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Railways and Emcor (formerly Drake & Scull), to close St Pancras as it had been known for almost 140 years and begin a massive restoration programme in and around the Barlow Shed. Phase two of the extension — the remaining nine platforms and their roof structure — could then start. “We have been on site for around two and a half years now. It’s a huge slender canopy we are building with few supports,” says WSS contracts director Alex Harper. “We designed and built temporary steelwork to support the splice side of the first phase of the roof. Now we are back on site for phase two, the cross- Urban Exposure/CTRL trusses have been continued and the temporary works removed during night-time closures of the operational railway part of the extension.” “Highly architectural” is how Harper describes the Highly architectural canopy takes shape entrance and side screen steelwork. Where possible, welded or hidden bolted connections have been used. A third of the roof Watson Steel Structures (WSS) is progressing the The main roof trusses are very slender being only was built in Phase I second and larger phase of the St Pancras extension 2.6m deep but up to 36m long. Prior to starting on to accept diverted steelwork, which amounts to around 3000t in total, site, lifting trials were carried out at Bolton to prove lift Midland Mainline from its Bolton yard. The first phase — the easterly beams specially designed by WSS. Delivery to site is trains while the Barlow half of the steel canopy structure — was completed after 7pm to keep disruption to a minimum. shed was restored to allow four new platforms to be opened for Midland “It’s a very challenging job,” says Harper. “Logistics Mainline services in April 2004. are complex and we have to coordinate closely with This enabled Contract 105 principal contractor CORBER’s concreting team, which we are currently CORBER, a joint venture of Costain, O’Rourke, Bachy chasing northwards down the job.” the gable end of the Barlow Shed. For the space All change at Barlow shed FACT FILE between, Glover’s team has designed a shallower St Pancras Station transition roof structure to “telegraph” views Restoration of WH Barlow’s St Pancras train shed entails cleaning Extension — part of between the old and new structures. and repairing the arch’s wrought ironwork above a massive arched Channel Tunnel Rail Link “The new roof meets the Barlow Shed where scaffold and platform. But conversion of the old station is also Section 2 Contract 105 platforms for Midland Mainline and Kent commuter necessary. Client: services will terminate and where passengers will The roof is being restored to its pre-World War II condition with Union Railways Engineer and Architect: come up from the new Thameslink station beneath. ridge and furrow glazing over the crown and Welsh slate over the Rail Link Engineering It will be a very busy and important concourse remainder, but the platform structure is being substantially altered. Main contractor: area,” says Glover. The Victorian platforms and track were supported by 800 Costain, O’Rourke, Bachy The transition roof will be a grillage of 1.1m deep wrought-iron columns and a grillage of wrought-iron beams. Euro- and Emcor joint venture plate girders supporting pyramids of glass and star trains will enter at the same level, but on a new heavily rein- (CORBER) designed to create an atrium effect. It will hang from forced concrete trackbed. Below, what was originally an undercroft Steelwork contractor: eight groups of four 30mm Macalloy bars which for beer storage and more recently a network of small businesses, Watson Steel Structures Steelwork tonnage: will drop from needle beams to be connected to the will become the arrivals hall with ticket and passport control. 5200 tonnes Barlow arch. Numerous escalator and light wells are being cut out of the Project value: £400M Erection of the main extension roof by Watson wrought-iron structure to connect the two levels and whereas the (overall) Steel Structures is progressing well (see box). grillage of beams will become redundant, most of the columns will Connection to the Barlow Shed, however, is a remain to support the new trackbed. section that remains to be tackled. Eurostar trains “The Barlow Shed was built with indicative will arrive in 2007 drawings, so little information exists in relation to the gable end of the arch,” says WSS contracts director Alex Harper. “The gable has to be surveyed before we can model the structure and fabricate the height scaffold for the structural survey. The final CJW Photographic Services/CTRLWhen alterations to the old structure are nearer end steelwork to connect with it.” completion, WSS will be given access to the full steelwork will then be erected to produce what should be an awesome mix of modern and Victorian engineering. NSC October 2005 19


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