Analysis

WSP’s digital approach to reusing steel sections and saving carbon

How the Elephant and Castle redevelopment will look - with exposed steel that has already served the built environment
How the Elephant and Castle redevelopment will look, with exposed steel that has already served the built environment and been identified for reuse by WSP’s new tool

New software integrated into Revit is enabling WSP engineers to reuse steel sections and save tonnes of embodied carbon at the redevelopment of south London’s Elephant and Castle shopping centre.

Consultant engineer WSP has developed a digital section-matching software that helps engineers with the reuse of steel members. The tool helps match pre-used steel sections with structural designs for new buildings, opening the way for a more practical low-carbon solution. 

It was initially developed by the consultant to use on the redevelopment of the Elephant and Castle shopping centre, in south London, which is using reclaimed steel beams and columns from other deconstructed buildings. Successful implementation there means the firm is now using the software on other projects too.

Given that a building’s structure – its frame and foundations – account for more than half its embodied carbon, engineers are urgently focusing on innovative ways of optimising structural design to cut emissions. Many planning authorities are looking for wholelife energy to be considered when they assess planning applications, and more developers are keen to embrace methods that can reduce it.

Traditionally, steel beams and columns from demolished buildings are sold as scrap around the world and then melted down and reused for various uses, including cars, appliances and also new steel beams/columns. All that uses up a hefty amount of energy.

David Leversha of WSP

“Scrap steel was selling for about £250/t. But new steel was in the range of £800/t to £900/t. That gave us the confidence that there was a commercial driver to make it work.”

David Leversha, WSP

Huge savings

Reusing the steel as structural components can provide huge carbon emission savings, explains David Leversha, director and decarbonisation lead for property and buildings at WSP, who has been leading on the work to reuse beams.

Leversha had the idea for recycling steel components about three years ago. “I read an article in the Structural Engineer magazine that featured a dozen examples from the last 20 years or so. I could see it was achievable on a bigger scale, but it was just not happening.”

In discussion with EMR, a metal recycling company, he established there were drivers that could make recycling work – for example, the volume of material, a price differential, and the huge savings in embodied carbon to be realised.

Leversha says: “EMR had 100,000t of structural steelwork going through their UK facilities per month. That’s over 1,000,000t per year melted down and remade into cars, washing machines, pens, and structural steel items. In terms of price, scrap steel was selling for about £250 per tonne. But new steel was in the range of £800 to £900 per tonne. That gave us the confidence that there was a commercial driver there to make it work. In conjunction with EMR, it was also established that reusing steel (rather than recycling) could deliver a 97% reduction in embodied carbon.”

Leversha and EMR set out to overcome potential barriers by establishing how the steel could be tested, sourced and procured. They also discussed with WSP colleagues projects in which recycled steel could be used and which clients might embrace the embodied carbon savings it would bring.

Sally Walsh of WSP

“We made the tool parametric so that we could change some of the depths, widths and weights of the steel elements and this would enable us to have even more matches and more reuse in the project.”

Sally Walsh

Software development

Sally Walsh, senior structural engineer at WSP, who led the development of the tool, was approached by project director Audrey McIver. She was working on the redevelopment of Elephant and Castle shopping centre on a commercial building, where developer Get Living was keen to take on board the idea.

She soon found that mapping steel beams for the new project against an inventory of beams held by the stockholder (which, as well as EMR, also included Cleveland Steel & Tubes) was labour intensive. “On this project, we had already completed our detailed design stage, so there was little scope for change. The matching process is an iterative one. You find one section and you find a match. You go back down the list, you find another section, and then that is a better match. So I was constantly going through this process and I thought I need software, an algorithm, something that can do this process for me.

“That’s where the development of the tool started. It was to speed up that process and make it more feasible and allow re-using of steel beams across other WSP projects,” adds Walsh.

Ingeniously, the software program picks each column, looks at the length, looks at the size and places that into the analysis model, in several ways and in different combinations using AI to indicate which is the best combination for the building. Walsh adds: “We made the tool parametric so that we could change some of the depths, widths and weights of the steel elements and this would enable us to have even more matches and more reuse in the project.”

The new software – simply known as the WSP Steel Re-use Tool – was written in Python coding language by Thomas McLean, one of Walsh’s engineering colleagues who specialises in digital design.

Integrating into Revit

Walsh says that since WSP created its software, others have also come along. The big difference, she says, is that theirs is integrated into Revit.

She explains: “That’s the big selling point from our side and what helps us really drive it into designs. Our output from the tool is an updated schedule that can be inputted into our structural Revit model and it flashes up visually which steel members are now designated for reuse.

The changing face of the Elephant

The redevelopment of Elephant and Castle town centre is a highly complex scheme, taking place in three phases. The land is owned by Get Living, with Delancey as the appointed development manager.

The new buildings replace the iconic original 1965 shopping centre with three residential towers, an office, a retail podium, a cinema, and a new building for London College of Communication, part of University of the Arts London.

Challengingly, the work is taking place above a key transport interchange for south London, with its mainline rail station, the Bakerloo and Northern underground lines and many bus routes. All of this infrastructure runs directly adjacent, above and below the site and had to remain operational throughout construction, which is due for completion in October 2026.

When it began in 2020, designing the building for reuse was not so high on the agenda. But the developers subsequently become keen to pursue a green agenda, including using repurposed steel beams to reduce embodied carbon.

“We’re running those initial match studies on new projects all the time to see the opportunities that we’ve got. What has been critical in enabling this supply chain to evolve is that we can provide construction drawings with all our reuse members identified. Using automated tagging information ensures that where it came from, the testing results, and any remediation works that are required, are linked directly to the steel member.”

Reuse in use at Elephant and Castle

The design has been completed for the structure of the office building that forms part of the Elephant and Castle town centre redevelopment for Get Living (see box), and work installing the steel is due to start on site in July.

The project originally had a total of 372t of designed steel, and substituting 20% of this with reclaimed steel – the percentage there were matches for – means the team will be able to achieve a projected saving of about 125t of carbon dioxide emissions. 

“The steel structure is exposed so we worked closely with the architect and the MEP engineer to make sure that those reclaimed sections would still work with the design aesthetic,” Walsh says.

Next steps

WSP is now using its new software tool on a commercial scheme in central London, Sloane Square House, where client CCG is adding an extension to its HQ. Walsh says they have been able to achieve a 100% match of steel components at the planning stage of design. However, one of the issues is that the concept of steel reuse is beginning to take off and demand is currently outstripping supply.

Leversha praised the work that Walsh and her colleagues had carried out on the technical side. He adds: “The benefits and the learning from this initiative in the re-use of steel can be applied into lots of other areas because it illustrates that with determination, you can make things that seem impossible work. And we must do it. The first option should always be adapting a building rather than demolition. But that is not always possible. And where it isn’t, cutting embodied carbon is vital and reusing carbon-intensive building materials is a no-brainer.”

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