,724 feet) long.

Apollo Dorus didn’t diverted the river to dry out the river bed but made it possible to construct pillars made of  stone, bricks and mortar using ,what is known today a COFFER DAM TECHNIQUE..

The Romans used oak wood for the arches. The wooden superstructure was assembled on land and then installed on pillars.

Wooden arches, each spanning thirty-eight meters (125 feet), rested on twenty massive masonry pillars.

Pillars were forty-four meters (145 feet) tall, seventeen meters (fifty-eight feet) wide, and fifty meters (165 feet) apart.

Despite its exceptional dimensions, it was built in a very short time, between 103 and 105 A.D.. This speed has led some to speculate that perhaps the river was diverted during the period of construction of the bridge, however the Roman historian Dio Cassius denied it.

I recommend reading the novel by Santiago Poiseuille, volume II of the Trajan Trilogy.

The most interesting part is how they built the foundations or pillars of the bridge on a mighty river like the Danube and the solution is really great. Still it is used.

As you can see, two log barriers are built with huge trees separated by about 4 meters and filled with stones and trampled earth creating a central space of more than 50 X 30, this is dried by means of a tube pump system. designed by Archimedes of Syracuse. Once the space is reasonably dry, the dry work begins with appropriate materials and finally the pillar is lifted that serves as a support for the arches built in wood and on top of it the platform also in wood and which is the road itself to give passage to troops, wagons, sieged weapons and troop supplies. On both sides were built protective Forts that controlled the passage.

Works were done from barges and using huge cranes to move and place stones and materials; More than 3,000 men worked during a constant construction period of no less than 3 years. The bridge served without major problems for more than 50 years and the RUINS of this incredible work of architecture are still preserved today. The Romanian government a few years ago ordered the demolition of some part of  pillars that prevented navigation on the river.

Genius is the name, not only of Apollo Dorus, but of the incredible Roman people who carried out lasting works over time, such as this bridge made of stone and wood.

The cofferdam system is still used today to build modern bridges... and its principle has been conceived for millennia.

I explain it to you with a sketch below:

 

Unfortunately, Trajan's Bridge was demolished in the 3rd century, by order of the Roman emperor Aurelian, during the retreat due to the attack of barbarian tribes. The bridge was built in a very short period of time during that time, from 103 to 105. But there are still some fragmentary ruins of the bridge's piers that are still visible today. It is located near the city of Drobeta-Turnu Severin in Romania and Kladovo in Serbia.

 

References:--

1.      Roman History—Gibbon., and other sources, my visit.

2.