What are the pathways to greater steel reuse in bridges?

“In the race to net zero, if we are to have any chance of slowing down the inexorable rise of global temperatures due to man-made greenhouse gases, the worldwide construction industry must abandon outdated and wasteful practices and adopt circular economy principles
wherever possible.”

The opening paragraph of Steel Reuse in Bridges, a report published in April by Expedition Engineering with funding from The Institution of Civil Engineers, represents a call to action that reinforces growing awareness of steel reuse and its application.

Steel is critical to infrastructure but also represents serious challenges. In its virgin form it is one of the industry’s most carbon intensive materials, while uncertain supply and price fluctuations present further issues. Recognition of these problems has led to efforts to grow the market’s understanding of steel reuse and increased participation in steel reuse by leading stockists Cleveland Steel & Tubes and EMR.

Produced with the aim of adding to that understanding, Steel Reuse in Bridges stresses the case for steel reuse, whose embodied carbon is just 30kgCO2e/t, compared to 330kgCO2e/t for recycled steel and a sizeable 1,750kgCO2e/t for new steel. The report’s opening arguments also note that reclaimed steel is typically £300 per tonne cheaper than new steel, making it about 50% less expensive than new sections.

It goes on to analyse the steel and steel reuse lifecycle to demonstrate how steel can be reclaimed from existing infrastructure assets and the demolition market. Technical, actionable guidance on implementing steel reuse is also included, for example the concept of resource-led design thinking, which utilises available materials as the starting point for design.

Expedition Engineering project director Clotilde Robin led the report with Expedition Engineering principal researcher Hazel Needham, and both drew on research by sister architectural firm Useful Studio’s senior director Catherine Ramsden.

Robin explains how the report’s focus on bridges emerged. “Steel reuse is a discussion that we started a long time ago in this practice. We were seeing a lot of articles about reusing steel in buildings and because of my background as a structural engineer both in bridges and buildings, I was always wondering, why is this not done for bridges? Is there a specific reason and are there reasons that the conditions are more stringent for bridges?”

Seeking answers, Robin and Needham’s research for Steel Reuse in Bridges states that “similar principles can be followed for reused steel in bridge design. However, some key differences between buildings and bridges need to be understood”.

One of the numerous examples of those differences is design life, which is typically 50 years for buildings and 120 years for bridges. Another is fatigue; whereas many buildings are not designed for fatigue, road and railway bridges are. Significantly, footbridges are not typically designed for fatigue, indicating their suitability for steel reuse.

Technical guidance

The report cites relevant guidance documents on designing steel structures with reclaimed components such as: the SCI P427 Structural steel reuse: assessment, testing and design principles guide, the IStructE Circular economy and reuse guidance for designers, and the recently published PD CEN/TS 1090-201:2024 Execution of steel structures and aluminium structures. Reuse of structural steel. SCI P427 Structural Steel Reuse and PD CEN/TS 1090-201:2024 Execution of steel structures and aluminium structures.

Reuse of structural steel, (not yet adopted by the UK as standards) detail the testing procedures required to qualify reused steel, and SCI P427 also introduces amended design procedures.

While both documents primarily focus on buildings, they can also be used for bridges, the report states.

It also notes: “Certification and compliance processes are expected to evolve, shifting toward a testing-based approach rather than reliance on CE or UK marking for individual components.”

It adds that for reclaimed steel engineers should refer to existing guidance on reuse and assessment codes for fatigue life.

Pathways and Case studies

Aside from advice on guidance documents, a key focus of the report was to establish the terminology around pathways for steel reuse, Needham points out.

“When I started researching, I found there was a lot of uncertainty around what people were referring to, so we developed three definitions,” she explains.

Those definitions, demonstrated across a range of case studies in the report, are:

• Whole-span relocation – repurposing entire bridge spans with necessary logistical adaptations;
• repurposed steel – utilising surplus steel from other industries that require recertification;
• reclaimed steel – extracting and reusing steel from existing structures after thorough assessment.

“The first, the reuse of the span, is where you take an existing bridge span and either repurpose it where it is, reuse it where it is, or move that entire span to another location,” says Needham. “There would be small adaptations to that structure, but in principle it looks very similar to how it did originally, or at least the structural form would be very similar.”

The report uses the Lucie Bréard footbridge in Paris – constructed over the Canal Saint-Denis for the Paris 2024 Olympic Games – as a case study. The client was local municipality grouping Plaine Commune, the designer and structural engineer was Schlaich Bergermann Partner; the architect was Explorations Architecture; the steel contractor was Eiffage Métal and the civils and general contractor was Razel-Bec.

The client’s brief specified demolition of two pre-existing structures across the canal, a road bridge and a footbridge, to create a new 5m-wide footbridge with access ramps. The design team proposed reuse of the main span of the road bridge – a 52m-long and 13m-wide orthotropic steel box girder. This was verified for use via a visual inspection and non-destructive tests, which confirmed that it was in good condition and due to a limited in-use service life of only 20 years, was not near the end of its fatigue life.

Repurposed steel, the second pathway, involves steel originally manufactured for a different purpose, says Needham.

