Severfield is erecting five storeys of steel next to the Shard that will be topped with 22 storeys of concrete. CN went behind the scenes to see this highly unusual arrangement.
Project: Shard Place
Client: Real Estate Management (UK) Limited and Sellar
Construction manager: Mace
Steelwork subcontractor: Severfield
Structural engineer: WSP
The past decade has seen the land surrounding London Bridge station totally transformed.
As well as the ongoing redevelopment of the station, the change is most instantly recognisable in the presence of London’s tallest building, the Shard, which opened in 2013.
Next door is the Place, now known as the News Building, the ‘sequel’ to the Shard in the trilogy of Renzo Piano-designed buildings at London Bridge.
Now, the final instalment, Shard Place, is under construction on a site adjacent to both of the existing buildings. Once again being built by Mace as construction manager, and developed by Real Estate Management (UK) and Sellar, Shard Place will comprise 257,044 sq ft of space over 27 storeys.
Unlike its two predecessors, however, Shard Place will be a residential building comprising 148 apartments with a roof garden on the 16th floor.
The apartments will be housed in a traditional concrete structure – but what makes this building unusual is the highly complex steelwork that will support it. With numerous trusses and cantilevered sections that will transfer the concrete load to the ground below, the result will be a traditional concrete core sitting atop five storeys of structural steel.
‘A beast of a job’
Severfield is the contractor tasked with erecting this tricky structure on a design-and-build contract, and is in week six of an 18-week steel erection programme at the time of Construction News’ visit.
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The firm will build five storeys of steel, with the transfer structure leaving open spaces at the bottom to allow vehicles to enter the building’s basement, as well as allowing continued access to nearby London Underground vents and other utilities.
“It’s a beast of a job,” says Severfield project manager Kyle Fletcher. “It’s effectively a very complex steel transfer structure that supports residential apartments on top.”
Severfield design manager Ian Dawson, who worked with Andrew Pratt of structural engineer WSP on the structure’s design, echoes this.
“It’s a beast of a job. It’s effectively a very complex steel transfer structure that supports 27 stories of resi on top”
Kyle Fletcher, Severfield
“It’s certainly one of the most technically challenging projects I’ve been involved with,” he says. “It’s not particularly massive with regards to tonnage and the size of it, but what’s there is very complicated.”
Severfield will erect more than 500 pieces of steel weighing 1,580 tonnes in total. These will go up in a particular order due to the complex nature of the structure, the weight of some of the elements, and the tight footprint of the site.
Severfield mace shard place 5 crop test
“Conventionally you’d see a nice central concrete core with steelwork surrounding it – here it’s the opposite,” Mr Dawson says. “You’ve got a huge trussed transfer structure with a steel core built on top of that, which makes it highly unusual.”
The finished building required openings at the bottom for logistics access, leading to the design solution, which Mr Dawson says is “a bit like an umbrella structure”.
“You have the central core, but then you have these huge, cantilevered trusses that spring out from that core to form the base that the concrete structure sits on,” he says.
Tricky temporary works
At the time of CN’s visit the steelwork has reached level three, following on from a particularly complex area of work at level two, which featured some heavy trusses. The steelwork is being erected by two tower cranes, and the maximum capacity of one is 28 tonnes.
“A couple of the trusses on level two span around 20 m and are rather heavy, so some of them we couldn’t erect in one go,” Mr Dawson says. “So we’ve had to split them.
“For one in particular we had to almost remove the top boom to make it light enough to lift, erect the truss in position, put temporary works in to hold it, then finally drop the top boom of the truss in position. That was quite a challenge. [You have to make sure] when you erect it that it stays in its geometry, so you can get that top boom in.”
“For one truss we had to almost remove the top boom to make it light enough to lift, erect the truss in position, put temporary works in to hold it, then finally drop the top boom of the truss in position”
Ian Dawson, Severfield
There has been a significant amount of temporary works on the scheme to hold the structure in place as it is being erected. “We’ve got some heavy members that require quite a lot of temporary bracing,” Mr Fletcher adds.
Severfield has also had to change its approach to moving materials, designing ‘tilt frames’ to allow the trusses to be laid on their side rather than standing up on the back of the trailer – fitting them within the allowable limits for transportation.
“There are also some large raking box-section columns, with massive horizontal forces getting transferred through that, so you end up with quite an awkward piece to lift,” Mr Dawson says. “You have to set it up with temporary works and engineer the lift, so you actually lift the column on the rake, as it were, and can land it in the correct position.”
Steel, meet concrete
Another interesting element to the design comes at the top of the steel structure, at level five, where it will eventually interact with the concrete structure above.
“Built into the top chord of the truss, we’ve had to put in some very thick plates where concrete columns land and interface with the trusses,” Mr Dawson says.
Severfield Mace Shard Place 2
“These are bristling with shear studs to accommodate the concrete, and then directly underneath [this we will construct] plates that are built into the trusses. These will be stiffened to make sure we can get the load from the concrete column to the place it needs to go within the truss. When you’re landing a concrete structure like that on top of structural steelwork, you’ve got some massive forces to contend with, and transfer.”
Mr Fletcher emphasises the degree of collaboration that Severfield fostered with WSP. “We had a very good relationship,” he says. “We were really able to co-ordinate and work closely with them.”
“When you’re landing a concrete structure like that on top of structural steelwork, you’ve got some massive forces to contend with, and transfer”
Ian Dawson, Severfield
Mr Dawson concurs, having worked hand in glove with the engineering consultant himself. “You could have easily ended up crossing swords on a project like this if you’d not had the collaboration,” he says. “We were listening to each other, developing ideas, sometimes disagreeing on details but then changing the way we think – that’s why it went so well.”
The architect, Renzo Piano Building Workshop, has also been involved, with many of the structural steel details to be left exposed once the building is completed. “A lot of the complex details on the Shard were ultimately covered up, but here you’ll be able to see a lot of them,” Mr Dawson says.
Real Estate Management (UK) development director Paul Welterveden says: “It’s the third and final building of the trilogy, sharing distinctly similar architectural elegance as the Shard and News Building.
“The design was developed sympathetically to respect the primacy of the Shard while balancing the composition for the surrounding area.”
The project is progressing well, with Severfield slightly ahead of schedule as of CN’s visit. The firm is on track to finish steel erection before Christmas, returning early next year to complete the deck on level five before handing over.
The company will return to add beams to support the floor on level 16 at some point next year when required.
“For such a relatively small tonnage, the effort and complexity is quite surprising,” Mr Dawson says.
“I don’t think I’ve seen many structures like this at all, to be honest. It’s unique.”