Wednesday, 31 August 2016

Mersey Gateway August 2016 update

It has been 5 months since I last updated progress on the construction of the new bridge across the Mersey, the last blog about the project posted in May focused on the task of upgrading the road connections to the bridge.

Since the last update in March 2016 a great deal has happened and 2 of the 3 pylons that will eventually support the bridge are reaching their final heights. As of the 28th of August the north pylon was at a height of 102m, with only 8m left to take it up to its final height of 110m. The south pylon was up to 117m with another 8m to go as of the 26th of August and the central pylon was at a height of 59m as of the 24th of August.

South pylon

Central pylon

North pylon

A view of the 3 pylons together taken on 26th of August. 

Throughout August anchor boxes had been installed into the north and south pylons, the anchor boxes will be used to secure the stay cables which will hold the weight of the bridge deck. The south pylon which will be the largest contains 16 anchor boxes, each of which can hold 4 stay cables, 2 on each side. The central will house 8 anchor boxes and the north will house 14.

During July and August the form travellers which will construct the bridge deck were lifted into position on the north and south pylons, with the central yet to lifted. The form travellers work in a similar way to the movable scaffold systems (MSS) which are being used to construct the approach viaducts. 

The form travellers each act a mould into which steel reinforcement is placed and then concrete is poured to form a bridge section. Each bridge section will be secured with a stay cable anchored to the pylon. 

Once each bridge section is secured and the concrete has set the traveller then moves along, half of the travel supported on the bridge section just constructed and the other half jutting out to support the mould, ready to construct a new bridge section. This process is repeated until 2 form travellers working from each pylon meet in the middle. 

The south pylon with the form traveller in position. 

Over the past 5 months the MSS which has been constructing the approach viaduct on the Widnes side has been making steady progress, as of the 20th of August 8 spans had been completed. Work has now begun to extend the width of each span to the final 6 lane width.

To extend the width of each span a machine called a wing traveller (pictured below) has been installed. This machine rests on the constructed span and reaches out sideways to support 2 moulds (1 either side) onto which concrete is poured. Once the concrete is set the machine is moved forward to repeat the process.

In Runcorn a second MSS is being assembled to construct the approach viaduct which will take traffic over the Manchester Ship Canal and onto the new bridge. This MSS will work in exactly the same way as the one on the Widnes side. 

Another large and key element of the project is the construction of Astmoor viaduct which will carry traffic from the A533 Central Express onto the new approach viaduct. This is complex and large structure which includes the construction of a new junction and a large viaduct which is close to industrial units, crosses a busy road and a busway.

This viaduct is being built in what could be considered a more traditional way. Piers have been constructed out of reinforced concrete onto which pre-cast concrete bridge beams are placed. 

Bridge beams over the busway

Piers already constructed ready for beams to be placed over Astmoor Road

The project appears to be progressing well and is on track to open in 2017. I'll be sure to keep up to date with the latest progress right up until the opening day. 

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