A new design of bridge that could transform rail crossings across Britain has been unveiled by Network Rail.
The innovative circular bridge is set to revolutionise the way Network Rail builds footbridges over the tracks.
Made from lightweight material, the environmentally friendly bridge can be installed in a matter of days, and its modern, modular design means it can be adapted to different locations. It also features built-in monitoring to assess usage and maintenance needs.
Knight Architects was appointed to develop a concept design in Spring 2020, and have developed the design almost entirely remotely with Network Rail, Jacobs, Flo Flo, KS Composites, Sui Generis, Q-Railing, Rapid Root, Epsilon Optics, Sentry Systems and Mabey Bridge.
Network Rail programme manager Andy Cross emphasised the benefits of working with a range of companies.
“We were able to take a different approach,” he said.
“This has allowed us to work with several small and medium-sized businesses, many of whom haven’t worked on railway projects before but have the skills and expertise to bring the concept of a lightweight, low-cost footbridge to life.
“In just 11 months we have developed a prototype bridge that is stunning in design, environmentally friendly and will take days and not weeks to install and thereby causing less disruption for the surrounding community.”
Network Rail currently has just one option when considering building a new footbridge or replacing an old one, the standard non-station footbridge design that is heavy, unattractive and expensive to deliver.
This new design is made from Fibre-Reinforced Polymer (FRP) – a lightweight material that is widely used in other industries, including the manufacture of aircraft and cars. The material is very strong but lightweight, leading to lower transport and installation costs.
It is hoped the ground-breaking design will be adopted across the country as part of a wider programmer of work to transform how footbridges are built on the rail network in future, as well as providing an attractive alternative to repairing existing crossings. The next phase of the project involves developing sustainable procurement and construction options as well as a ramped version of the bridge.
The prototype has been trial built at a test centre in Long Marston, Warwickshire, and is on show there at the 2021 RAIL Live event this week.
Traditionally, ramps and stairs are positioned at 90 degrees to the main span which when combined with high-containment parapets creates a ‘blind corner’ to turn around. This creates an uncomfortable moment for users, unable to see who or what is around the corner. Smoothing this corner out is important, as it creates a much safer, more welcoming user experience. However, doing so can lengthen the bridge, pushing the stairs/ramps away from the rail fence line and clearance envelope. This increases the cost, material use, and the land required for crossings.
The ‘Flow’ Bridge resolves this with the addition of a structural ‘spine’. Whilst the deck turns smoothly around the corner, the supporting spine remains orthogonally aligned to the railway. This ‘disconnect’ between spine and deck allows the deck to ‘flow’ around the corner, whilst maintaining a minimalistic structural footprint.
The addition of a spine also unlocks other benefits. On site, it allows deck modules to be lifted in incrementally, allowing for smaller, more manageable components to be transported and installed, or even replaced if necessary. It provides rigidity between deck modules, resulting in more refined connections, and allows precise connection to the concrete-free ‘Rapid-Root’ foundation system.
The containment requirements of the railway often lead to solid, tall parapets, which create an oppressive, tunnel-like experience. The view from the structure is restricted, and the resulting enclosed space being poorly overlooked can even feel unsafe. In response to this, the team wanted to return bridges to being enjoyable ‘moments’ within a walk, opportunities to take in a new view, a vantage point from which to experience the surrounding environment.
But this is also about safety – the view of the bridge is also opened up, and with more visibility of who is on the bridge, people can see their entire route before they embark upon it. Knowing that they can be seen on the bridge will make people feel safer when using it.
Opening up these views requires transparency, and so a glazed parapet system has been developed. At low level the composite material extends up above the deck, but only as far as is necessary from a structural standpoint. Beyond this, the containment is achieved through laminated frameless glazing, held by an aluminium channel; a system designed by Q-Railing.
The glazed element is one of the ‘variables’ of the scheme, with a multitude of options available to suit all site conditions. For example, a layered glass/composite solution has been developed to improve the glazing durability in sites particularly prone to vandalism.
Department of Civil EngineeringDepartment of Civil Engineering – International Burch University (ibu.edu.ba)