The tallest building in the City of London will be topped out today.
Standing at 278m tall, 22 Bishops Gate Street, will become the tallest addition to the growing City of London skyline - standing 48m taller than the city’s previous tallest tower Heron Tower.
Designed by PLP Architects, WSP has worked as the project’s consultant, while Multiplex has acted as main contractor.
The 62-storey office tower will be the second tallest building in Western Europe, just behind the Shard which measures 310m.
However, 22 Bishopsgate will have London’s highest occupiable floor space, with a public viewing gallery and bar on the top floors accessed with dedicated lifts from the public lobby.
WSP took over the running of the project in 2015 at the site of the canned “Pinnacle” project, which was little more than a hole in the ground, with the basement and tower foundations renamed by Londoners as “The Stump” after former developers backed out after the project became non-profitable (see picture below).
Bishopsgate tower construction, november 2010
Source: By Jon Blathwayt - https://www.flickr.com/photos/jonblathwayt/5143424544/, CC BY 2.0, https://common
WSP project engineer Alex Black-Roberts told New Civil Engineer that to keep the project viable, WSP would had to maximise the floor space within, which presented the first challenge as the existing Pinnacle foundations were too small for the final version of 22 that designers had drawn up.
“One of the biggest engineering challenges was building a much bigger building on the smaller existing foundations [left over by the previous developers],” he said. “We snitched these together with our new foundations, reusing 100% of the Pinnacle foundations and 50% of the basement, all of which was strengthened with our own new piling.
“Without building the bigger footprint on the smaller foundations, the project would have been unviable,” he added.
On the 37th floor three pairs of outriggers on each side of the building connect the steel frame to the concrete core. This has the benefits of allowing engineers to build wider floors by reducing stress exerted on the building by high winds, but also allows for a smaller core – maximising usable square footage in the building.
Logistics involved in such a tall build presented another challenge, Black-Roberts said. “For a building this size, and with over 1,000 people on site, just getting people, plant, and materials in and out, and up and down, has been a real challenge we had had to over-come with a balanced schedule for the internal hoists and [four tower] cranes.”
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