The first sections of this enormous steel structure are now being manufactured in the workshop, which will be put together on the left bank of the River Ebro. Currently, the platforms necessary for the assembly are being constructed on the river bed.
To construct the first inhabited bridge in the world over the River Ebro is an enormously complex task which is having its loose ends tied up in its design process by Dragados and Urssa. The challenge is to put this enormous structure together in thirteen months. The structure follows a curved line, is shaped like a Gladiolus and is to be located in front of the Third Millennium Bridge.
Its complexity has forced the constructor to introduce structural variants to ease manufacture and assembly, respecting the shapes and finishes given by its author, the 2004 Pritzker Architectural Prize winner, Zaha Hadid.
The Pavilion Bridge structure, which will be lifted obliquely over the river, is integrated by four base elements or diamond-shaped sheaths linked between one another, all having variable widths and depths of up to 30m. Only one section shall be constructed on the right bank, whilst the most complicated, which give the shape to the gladiolus to the bridge, shall be constructed on the left bank. In this part – as can be appreciated in the image – lateral trenches are being filled with soil which will act as platforms so that assembly-cranes may be placed for the works.
The Construction Director at the World Fair, Eduardo Ruiz de Temiño, explained that to do the Bridge Pavilion is like assembling a large steel tube over the river “two thirds over the right bank and one over the left”
The person responsible for Infrastructures, Miguel Ángel Soria, said that once the pieces are constructed in the metal workshop, they “be connected together on the left bank and when the tube begins to overshoot the river, it shall be linked up to cables on the hydraulic lift-crane, which shall be located on the central isle in the middle of the river.
The structure as a whole, offering a favorable profile to the flow of the river, shall be supported on both banks of the river and upon a central isle in the river. The President of the World Fair, Roque Gistau, assured “it will work as if it were a boat set upon three columns”.
So as not to delay the forecasted process in the initial Project, another artificial peninsula on the right-hand bank has been avoided, the side of greatest depth and the main part of the works has been preferred to be done on the left-hand side.
The first task to be carried out is the creation a series of spits of land on the left bank for foreseeable changes which could affect the structure under construction. These spits also allow the placement of beams to shore the mobile scaffolding units whilst the 100m span is being assembled on this side of the river.
The other part of the span, 150m in length, which will arrive from the left bank, will not be supported on a peninsula, and will be installed directly over the water, employing the same launching system Dragados used with the Lanjarón Bridge, (Granada). This system consists in launching the steel structure, and cantilevering it out as far over the river as possible and maintaining the deck raised by cables from an auxiliary crane installed on the central island.
Before launching, all the pieces in the 150m span will have to be assembled on the right bank on shores placed on longitudinal concrete beams. Afterwards, the falsework is dismantled and the structure shall remain supported on two transfer carriages or rollers and the launching will continue.
The next phase will consist in fixing the cantilevered structure with the structure on the opposite side, employing the cables from the crane situated on the central island.
The façades of the bride shall be assembled from outside employing mobile cranes, which shall travel from the peninsula on the left bank to the central island in the river. Doing this from the outside has the advantage, that as the timeframe to construct this emblematic building at the world fair is very tight, you are also able to work the inside of the Bridge Pavilion, on the 7,000m2 exhibition space which need a huge amount of assembly time. The Pavilion will house the exhibition “Water, a unique resource”, designed by the specialist in hydraulic resources at UNESCO, Carlos Fernández Jáuregui.
Also, a floating pontoon with a ‘Unite’ pump (material used to protect and waterproof concrete), served by tower cranes will allow all the structure to be coated.
Another two tower cranes with 70m jib, situated on the central island and the other on the right bank will help to drag half the structure until it connects with the other half. The two parts of this steel skeleton, braced with transversal ribs forming diamond shapes, set apart at distances of 3.6m, will meet at a central pier which is anchored 72.5m below the river. This is a record in piling in Spain in a Project of these characteristics. The aim is none other than to consolidate the foundations of the Bridge Pavilion to withstand the 7,000 tonne weight.
M. LLORENTE.
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