King’s Cross in London, UK, is home to a huge 67-acre redevelopment scheme, situated to the north of the recently refurbished railway stations of Kings Cross and St Pancras. The rich industrial heritage of the site has been embraced by the developers, King’s Cross Central Limited Partnership, who have respected the physical remnants of the past, incorporating them into the new development.
Among the most distinctive and beautiful features to be retained is a triplet of gasholder guide frames, constructed in 1867 and now Grade II-listed. The triplet was dismantled in 2001 to allow the construction of the Channel Tunnel Rail Link, and this offered an ideal opportunity to comprehensively refurbish it and relocate it to better suit the wider masterplan for the site.
The triplet is currently in South Yorkshire under refurbishment by Shepley Engineers. At the start of 2016, the restored Gasholder structures will be transported from Yorkshire back to London to be reassembled. There are 123 frames, each one weighing between eight and 10 tonnes.
Gas Holder No. 8 has already been restored and re-erected to the west of the triplet site, overlooking the Regent’s canal. It is currently being turned into a public urban park, 40 metres in diameter, with landscaping designed by Dan Pearson, gold medalist at RHS Chelsea Flower Show 2015. Dan Pearson will also be devising the landscaping for the triplet Gasholders and the wider King’s Cross estate.
Wilkinson Eyre won a design competition in 2005 with a concept for three residential buildings to be housed within the elegant cast iron frames. The concept proposed three drums of accommodation, providing 145 apartments of studios, one, two, three and four-bedroom apartments.
These will be located at differing heights to suggest the movement of the original gasholders which would have risen up or down depending on the pressure of the gas within. A fourth, virtual drum shape, located at the centre of the frames, forms an open courtyard.
Each residential building will be independently supported and is set back from the guide structures. The cladding is composed of modular vertical panels of steel and glass textured with a veil of shutters which can be adjusted to give shade and privacy to the occupants.
Despite being over 150 years old, the Grade II gasholder triplet is in remarkably good condition, largely preserved from decay by its 32 layers of historic paint. Once this paint is removed the restoration process involves the laborious task of manually inspecting every one of the more than 650 components to identify stresses, and repair them where necessary.
The biggest challenge of the triplet’s new incarnation was whether it could be re-erected as a self-supporting, stand-alone structure, inside which the apartment buildings could be built without touching the historic guide frame at any point. The juxtaposition of heritage structure and new contemporary architecture, with a physical distinction between the two, gives the most pleasing aesthetic solution.
To ensure the safety of this feat of engineering, the gasholder structure was tested for tensile strength and extensively modelled for wind-loading responses – both as large-scale individual columns, and as the complete triplet.
An extensive combination of established mathematical principles and advanced computer modelling processes undertaken over the past two years has proven that the gasholder triplet will not need temporary or permanent external support from the new buildings inside, allowing it to stand proud on its own both during re-erection and after it is restored to the London skyline.
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