“It might be steel produced for the oil industry for example. It wouldn’t come with the normal certificates that structural steel would carry, but you could do all the testing to that steel to demonstrate that it’s acceptable to use.”

Tan House footbridge in Berkshire is also included as a case study in the report. It was commissioned by Network Rail, with WSP as the principal engineer while the designer and structural engineer was Format Engineers, the contractor was Balfour Beatty, the steel fabricator was SH Structures, and the repurposed steel supplier was Cleveland Steel & Tubes.

The crossing is a 53m-long structure comprising a triple-span bridge deck supported by steel-braced column frames with integrated steel stairs at each end of the bridge. Repurposed steel tubes were used for all column elements and their cross-bracings, and the fan members supporting the deck.

The third option, reclaimed steel, entails elements from a dismantled, pre-existing structure such as another bridge or a building, says Needham.

“In those cases, you’ve got a supply of components from an existing structure, and you’d reuse those components once you’ve done the required testing.”

Expedition Engineering and Useful Studio’s own design – Rescued, was shortlisted in National Highways’ Low-Carbon Footbridge Design Contest for the Lower Thames Crossing (LTC) and was among the finalists recognised at an Institution of Civil Engineers event to crown the competition’s winner on 19 May.

Referenced in Steel Reuse in Bridges, Rescued is a modular truss bridge designed for industrial manufacture and repeatability, and achieved a carbon score of A++ SCORBS (Structural Carbon Rating Scheme).

“Ultimately in terms of structural efficiency for this type of span, we converged on trusses as the easiest, most efficient structure,” says Robin.

“A truss can be broken into short elements and can accommodate typical beams sections,” she explains. “It would be more difficult for example to make an arch out of short, reclaimed elements. A truss was also the ideal structural answer for the bridge’s span, to minimise the structure under the deck, and therefore the amount of ramp required to go down to ground level.”

Robin confirms that Rescued was designed to include a minimum 45% of reclaimed steel, equal to around 27t, which would be used for the top and bottom chords of the trusses.

She adds that the steel could be fully reclaimed in the form of UCs [Universal Columns] or UBs [Universal Beams] from the demolition of buildings and sourced through Cleveland Steel & Tubes.

“We specified available reclaimed sections, typically 203 x 203mm or 254 x 254mm UCs. They come in lengths of about 10m to 12m and we would recommend cutting the existing ends, which might be damaged due to their connections during previous use.”

Ramsden adds that the availability of the reclaimed steel elements – researched for sourcing at Cleveland Steel & Tubes – was key to the resource-led design approach for the scheme.

“The name Rescued is about reusing materials informed by resource-led design,” she says. “So, we were looking at using material in its purest form, as close to the condition that we found it in. We tried to design in response to what was available, and we tuned the design response to the sections that we could see were most readily available in the steel supply chain.

“I think that’s the really important point about this process of design thinking; that we’re flipping it on its head. We’re not creating a vision that we then have to seek resource for.”

Bridge to the future

Steel Reuse in Bridges concludes by pointing the way forward for steel reuse, with next steps to focus on reinforcing the business case for steel reuse, gathering further case studies and sharing data to encourage clients, designers and fabricators to explore reuse. It also proposes the creation of a UK bridge database of deconstructed bridges, those in storage, or those scheduled for future demolition, to support a more circular economy.

Robin, Needham and Ramsden add that their experience working on Rescued helped reinforce the importance of collaboration between designers, engineers, and contractors.

They also note the importance of making linkages between demolition specialists and the design community. “It’s about having the contractor on board to demolish in the right way,” Needham says. “In central London areas, buildings need to be demolished slowly and carefully, so there the supply is there, but it’s now about getting the message out and letting people know that this is possible; you can do it within the codes. Once you encourage designers to think more about it, that flows through into the supply chain and drives demand.”

Ramsden adds: “Partnering with demolition contractors is a really important place to go. I think we should start talking to them because we can learn a lot from them. What would help them in disassembly? How would their life be easier and how would they be more inclined to stockpile if we detail things differently?”

This echoes findings from the Alliance for Sustainable Building Products (ASBP)’s Disrupt I and Disrupt II projects, undertaken from early 2022 to late 2024. These initiatives saw ASBP partner with industry body the Institute of Demolition Engineers (IDE) ultimately leading to the launch of ASBP’s steel reuse toolkit in March 2023.

Robin notes that Rescued’s shortlisting in the LTC competition strengthened Rescued as a proof of concept.

“It proved that there is an appetite; we were shortlisted, so that demonstrates that we are on the right track,” she says. She also notes that Cleveland currently has approximately 800t of available reclaimed steel and has advised that it could source more if a pipeline were confirmed. This means around four or five ‘Rescued’ footbridges could theoretically be delivered in the foreseeable future.

Recognition of Rescued and positive initial industry feedback on Steel Reuse in Bridges’ publication confirms that rethinking bridge design with steel reuse in mind is possible. More than that, it is much needed and timely, Robin concludes.

“There is a climate emergency, so we need to be very agile and even a little bit pushy. We can’t do business as usual anymore, and I think it’s really important that we as engineers are disruptive.”

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