STATION MODERNISATION & EQUIPMENT
“Originally, the through lines went down the west side of the bridge. When we were finished, they had to go down the east side of the bridge. In the north, there were a number of two-span independent steel beams that supported the railway line. The track was parallel to those bridge beams. In the finished lay-out, the track has to go diagonally across those bridge beams, which meant the bridge beams structurally just could not do it.
“So we had to put in a new trapezoidal bridge deck to accommodate the new track alignment. When we put the deck into place, we hadn’t finished the bridge deck at that stage, so we couldn’t put the track in this alignment. So we slid the bridge deck in, put the track back, in that position, but on the new deck, so that we already had the bridge deck in place, so that when we wanted to switch the track it was there and waiting for us.”
Widening the bridge
In early 2010, the first new rib arches were installed, as part of the widening of the bridge – it was extended 3 metres on its east side, and 6 metres on the west. The team made a virtue of the river access: each 45-tonne rib was delivered by barge, after close consultation with the Port of London Authority, who were “extremely positive and helpful”, Evans said.
Lifting in the arch ribs was a complex engineering challenge, which Evans was closely involved in due to his own experience with marine projects.
It involved a tandem lift from a floating barge – it was “very technical”, as Evans put it.
He added: “Widening the west side of the bridge was quite a challenge, because we had to put a piece of concrete onto the old foundation.
In July 2010, the first section of the new roof spine was installed. It is supported 5.8 metres above the deck level, on columns – it couldn’t be any higher for planning reasons regarding unobstructed views of St Paul’s.
Then in Christmas 2010 came the next key milestone: the track switch. Moving the tracks from the west side of the bridge to the east during the six-day blockade allowed the west side bridge deck to be replaced.
Another major logistical exercise was removing the massive truss that used to support the outside edge of what was platform 5. Concurrent road, rail and river span possessions/closures were required to lift the truss out.
In April 2011, the new escalators were
delivered to the station as single units, and the roof trusses were installed, while the removal
“The cranes would not have anywhere near the capacity to lift the pieces of pre-cast concrete, and casting it in situ would be unrealistic because of the tidal constraints. So, we cast a lump of pre-cast concrete weighing some 38 tonnes, five metres above where it finally needed to be. We made a platform five metres up in the air, suspended it on a steel frame and cables, took the platform away and lowered it down into its final position. That avoided the need for tubular piles in the river.”
The bridge widening on the western side made virtue of the old piers next to the existing bridge, which used to support the St Pauls railway bridge until it was demolished in the 1980s – fortunately a decision was taken at the time, on cost grounds, to leave the piers in place. On the eastern side, new concrete shoes were added to the bases of the existing piers.
Even more milestones
of the TPS was planned for the same months. A full Underground and road possession had been planned far in advance: but then with two months to go, the project team was told it had lost the road closure, due to the Royal Wedding happening the same weekend. It required quite the lobbying effort to ensure the removal could still go ahead, Evans said.
The south station opened in December and the Underground station reopened in February 2012, able to accommodate more than 40,000 passengers a day.
The major engineering works and near- constant weekend/evening blockades finished in May, when the new bay platforms opened. FCC’s improved services began running from May 19.
Some bridge works have been carrying on and will do after the Olympics, but none of these will impact passengers: these include painting the underside of the bridge, for example.
The solar panel array on the station roof across the Thames, as explained in the last edition of RTM, will be switched on this summer, providing half of the station’s energy needs.
The works over the last three and a half years have happened on time, though have dug into the Thameslink contingency budget. Network Rail spokesman David Wilson said: “The Thameslink programme is running totally on budget; Blackfriars is using some contingency from Thameslink – it’s an immensely complicated project and we’ve come up against difficulties.”
FOR MORE INFORMATION
Facts, figures and a detailed timeline are available at
www.networkrail.co.uk/ blackfriars
rail technology magazine Jun/Jul 12 | 69
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