Queensferry Crossing getting a Sheerleg-up from Taklift 6
9 October 2014
Another busy week. Firstly, here's some media coverage of Deputy First Minister Nicola Sturgeon's visit to the project site this week.
In previous posts, we’ve talked about the Queensferry Crossing becoming ever more visible - the southern approach viaduct and all three towers have all appeared and grown significantly in the past 12 months or so.
But “becoming more visible” doesn’t really do justice to the spectacular goings on out in the Firth of Forth at the moment. Since early September Taklift 6, a frankly enormous sheerleg marine crane, has been operating back and forward from the Rosyth dockyard out to the towers.
Back in the summer we told you about the significance of the towers reaching deck level, we added that part of our focus would soon shift slightly from the vertical (tower height) to horizontal (building out the deck). That’s exactly what the 125m-tall Taklift has been assisting with. First, the temporary steel trestles (120t in weight, 50m high) and platforms that arrived in the first shipment from Shanghai in May have been fixed to the Central and North Towers (the South will follow soon). These 300t platforms support the erection of the first deck sections, as well as providing sufficient working space for the deck team.
The Taklift is capable of lifting up to 1,200t, which for a vessel floating on water and standing at 125m tall, is no mean feat. The video above hints at the exclusion zone placed around the Taklift when it is operating – when the crane departs the Centre Tower the busy shipping lanes of the Forth estuary resume immediately. This zone is for shipping safety but also because of four 600m long moorings anchoring the Taklift in position to the estuary bed. The most easterly of these anchorages is actually stretching way down under the Forth Road Bridge and some distance towards the rail bridge.
Taklift 6 has also been lifting “deck erection travellers” into position either side of the towers. These huge, 120t blue lifting frames will eventually assist with lifting every subsequent deck section until the bridge decks fanning out from the towers join up or meet the southern and northern approach viaducts.
Once the tower deck segments are in position, they are welded and bolted together. At the Centre Tower the continuation of the Powerjoint is cast in reinforced, post-tensioned concrete. This is the only fixed point of the bridge deck. As we already know from previous posts, the deck expands and contracts in either direction from the Centre Tower, gliding past the North and South towers with just lateral stabilisation joints with the changes in length being taken by the expansion joints at the north and south abutments. Concrete is then poured in the tower deck sections in situ. The towers are obviously still rising to their eventual 210m height during this period. At some point next year, the attaching of the stay cables between tower and deck can begin.
Finally, a small apology to classical music buffs. We used Tchaikovsky to provide some musical colour for our timelapse video of Taklift 6 but as many will know “The Waltz of the Flowers” is from The Nutcracker Suite, not the more obviously fitting Swan Lake. We have two excuses: firstly, the Waltz of the Flowers fitted the action very nicely and, secondly, we were restricted to the music we could use copyright-free. You don’t save £195m off the project budget by getting too choosey about your classical music you know!