GRP bridge offers plastic construction promise

Words:
Stephen Cousins

Post-tensioned modular structure raises architectural potential

Arup GFRP modular bridge at Aristotle Lane site
Arup GFRP modular bridge at Aristotle Lane site

The technology behind the world’s first modular glass-fibre reinforced plastic (GRP) bridge could open up exciting new possibilities for architectural design, its engineers claim.

The post-tensioned bridge, launched by design consultancy Arup and bridge specialist Mabey, is 70% lighter than steel and designed for assembly at locations with restricted access for large cranes or heavy machinery.

The system comprises identical 1m-long modules that are fixed together with bolted shear connectors, then post-tensioned to enable spans of up to 30m.

Ian Wise, structural engineer at Arup, told RIBAJ: ‘Our system could be suitable for building lightweight roofs, or even ambitious bespoke pieces of architecture. The variety of geometry and types of form that can be created is almost unlimited. It’s also possible to tailor the materials and fibres to alter texture and stiffness.’

The variety of geometry and types of form that can be created is almost unlimited. It’s also possible to tailor the materials and fibres to alter texture and stiffness

The first bridge to be built using the technology (being marketed by Mabey as Pedesta) was installed at a Site of Special Scientific Interest for Network Rail in Oxford, England. The modules were light enough to be transported on an articulated lorry, then assembled on site and lifted into position from a distance. Modules only require a pallet truck or forklift to move, making installation faster, safer and more efficient.

The key innovation behind the bridge concept is the combination of GRP, smaller module sizes and the post-tensioned structure. ‘Traditionally, if you wanted to build a 20m long bridge in GRP you would have to make a 20m-long mould then infuse it with resin,’ says Wise.

GFRP post tensioned modular bridge
GFRP post tensioned modular bridge

‘If the process went wrong you’d have to bin all the materials and start again and entirely different moulds would be required for different projects. Creating small modules makes tooling cheaper and puts less material at risk.’

In addition, post-tensioning the structure simplifies connections between modules as they are only required to withstand compression forces. The structure is stiff enough to prevent contortion, an issue that can affect plastic structures, and could last over 100 years. Wise comments: ‘The only aspects of GRP that can degrade over time are from UV radiation and water ingress on exposed edges, which de-bond fibres from the resin, but these are fairly easy to manage by applying a coating.’

The modular bridge concept was developed by Arup and part-funded by the UK Rail Safety and Standards Board. Mabey is the first licensed distribution partner.


 

Latest

If passive heat control can work in Burkina Fasso it can surely be applied in Europe. Brian Ford offers seven design principles to help avoid carbon intensive air conditioning

Air conditioning makes us hotter – don’t give it house room

South Africa’s housing crisis puts the UK’s in the shade. Joseph Noero takes a practical approach to his mission to change that

Simple, affordable Table House has huge potential to improve lives

RIBA Royal Gold Medal winner famed for buildings such as the Olivetti offices, Fountains Abbey visitor centre and the Downland Gridshell among others; teacher, collaborator and known above all for his inclusive, optimistic approach

Hugely influential designer, teacher and Royal Gold Medallist

Architect Tom Bennett explains why the urgency of arresting climate crisis leaves him no alternative but to get involved – seriously

One architect on why climate activism is worth a criminal record

Profits flatline in the RIBA Business Benchmarking 2019 survey despite bigger workloads for architects bringing in more revenue

Employment is up, so is international work – the results of RIBA’s Business Benchmarking survey