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Modern high-strength composite materials present ample opportunities for energy-efficient solutions with lower environmental impact and reduced through-life costs for the rail infrastructure. Network Rail, the UK’s rail network owner, has partnered with the National Composites Centre (NCC) in Bristol, UK, a world-leading research hub developing state-of-the-art materials and technology, to explore new design concepts for using composites in the rail industry.
Growing population and expanding urbanization worldwide require more sustainable mobility solutions to tackle global resource scarcity and climate change.
As one of the most sustainable transportation modes, rail-based transport systems are taking an ever-increasing share of the mobility demand. According to the International Transport Forum (ITF) Transport Outlook 2019, the global passenger transport demand will more than double, and freight transport is expected to triple in the next 30 years.
Growing Passenger Demand Requires Advanced Rail Infrastructure
Composite materials are already playing an increasingly important role within the transport industries due to their lightweight nature, durability, and low environmental footprint. Composites offer significant improvements over traditional materials and provide innovative and sustainable solutions for various critical infrastructure projects.
Many countries, either with well-established or rapidly growing rail networks, are exploring modern composite materials that can lead to the wide-scale infrastructure improvements necessary in the rail industry.
The benefits of using composites in the rail industry to reduce the infrastructure lifecycle costs can be substantial, considering that the US rail network consists of nearly 140,000 miles of track and more than 100,000 bridges, all requiring continuous upgrade and repair. Network Rail in the UK conducts more than 10,000 annual inspections of the timber, concrete, and steel structures critical for the integrity and reliability of the rail transport system in the country.
Innovative Composite Footbridge as a Technology Showcase
A prototype composite footbridge named “Futura”, designed by Marks Barfield Architects (London, UK) and COWI (an engineering consultancy group based in Lyngby, Denmark) is being developed. It will demonstrate the benefits that could be gained by using lightweight and durable composite materials for both new-build and replacement structures in rail infrastructure.
The concept footbridge components are being manufactured in the NCC's facility in Bristol by using modern high-precision manufacturing methods, allowing rapid and straightforward precision-fit assembly on-site with minimal disruption of the rail network operation, road traffic, and local businesses.
High-Performance Composite Materials Enable Cost-Effective Rail Infrastructure
The prefabricated large-scale parts will be molded from fiber-reinforced plastics (FRPs). FRP is a composite material consisting of a polymer matrix reinforced with fibers. The fibers can be made of glass or carbon, and in some cases, paper or wood fibers can be used in biodegradable composites. The polymer matrix in the modern composite materials is usually an epoxy, vinylester, or polyester thermosetting plastic. FRPs are extensively used in the aerospace, automotive, marine, and construction industries.
The main advantages of using FRP composites in rail infrastructure arise from the material's high strength-to-weight and stiffness-to-weight ratios, compared to conventional construction materials such as steel and reinforced concrete, resulting in lightweight final structures.
FRPs have excellent corrosion and weather resistance, making them suitable for long-lasting structures with reduced maintenance. NCC's latest technology and know-how enable cost-effectively fabricated FRP components that comply with stringent fire, smoke, and toxicity standards for a wide variety of rail infrastructure applications.
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Network Rail Embraces Durable Composite Solutions
The first self-supporting FRP bridge in the UK was installed at St. Austell in October 2007 by Network Rail and was designed by Parsons Brinckerhoff (now WSP), followed by Network Rail’s first all-composite station footbridge installed at Dawlish in 2011 (designed by Tony Gee and Partners LLP, UK and manufactured by Pipex, UK).
The new innovative composite footbridge design features easily adaptable components manufactured off-site that can be assembled into several standardized structures to fit different platform architectures.
The technology will allow building replacement infrastructure that aesthetically replicates the character of the original steel or concrete structures, at the same time providing much lighter and more durable solutions.
Wider Adoption of Composites in the Rail Infrastructure
In perspective, this approach will enable composite material innovation that can be transferred to the broader rail infrastructure, including walkways, station platforms, and railroad gantries.
The non-magnetic and non-conductive properties of the composite materials make them particularly suitable for the fabrication of handrails, fencing, and third rail covers for the British rail network, where overhead lines and the third rail systems account for around 40% of the entire rail network, minimizing the risk of fatal electric shocks.
A Pathway Towards Next-Generation Composites in the Rail Industry
When considering the energy and material resources involved in the manufacturing process, it appears that the cost of the FRP components is high in comparison to conventional steel, whether considered per unit weight or based on force-carrying capacity. However, the direct and indirect benefits associated with the use of FRP composites in the rail infrastructure, such as rapid assembly from large-scale prefabricated components (less labor demanding), longer life cycle, and reduced maintenance costs, reveal the competitiveness of modern composites over the conventional construction materials.
Starting with this composite footbridge design, Network Rail, in collaboration with its partners, aims to develop a sustainable low-carbon supply chain for infrastructure projects that would increase the use of composites in the rail industry following the company's strategy for reduced cost and greenhouse gas emissions.
References and Further Reading
NCC (2020) NCC partner with Network Rail. [Online] www.nccuk.com Available at: https://www.nccuk.com/news/ncc-partner-with-network-rail/ (Accessed on 29 September 2020).
E. Doran (2020) NCC, Network Rail join to construct composite footbridge. [Online] www.compositesworld.com Available at: https://www.compositesworld.com/news/ncc-network-rail-join-to-construct-composite-footbridge (Accessed on 29 September 2020).
A. Morby (2020) Network Rail to prototype composite station bridges. [Online] www.constructionenquirer.com Available at: https://www.constructionenquirer.com/2020/09/16/network-rail-to-prototype-composite-station-bridges/ (Accessed on 29 September 2020).
ITF (2019) ITF Transport Outlook 2019, OECD Publishing, Paris. Available at: https://doi.org/10.1787/transp_outlook-en-2019-en.
Kurzina, E.G., Kolmakov, A.G., Aksenov, Y.N. et al. (2019) Comparison of the Composite Materials Intended for Damping Elements for the Infrastructure of Rail Transport and Rolling Stock. Russ. Metall. 4, 448–452. Available at: https://doi.org/10.1134/S0036029519040232
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