Knight Architects has developed a modular bridge for Network Rail that combines practicality with aesthetic appeal.

Knight Architects modular design follows a brief to improve safety at level crossings and provide an alternative to heavy steel footbridges commonly used across the rail network. Flow Bridge is conceived as a visually appealing structure that is not only cheaper and quicker to produce, but also suitable for different locations.

“One of the key challenges for any ‘standard’ bridge solution is how one design can fit a variety of sites,” writes Knight Architects. Standardisation is driven by consistency and repetition, yet good design is traditionally seen as a specific response to context. The Flow Bridge addresses this with contemporary refined forms paired with careful detailing and a human scale. The aim is to ensure that even the ‘base’ design provides an attractive, fitting and welcomed addition to new sites.

To respond to the specific characteristics of a site, the system provides a wide variety of configurations. These extend from geometric adaptability, such as altering the span or width of the deck, through to texture, pattern and colour modifications – all of which are readily achievable with composites.

Diagrams showing the Flow Bridge system, support arches, support location, and deck evolution

While the current prototype – located in Long Marston, Warwickshire – has been built as a stair-only version, the completed system will be capable of providing accessible crossing with the addition of ramps and lifts as necessary. 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.

Smoothing the corner out is important, as it creates a safer, more welcoming user experience. However, doing so can lengthen the bridge, increasing material and land use, as well as cost. The Flow Bridge resolves this with a structural spine that remains orthogonally aligned to the railway while the deck turns smoothly around the corner.

The spine also allows the deck modules to be inserted incrementally, allowing for smaller, more manageable components to be transported and installed, or even replaced if necessary. Added to this, it provides rigidity between deck modules and ensures a precise connection to the concrete-free Rapid-Root foundation system.

Cable management concealed within the spine facilitates safe, accessible and integrated service-crossing of the railway, without the need to add conduit to the outside of the bridge. It also means that the structure can be embedded with structural health monitoring allowing a data-driven approach to bridge analysis.

Traditional solid parapets are eschewed in favour of a glazed system that improves user visibility, safety and enjoyment. At low level the Fibre-Reinforced Polymer (FRP) 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 in place by an aluminium channel.

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.

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