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Longest ever single beam composite bridge uses carbon fibre-reinforced polymers (FRP) to compete with traditional concrete and steel alternatives

Huntsman Advanced Materials (Basel) : 30 March, 2011  (Application Story)
Acciona Infrastructure invited Huntsman, which has supported Acciona In a number of construction projects in the specification of resins and structural adhesives to be part of the HP FUTURE-Bridge project. Co-funded by the European Commission under the 6th Framework Programme of Research, this project ran from October 2006 to September 2009.
Longest ever single beam composite bridge uses carbon fibre-reinforced polymers (FRP) to compete with traditional concrete and steel alternatives
The overall objective of the HP FUTURE-Bridge project was to develop a new high-performance and cost-effective construction concept for bridges based on the application of carbon fibre-reinforced polymers (FRP) to effectively compete against conventional bridges made from concrete and steel. Carbon composites have been used in Aerospace and Marine applications for over 50 years and are now increasingly being considered for use in bridge structures around the world. Within the consortium, Huntsman played a key advisory role, sharing knowledge and expertise on maximising the potential of carbon composite bridge designs with structural adhesives and resins.

In a recent project, Acciona has been working with Huntsman to construct a composite pedestrian bridge in Madrid, over the Manzaneres River. Because it was to be erected over a river, the bridge needed to be made from one monolithic single piece. The challenge therefore lay in designing a load bearing, jointless, single structure that was also light enough to meet the transportation, logistics and installation requirements defined for the project.

As the installation site was in the city centre, space limitations and the need to limit disruption meant the constructors were allowed a maximum of four hours to mount the bridge onsite. It was imperative that the bridge was designed to be as lightweight as possible.

To achieve a weight which would assist Acciona with meeting the installation timescales while realising high levels of endurance and performance in constructing the single, jointless 44m long bridge beam, the engineers used a range of Araldite products.

Araldite LY 1564 / Aradur 3486, which is specifically designed for thick laminates manufacturing, was tested in the preliminary infusion trials and then used in the production of the single beam through an injection infusion process. Offering excellent physical properties such as low viscosity, the long pot life of 520-620 minutes at 23C also proved particularly beneficial in producing large sections of the beam in a time-effective manner.

Araldite LY3505 / XB 3403 and XB 3404-1, a composite resin system designed for the production of high performance composite parts and moulds using a wet lay-up process has been used to fill and reinforce the prefabricated ribs of the bridge.
The ribs have been bonded to the beam with Araldite AW 4856/HW 4856, an epoxy adhesive system with enhanced toughness, chemical thixotropy and low exotherm for large composite parts. Its physical properties allow usage in applications requiring load bearing strength and excellent adhesion under adverse application conditions. Heat and chemical resistance offered by this system adds to the anti-corrosive properties of the single beam. These features make composite bridges better suited for installation in locations that experience adverse weather conditions in comparison to their conventional counterparts.

“We needed a thick laminates manufacturing system offering good fluidity and permeability and a bonding solution with extremely reliable adhesion,” said Anurag Bansal, Head-Manufacturing, Infrastructures Area, Acciona R&D Centre, commenting on the choice of Araldite system. “When it came to selecting the best adhesive to use, the decision was simple. Araldite AW 4856/HW 4856 was chosen because of its exceptional track record in providing excellent adhesion properties for large composite parts such as wind blades and boat hulls. Adding to this, the characteristics of Huntsman’s resins meant we could apply them evenly and in a time and cost-effective manner, meaning the finished quality and performance of the bridge was improved and all importantly, manufacturing times were shortened as well.”

From the initial fibre placement through to the demoulding and finishing processes it took a total 30 days to manufacture the bridge. This is the first time in the history of the Composites Industry that a 44m long, 3.5m wide, structural load bearing bridge beam has been built utilising 12 tonnes of carbon fibre. The surface of the beam is smoother and more aesthetically pleasing than a steel or concrete bridge. In offering excellent corrosion resistance, less maintenance and no painting is required.

If the pedestrian bridge had been made from concrete or steel, this would have resulted in an extremely heavy beam weighing at least 50 tonnes, whereas the carbon composite beam is only 25 tonnes.

The bridge was installed in less than 2 hours using a 75 tonne crane. By comparison, steel and concrete bridges typically take a minimum of 6 hours to install, using a 300 tonne crane. The significant weight saving created by the single composite beam allows smaller cranes to be used, providing an easier, faster and more economic installation process. Because no joints, assembly or high capability cranes are needed for either installation or maintenance, not only does the single beam afford more architectural freedom in design it also reduces onsite plant requirements and opens up installation opportunities in a host of different locations.

“By offering huge potential to produce more efficient and cost-effective structures, carbon composites could truly revolutionise the construction of long span bridges. They will also dramatically increase durability, reducing through-life costs and disruption due to reduced maintenance requirements. As early pioneers, we’re proud to be at the forefront of this new era in bridge design, allowing innovative and more efficient structural forms to be conceived and constructed,” added Stefano Primi, Head-Infrastructures Area, Acciona, R&D Centre.

The footbridge opened at the end of 2010 and is now used by approximately 1500 people on a daily basis. Acciona is currently constructing a 200m long single beam bridge in Cuenca (Spain). The company also has plans to further explore the usage of composites in construction across Europe, with a longer term view to undertake similar projects on a global scale.

In partnership with Huntsman, Acciona has won the Civil Engineering category of the JEC Innovation Awards 2011, receiving the award in recognition of the innovative use of composites in construction.

Acciona Infrastructure is a global leader in infrastructure development and one of Spain’s largest corporations with activities in more than 30 countries. The company covers all aspects of construction, from engineering to project execution and maintenance. This includes the management of public works awards, especially in the area of transport and building construction.

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