Network Rail has unveiled an extraordinary bridge design that has the potential to completely transform rail crossings across Britain. This ground-breaking circular bridge, which was recently showcased at the NCE's Future of Bridges conference, is poised to revolutionise the way footbridges are constructed over railway tracks. With its lightweight materials, this bridge not only prioritises environmental sustainability but also offers a modern, modular design that can be flexibly adapted to different locations. What's more, the bridge comes equipped with built-in monitoring capabilities to effectively assess usage patterns and maintenance requirements.
In Spring 2020, Network Rail enlisted the expertise of Knight Architects to develop the concept design, fostering a collaborative effort that involved remote cooperation with a diverse array of companies, including Jacobs, KS Composites, Sui Generis, Q-Railing, Rapid Root, Epsilon Optics, Sentry Systems, and Mabey Bridge. Andy Cross, the Program Manager at Network Rail, emphasised the advantages of working with such a range of partners, stating, "This approach allowed us to form partnerships with several small and medium-sized businesses, many of whom hadn't previously been involved in railway projects but possessed the necessary skills and expertise to bring the concept of a lightweight, cost-effective footbridge to life. In just 11 months, we have successfully developed a breath-taking prototype bridge that not only meets stringent environmental standards but can also be efficiently installed in a matter of days, thereby minimizing disruption for the surrounding communities."
At present, Network Rail's only viable option for constructing or replacing footbridges is the standard non-station footbridge design, characterised by its cumbersome nature, lack of visual appeal, and exorbitant costs. In sharp contrast, the newly introduced design capitalises on the use of Fibre-Reinforced Polymer (FRP), a lightweight material extensively employed in industries such as aerospace and automotive manufacturing. This choice of material not only imparts remarkable strength but also significantly reduces transportation and installation expenses.
The ultimate aspiration for this ground-breaking bridge design is its widespread adoption throughout the country as part of an extensive program aimed at transforming the construction of footbridges across the entire rail network. Moreover, it presents an appealing alternative to repairing existing crossings. Moving forward, the project's next phase involves the development of sustainable procurement and construction options, alongside the creation of a ramped version of the bridge to cater to diverse accessibility needs.
The prototype has already undergone successful construction and testing at a facility in Long Marston, Warwickshire, and is currently being showcased at the prestigious 2021 RAIL Live event.
Key Design Aspects:
The Corner: Traditionally, the positioning of ramps and stairs at a 90-degree angle to the main span, coupled with high-containment parapets, has resulted in a "blind corner" situation that can be uncomfortable for bridge users. To address this challenge, the "Flow" Bridge incorporates a structural "spine." While the deck elegantly turns around the corner, the supporting spine remains orthogonal to the railway alignment. This deliberate separation between the spine and deck enables a seamless flow around the corner while preserving a minimalist structural footprint. Furthermore, the spine facilitates the incremental lifting and installation of smaller deck modules, allowing for enhanced flexibility and ease of transportation.
The Parapet: Railway containment regulations often necessitate solid, towering parapets, creating an enclosed and tunnel-like experience for users, limiting views and contributing to feelings of unease. In response to these concerns, the design team sought to reintroduce enjoyment and openness to bridge crossings, offering new perspectives and vantage points for appreciating the surrounding environment. To achieve this, a glazed parapet system was meticulously developed. At the lower level, the composite material extends above the deck to meet structural requirements, while the containment aspect is achieved through laminated frameless glazing, securely held in place by an aluminum channel. This transparent element not only enhances safety by providing a clear line of sight along the entire route but also instils a sense of security in users. The glazed parapet system offers a multitude of options tailored to diverse site conditions, including a layered glass/composite solution specifically designed to bolster durability in areas prone to vandalism.