img(height="1" width="1" style="display:none" src="https://www.facebook.com/tr?id=2939831959404383&ev=PageView&noscript=1")

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

David Holmes, associate at AECOM, provides supply and fix costs for a range of commercial and industrial doors and windows

AECOM’s David Holmes gives an overview of current costs

Leeds is set for its first £1m penthouse flats in a development that has irked conservation organisations, Manchester is to become surf central, a new Derby performance space is set to replace what will be lost with the Assembly Rooms, and a specialist hospital is to be built in York where once Terry’s made chocolate.

Healthcare, housing and leisure schemes get the green light

Grenfell: Value Engineering - Scenes from the Inquiry leaves audiences shocked and angry at incompetence and indifference that led to 72 deaths

Account of incompetence and indifference leaves feelings of shock and anger

While there’s no doubt the housing market is undergoing huge changes, it’s not all simply due to Covid-19. Brian Green assesses the factors and future outlook

There’s more than the pandemic behind a changing sector

Nancy Sheung’s photographs reveal her hands-on construction experience, indomitable character and promotion of women in unlikely settings

Photographs reveal an unfazed woman in a man’s world