Harilaos Trikoupis Bridge: the pylons of Hercules
Suspended from four pylons above a tectonic fault, this colossal project cofinanced by the ERDF is a key element in the Greek transport network and has a significant economic impact on the regions it connects.
A bridge over the straits of Corinth, between Rion and Antirion, connecting the Peloponnese with mainland Greece. For Harilaos Trikoupis, when he became prime minister of Greece in 1880, this vision could only have been a dream, unrealizable with contemporary technology. Another century needed to pass.
Three km from one bank to the other, 65 m deep, over a seafloor consisting of a bed of moveable sediment at least 100 m deep, with no accessible rock floor, in a seismic zone regarded as the most active in Greece on account of a tectonic fault lying between the south and north coasts ... Unthinkable even 20 years ago, the project was made possible by the development of technology for modelling the behaviour of material. The formula was inspired by a project for a bridge over the English Channel, proposed in competition to the current tunnel. On 3 January 1996, the Greek state granted the Franco-Hellenic consortium Gefyra S.A. a 42-year concession for the conception, construction, use and maintenance of the Harilaos Trikoupis bridge. The EU will extend significant financial support – ERDF grant, loan from the European Investment Bank (BEI) – to this ambitious building project.
A high-tech colossus
The work is titanic: 250 000 m³ of concrete, a 172,000-tonne metal skeleton, four masts, of around 220 m in height from the seabed to the top of the pylons, the pylons themselves holding up 368 cables in a fan formation which support a 2,252 m platform in total suspension. The Trikoupis bridge is actually the longest cable-stayed bridge in the world.
But its chief characteristic is the safety criteria in accordance with which it was conceived, giving it the ability to withstand 250 km/h winds, collision with a 180,000 tonne tanker travelling at 16 knots, or a seismic tremor registering above 7 on the Richter scale. Wide, shallow foundations were judged the best solution for stabilizing the structure. In the event of a major tremor, metal props on the supports, beneath the platform, would give way, releasing the platform to hang swinging, freely suspended from the cables, while giant shock-absorbers deaden the oscillations.
The project also draws attention for the technical feats carried out in the course of its construction. To strengthen the sea floor, large steel tubes were sunk in the positions chosen for each support; at 200 per support this represents a world first. The ground was then covered with a thick layer of gravel. Each of the piers, weighing 75000 tonnes, was constructed in a dry dock then towed by sea to the site; construction of the support then continued at sea, using a crane, until it had reached a sufficient weight to be sunk in the set place. This operation had not been previously accomplished either.
According to the preliminary conclusions of a study carried out by the University of Patras, activities linked to the construction of the bridge have contributed nearly 1.5 billion euros to the national economy, 67% of this in western Greece. Opened to traffic on 12 August 2004 – four months earlier than planned – the structure was crossed from the first year of use by 4.5 million vehicles, with a 40’ time saving in comparison to the ferry crossing (not counting waiting times). Recent data indicates that in 2005 44% of crossings were for professional reasons.
Situated at the intersection of two important axes (the Patras-Athens-Thessaloniki motorway, linking the country’s three largest cities, and the Kalamata-Patras-Igoumenitsa corridor in the west), the new bridge is a key element in the Greek transport network and will have important repercussions for local and regional development around Patras, in the south, as well as in the more rural zone of Aitolia-Akarnania in the north. It will benefit tourism by offering more direct access between sites such as Delphi in central Greece and those in the Peloponnese.