The £44 million project undertaken by Network Rail to redevelop and transform Manchester Victoria station includes a state-of-the-art roof which has been constructed around 15 curved steel ribs, all of which are unique in both size and curvature.
The task of producing the curved structure for this project was awarded to expert tube and metal profile bending company Barnshaws, which conveniently has one of its production facilities located in the city.
The new £16 million roof will provide a modern and bright feeling to the new concourse, which has been designed to be sympathetic with the original Grade II listed building and also to provide sufficient capacity for future expansion. For the main contractor tasked with delivering the project, precision and timing were key to the overall success of the refurbishment.
From the start, the design of the new roof was going to pose some tough challenges for the fabricators, Severfield (UK). Each rib has a unique design, not only in length but also in width, depth and curvature, so the actual manufacturing of the ribs required a high level of precision. In addition, the ribs had to be made in sections up to 20 meters in length and then transported to the site before final assembly and installation.
From the outset the engineers from Severfield (UK) consulted with Barnshaws to discuss the best way of creating and manufacturing the design so that it could be installed in the most efficient manner. As it turned out this would involve two of the largest cranes in the country and some millimetre-perfect construction as well as precise timing.
Greg North, Commercial Director for Barnshaws, comments: “We have worked with Severfields on a large number of projects in the past and we understand each other’s capabilities and strengths. For one particular part of the project we were able to provide 350mm square hollow section (SHS) steel that was curved to a 7000mm radius at certain points with no distortion to the section, thanks to our specialised methods of bending.”
In fact, all of the SHS steel required 3 or 4 different radii within each length but this is all within the capability of Barnshaws and the engineering team, who were able to deliver these components, on time, to Severfield’s. The second part of the project required steel plate measuring up to 550mm wide by 50mm thick to be curved to various radii in order to make the larger sections of each rib.
Each plate section has been curved to a specific set of dimensions to allow it to be assembled into a curved box-section by Severfield (UK). These are then transported to the station site where they are welded together to create the complete rib which is then carefully positioned and installed. Each of these unique ribs has required considerable precision and tight tolerances to ensure the installation process went smoothly.
Most of the curved beams were installed using the UK’s largest telescopic crane, a 1,200 tonne behemoth, while rib 9, the largest of the ribs measuring 96 meters in length and weighing nearly 86 tonnes, was installed using a 750 tonne crawler crane, which is one of Europe’s largest of its type.
This in itself created complications due to the live tracks that run beneath the new roof structure and the whole installation process required close cooperation with Network Rail. In this way, the short periods during which the tracks can be made safe could be utilised as efficiently as possible, ensuring the roof structure was installed on schedule.
With the main ribs installed, the smaller subsections could be fitted that would support almost 400 ETFE (Ethylene Tetraflouroethylene) panels, similar to those used in the Eden Project and Manchester Piccadilly station. As with the steel sections, each one of the polymer roof panels has a unique shape and relies on the precision of the steelwork to ensure a perfect fit.
Greg North concludes: “The design of this project has posed some challenges to all of those involved in making it a reality, but together we have succeeded in delivering a fantastic structure that will greet everyone visiting Manchester Victoria.”
