CIVILS, CONSTRUCTION & STATIONS
Rib 9 being lifted into place at Manchester Victoria on the morning of Sunday 3 August.
Prime minster David Cameron and chancellor George Osborne visited the site in July 2014.
Hoisting and positioning
The precise choreography of the hoist and positioning were achieved using Severfi eld’s own 3D laser technology, which allows for the pinpoint alignment of complex connections so that structures fi t to tight tolerances.
Boxes are made up of four pieces of plate section nested and cut to their unique profi le and assembled as an open lid box, welded fully inside then closed with top plate and welded on the outside. Once fully welded to the correct shape, Severfi eld sets all the connections to tight tolerances. To achieve this, it employed its own leading-edge shop assembly method, developed over the last decade, that employs 3D models and laser technology, shooting xyz coordinates to the bolt holes, which in turn provide a confi dent fi t-up on site.
Source: Severfi eld
Hulme explained: “The LR 1750 crane we used for Rib 9 has got a 56-metre main boom and a 56-metre buffi ng jib, which makes it more versatile for us to stretch out to a possible 92-metre radius, and we can actually move the crane because it’s tracked. So, when we pick something up, we can move it into position before it then leans out to put the rib into place.”
The strops were attached to the rib, the crane located in its correct position, and then the rib was lifted out of the toast rack while the team ensured everything was balanced correctly and in the right position.
“Then it’s a waiting game,” Hulme said. “We were in the hands of Network Rail and MRDL, the Metrolink operators. As soon as they gave us the green fl ag, we were allowed to slew around.”
The new roof doesn’t actually touch the existing building – the ribs are supported by ground- level buttresses and a column, from which they cantilever to the building. This avoids putting excess loads onto the existing historic structure.
Rib 9, because of its length, has two columns and two pinned connections. “Ribs 1-8 have only one pinned connection, so there was an extra operation involved in this one,” Hulme
said. “The rest had been cantilevering over the middle column. This one, because the cantilever was over 30m, had to have another column at the end. This will happen on Rib 10 and Rib 11 as well.”
The team dropped the rib down onto the second column, pinned it off , then dropped down onto the base to locate the Macalloy bars into the concrete buttress.
Hulme explained: “We then had to tie the girder off with two tying purlins at strategic points – our designer Mick Slack tells us where we have to put them – so we’ve got some stability within the structure as soon as we release the big crane.
“When we’ve got the crane ready, and once everything’s been tied off , and everything’s secure, we release the strops from the rib and then slew the crane back, and then hand back to Network Rail.”
Before the next rib could be installed, more stability purlins had to be installed within the structure, between Ribs 8 and 9.
Finishing the job
Following the successful Rib 9 lift – “an incredible achievement for us”, Hulme said
– the fi nal six ribs start descending in size again. Rib 10 and Rib 11 were both done in one weekend – August 9 and 10 – taking advantage of the fact that the Arena was closed for bi-annual maintenance. That lift involved a 500-tonne crane located outside the station, lifting items over the existing roof, while the big crane in the car park was used to lift Rib 10 into place.
The fi nal four ribs were done weekly, until the last one was fi nished on 7 September. Hulme expects the Severfi eld team to be on site for another two to three weeks doing fi nal infi ll purlins and gable steelwork frame, plus bolting-up checks and painting.
Severfi eld is supplying and erecting about 1,900 tonnes of structural steelwork for the project – not just the roof ribs, but also the mezzanine fl oor to link the station to the Arena, as well as lifts and a ‘feature staircase’.
The team has been using ‘4D’ construction sequence models to ensure the deliveries are precisely planned and tracked, as the logistics and site management aspects have been among the most challenging parts of the job.
Asked how challenging the Manchester Victoria roof structure has been compared to previous jobs he has worked on, Hulme told us: “It’s pretty much business as usual – in that we don’t do ‘usual’ structures. We do the structures no-one else wants to do. The last job I worked on was the Orbit structure at the side of the Olympic stadium. Up to this one, that’s been the most fascinating job I’ve ever worked on.”
Jed Hulme FOR MORE INFORMATION
RTM covered the Manchester Victoria upgrade in detail in our October/November 2013 edition. A video of the Rib 9 lift is online W:
www.youtube.com/user/networkrail
rail technology magazine Aug/Sep 14 | 29
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