Construction project of the bridge over the Nervión River at kilometric point 4 901 of the Bilbao-Donostia line
Client:
Budget:
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ETS-URA
4,600,000 €
Itziar Amaia Fernández Hernández / ETS
July 2010 - March 2012
Completed
Etxebarri (Vizcaya)

Description

The first step is the construction of the bridge at its initial position, taking into account that we have the current bridge with its stacks very close by.
The requirements of the stretch of the provisional track and the existing wall mean that the current pedestrian bridge has to be demolished to construct the new bridge.
Under these conditions, the bridge construction has been tackled by complete formwork supported by some provisional stacks on the riverbed, without initially constructing the arch.

Under these conditions there are 16 metre spans, situated between the supports four provisional stacks. Each stack is made up of two independent piers, one below each girder. The stacks closest to the supports are on the river banks, with easy direct foundations because the rock is almost level with the water.

The other two stacks are in line with those of the current bridge. The closest to the left bank is supported on the prolongation made downriver from the foundations. Both piers are on this base, which can resist the load of the bridge. In the stack closest to the right bank, one of the piers is on the base of the current stack, which allows the pier to be built on it without altering the river. Only the second pier of this stack is in the middle of the river, but it is easy to access it and to make the foundations protected by the stack of the current bridge.

After the board is concreted it is kept supported on the provisional stacks to construct the arch over the middle point of the formwork.
After the arch is finished and the suspension cables tautened, the provisional supports are removed and the provisional track is assembled to divert the railway over the new bridge so that the current bridge becomes free from traffic.
This situation allows for the current bridge to be demolished using metal shears and hydraulic hammers.
After the current bridge is demolished the supports of the new bridge are constructed. These will have to be in prolongation, at least its upper surface, of the bridge’s supports in its initial position.
The following operation consists in ripping the bridge from the initial to the final position. This operation can be done pushing with jacks from the provisional supports, and supporting the bridge on skidshoes.
After the ripping has finished the provisional tracks are substituted for the definitive tracks and the definitive traffic starts over the new bridge,

With the bridge in its definitive position the provisional supports and stacks are demolished, and the definitive ones are finished off, thereby completing the construction of the bridge.
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