Last month Russian prime minister Dmitry Medvedev declared the new world-record cable stayed Russky Island bridge a “beautiful, unique” structure as he opened it to traffic. Mark Hansford was in Vladivostok before him to speak to those who have made it happen.
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Big bridges have been used by governments as a show of economic might for centuries, from London’s Tower Bridge, to Sydney’s Harbour Bridge and San Francisco’s Golden Gate Bridge. That tradition is showing little sign of abating, with two of the world’s most dominant superpowers battling it out to have the world’s longest of the most modern type of big crossing - the cable stayed bridge. And it is the Russians who have edged ahead following the inauguration in Vladivostok last month of the 1,872m long Russky Island bridge.
With a central span of 1,104m it is only slightly longer than that of China’s Sutong Bridge which has a central span of 1,088m, but it is enough to take the record. And it is the record, and the statement of power that goes with it, that Russia wants to make in the old Soviet port of Vladivostok as it gears up to host a major economic summit next month.
“This is a magnificent looking cable stayed bridge that has been built by the teamwork of excellent professionals”
Dmitry Medvedev, Russian prime minister
Federal and state governments have been pumping RB204bn (£7.2bn) into the city’s roads and railways as it prepares to host the Asia Pacific Economic Cooperation (Apec) summit. The Russky Island bridge is the biggest single investment, although perhaps more impressive is the city’s Golden Horn bridge with its 737m central span (see box).
But it is the Russky Island Bridge of which the Russian government is most proud. It connects the continent with the small Siberian Island of Russky, where the Apec summit will take place in a vast convention centre and hotel complex built for the job and as a future home to the Far Eastern Federal University. Heads of government from across the Asia-Pacific region will therefore cross the bridge, getting a first-hand demonstration of Russian engineering prowess.
Speaking at the inauguration last month, prime minister Dmitry Medvedev warmly congratulated the Russian bridge builders and spoke of how “really very proud” he was of being with them and to be among the first people to travel over “this beautiful, unique structure”.
“This is the opening of a magnificent-looking cable stayed bridge that has been built by the teamwork of excellent professionals,” he said.
But it’s not all down to Russians. For, while Russian legislation demanded a Russian contractor - USK Most got the contract - and a Russian designer - Mostovik - the key component in any cable stayed bridge - the cable stays themselves - were designed and installed by French specialist Freyssinet.
Indeed, when NCE visited in June, ahead of the inauguration, Russian transport vice-minister Oleg Belozerov was keen to highlight the eagerness of the Russian government to bring in international expertise. “The president [Vladimir Putin] himself was keen for the excellent experience of international firms,” he said. “We are keen for consortiums to be made up with foreign experience, and projects for the Apec conference were a good place to show that.”
Vladivostok’s mayor Igor Puchkarev was more glowing still. “We are very excited about the appearance of new bridges in our town and it is due to Freyssinet that we have them,” he said. Freyssinet also supplied the cables and provided technical support for the Golden Horn bridge.
Freyssinet’s world-renowned expertise in long-span cable stayed bridges was unquestionably vital for Russky Island. While only a modest increase in length on Sutong bridge, it is being built in a much more testing environment. Siberian winters are, after all, world-renowned as being particularly harsh and the bridge will have to withstand a marine environment with temperatures as low as -40°C and design wind speeds of 36m/s. By comparison the design wind speed on the 856m span Pont de Normandie was just 15m/s. Freyssinet’s knowledge was therefore seen as key and it carried out design, production and installation of the cable stays and damping system. It also carried out an expert appraisal on behalf of the Russian Ministry of Construction to validate the superstructure design, and brought in world-renowned bridge designer Michel Virlogeux to advise Mostovik on its deck design.Virlogeux’s input was to ensure that the deck had a cross-section in the shape of an inverted aerofoil to give it negative lift and better stability under wind loading. He also advised on optimising the dimensions of the towers. But he is modest about his contribution. “This one is a very classical design,” he says. “But I like it.”
“We are keen for consortiums to be made up with foreign experience. Projects for the Apec conference were a good place to show that”
Oleg Belozerov, Russian transport vice-minister
The design is indeed a classical cable stayed bridge. It is completely symmetrical, with a central orthotropic steel box girder, 28m wide and 3.2m high. It has two 321m tall standard A-shaped reinforced concrete towers and features 168 parallel-strand cable stays with dampers placed on each one. The towers were built with self-climbing formwork and piles 2m in diameter were driven as deep as 77m below ground to support them.
Construction began in 2007 and the truly momentous moment - the moment Russky Island bridge became the world’s longest cable stayed bridge with a 1,104m span - happened in April when USK Most hoisted the final 12m long deck section 76m from a barge to its final position and welded it into place.
Yet even before that, records had been broken by Freyssinet’s cable team. Long span cable stayed bridges need long cable stays, and the ones on Russky are the longest and heaviest ever; up to 580m long and 65t in weight.
And herein lies the challenge. To keep wind loads down - wind effects on the cables themselves contribute about 55% of wind loadings on long span bridges - Freyssninet has used its patented compact cable stays which can contain around 20% more strands in their sheaths than conventional sheaths of the same diameter. This means the same vertical load can be carried by fewer cables, which in turn reduces the wind loadings.
