The Rio-Antirrio Bridge is a modern engineering marvel that, at its heart, relies on engineering expertise and lessons from the past. Opened in August 2004, the bridge wowed engineers because it reflects and marks the progress of bridge building through history. The bridge is one of the longest multi-span, cable-stayed, suspension bridges in the world.
Credit: By Eusebius, CC BY-SA 3.0, https://en.wikipedia.org/w/index.php?curid=39009078
The bridge links the Peloponnese peninsula to mainland Greece. These landmasses have moved further and further away from each other over hundreds of years, subsequently creating what is known as the Gulf of Corinth. The 2 mile gap was not the only unique challenge the Gulf of Corinth presented to engineers. The other challenges were the strong winds in the middle of the channel, and the fact that the bridge was going to cross one of the largest seismic zones in Europe.
Too much ground to cover
A 2 mile stretch is too wide for a single span bridge; engineers realised they had to develop a multi-span bridge. In the planning stages the depth of the water posed the initial setbacks; the Gulf of Corinth is sixty meters deep.
The answer was to use hollow, concrete, floating barges. This engineering concept was the brainchild of engineer Guy Maunsell, who invented floating forts for the purposes of battle during World War 2. Offshore wind turbine operations use these floating barges and they are commonly employed in modern day bridge building. Between 1998 and 2001, the four hollow pier foundations, needed to construct the Rio-Antirion Bridge, were floated into place.
Avoiding Natural disasters
Instead of burying the foundations in the ground, they were set atop the seabed, which had been reinforced by steel bars and ten feet of gravel. This was to ensure that the bridge could move with the ground during earthquake activity, to reduce the risk of the bridge being damaged by an earthquake. This is now known as seafloor stabilization, but it was a first in engineering bridge building history.
To further avoid the seismic activity’s effect on the bridge’s structure, the engineers implemented jacks and dampers that absorb any earthquake activity. Basically, the bridge has enormous shock absorbers.
Credit: "GEFYRA - Nikos Daniilidis"
Furthermore, the bridge is completely suspended to ensure that earthquakes do not make the bridge sway. It is held in place by 348 cables. The cables are made of single strands of steel grouped together to form one large cable. The steel strands are more flexible and collectively stronger than iron. Previously iron had been used on bridges that had experienced catastrophic failure.
The Tacoma Narrows Bridge. Credit: Seattle Times
To guard against damage from the wind the bridge uses the same aerodynamic wind diffusing fairings and spoilers that you would expect to see on a car, but on a grander scale. The cables are also wrapped with spiral Scruton strakes that allow wind to flow around the cables instead of straight into them.
These civil engineering nuances of bridge building may have saved the Tacoma Narrows Bridge in 1940. It was given the nickname ‘Galloping Gertie’ due to the effects of the winds; its vertical sway caused catastrophic failure. The Tacoma Narrows Bridge disaster serves as a case study and explains why the Rio-Antirrio Bridge used a system of cable-stays and suspension bridge construction technologies instead.
The Rio-Antirrio Bridge is considered a modern masterpiece. The engineers are applauded for their considerations of past bridge failures, and for their ability to come up with solutions to problems that had never before been addressed in the industry. And that is why this bridge is considered a modern engineering marvel.
RION-ANTIRION BRIDGE - An Engineering Marvel - Dr. Carolyn Pararas-Carayannis. Web. 20 June 2017.
Panajotisx. "Rio Antirrio Bridge - Challenging Earthquakes." YouTube. YouTube, 19 Jan. 2014. Web. 20 June 2017.