Reduced wind loads
In fact, wind loads on the structure are reduced by a hefty 25% to 30% as a result. This translates into a massive knock on saving of 35% to 40% on the cost of materials for the pylons and deck.
The longest set of cables was installed earlier this year, but for Freyssinet the build-up started in July 2011 with the positioning of the first pair of 136m long, 4t cables at a height of 186m. From that date operations proceeded with the installation of eight planes of 21 cable stays culminating in March with the installation of the last - and longest - and heaviest - pair of stay cables at a height of 317m. These weighed in at a massive 65t each.
Each cable is made up of between 13 and 79 strands of 15.7mm diameter, with each strand comprising seven galvanised steel wires individually covered with a thin film of petroleum wax and encased in a high density polyethylene (HDPE) sheath.
The number of strands in each cable increases as the hanging angle increases - every degree from the vertical decreases the efficiency of the load transfer so the number of strands must be increased to compensate. The longest cables are by definition those that hang the furthest from the vertical and so need the most strands - 79 at Russky.
“Cooperation between us and the Russians was very simple because we share the same technical culture”
Jerome Stubler, Freyssinet
“The ultracompact stay cables of the bridge to the Russky Island are second to none in the world in terms of both the length and design,” says USK Most director Aleksey Baranov.
At its peak Freyssinet had 45 people working on site, with around 300 Russian workers trained by Freyssinet working under the guidance of USK Most to provide the support needed to install the cables.
From Freyssinet’s point of view it has worked a treat. “The co-operation between us and the Russians was very simple because we share the same technical culture,” says Freyssinet chief executive Jerome Stubler. “Working with Russians is easier than with many other countries,” he adds.
Since March Freyssinet’s effort has been focused on installing the dampers, used on all long span cable stayed bridges to provide aerodynamic stability. This has been taken to new levels of technical innovation on Russky.
Initially the dampers in use will be Freyssinet’s patented but now standard systems - installed where the cables meet the deck. On shorter cables Freyssinet’s Internal Radial Dampers are used. These are located inside the anchorage tubes and provide a smooth outer shape. On the longer cables these aren’t up to the job, and Freyssinet’s Pendular External Dampers are needed. They use piston dampers with a pendular lever system which can move around a rod hinged on fixed support.
They are bulkier looking, and could soon become a thing of the past as Freyssinet has agreed with client the City of Vladivostok to retrofit its newest damper system to the bridge once the hullabaloo of the Apec summit has passed. This will be the first use of its new damping cross tie. It has spent £600,000 developing the patented system and Stubler for one is eager to try it out.
“We got the patent one year ago but we agreed with the client six months ago that we will not install it for opening,” he says.
“But it complies with the specification and if we had installed it here we may not have installed normal dampers.”
Cross ties - often called aiguilles - are nothing new, Freyssinet installed them on the Normandie bridge in France. But aiguilles run across the cable array continuously and are unpopular with bridge architects.
Freyssinet’s system differs in that the cross ties run from just one cable to the next and so are less visually intrusive. It works differently too.
The general concept is the same - by effectively strapping pairs of cables together at their mid point, the structure becomes much more robust and resistant to wind loads.
Meanwhile Russian bigwigs from Vladivostok to Moscow are chomping at the bit to sample the Russky Island bridge experience for themselves.
“We are anticipating that president Putin is to come here in September when we host the summit,” says mayor Puchkarev.
“But I can reveal a secret - he wants to walk or drive over the bridge himself as soon as possible.”
Golden Horn Bridge
While Russky Island is thrust into the international spotlight by virtue of its record-breaking central span and its role in Vladivostok’s hosting of the Apec summit, its neighbour the Golden Horn bridge is the one that is being celebrated locally.
The locals are proud of their city, which they see as the San Francisco of the east - and it’s easy to see why - it’s hilly, it’s coastal, it spends eight months of the year shrouded in fog, and for Russia its rather laid-back. All that’s been missing, apart from the thriving vineyards, is the signature bridge. And to the locals, the Golden Horn - not Russky - is the bridge claiming that crown.
“The Golden Horn bridge is the one we have been waiting most for,” says Vladivostok mayor Igor Puchkarev. “In fact, we have been waiting over 100 years.”
This view is partly borne out by its beauty but also out of practicality as it unites one of the city’s most densely populated yet under-developed suburbs with the centre and, it is hoped, will act as a catalyst for regeneration of the area.
“Until now it would take up to three hours to reach the city centre because of the traffic. Now this has journey been eliminated - now it will take only 10 minutes to walk to, and driving it will take even less. It is a very meaningful bridge for us,” says Puchkarev.
And in any other city it would be winning huge plaudits. With a main span of 737m and a total length of 2,389m it will be the ninth-longest cable stayed structure in the world by span when it opens this autumn.
It is also another triumph of Franco-Russian collaboration, with Freyssinet supplying and installing the 192 cable stays, providing technical assistance to contractor TMK and training personnel.
It also makes the area a hotbed of cable stay construction. “There is just 5km between the bridges. It means it is probably the biggest concentration of cable stays in the world,” says Freyssinet construction manager Damien Delbos.
Construction started in 2008 with Freyssinet starting to install cables in June 2011. Again, Freyssinet’s compact sheath was used to reduce the impact of wind. Its work was done in April.