C2I 2024 Wild Card winner: AVA Bridge & Lift System

Category: Wild Card
Project: AVA Bridge & Lift System
Partners: Network Rail, Expedition Engineering, Walker Construction, Hawkins\Brown, McNealy Brown, ARX, Outokumpu

The UK’s ageing rail infrastructure has always presented a range of challenges for engineers, with swathes of its 19^th Century tracks, tunnels, and stations requiring constant repair, upgrades, maintenance and modernisation to meet the demands of a modern transport network.

One particular headache - and an issue with which UK rail infrastructure-owner Network Rail has been grappling for some time - is the thousands of small and medium sized stations either without footbridges or with structures that are now nearing the end of their operational lives.

In an effort to address this, the AVA consortium, a group of UK engineering SMEs funded by Innovate UK and Network rail, has developed a novel modular footbridge and lift system that is claimed to be greener, longer lasting, simpler to maintain, more cost-effective and easier to install than existing solutions.

Having installed a prototype version of the structure at the Sittingbourne, Kent HQ of consortium partner specialist steelwork fabricator McNealy Brow last summer, the consortium is now getting ready to install the very first public AVA bridge and lift system later this year at Stowmarket Station in Suffolk.

According to the team behind the project which, alongside McNealy Brown, includes main contractor Walker Construction, steel-maker Outokumpu, architect Hawkins\Brown, consultancy Expedition Engineering and the project’s lift designer, “kinetic solutions” specialist ARX - the new system represents a fundamental rethink on the way that bridges of this kind are designed and built.

Whilst traditionally-built footbridges are made by cutting and welding sections of mild steel then painting it, the AVA system has been has been designed with a focus on modern manufacturing methods. Indeed, the entire process is carried out in factory conditions using the kind of state of the art techniques more commonly associated with the precision manufacturing sector, with state of the art fibre lasers and CNC brake presses used to cut and bend components from flat sheets of stainless steel, which are then bolted together into sub-assemblies.

Using this modular approach, the entire structure – including internal cladding, glazing, and other services  - can be fully assembled before the bridge even leaves the yard. It also enables far greater flexibility in layout, meaning that the fundamental design can be reconfigured to meet varying site requirements. 

According to the team, the ultimate vision is for a full “industry 4.0” process, where bridges are built from a stock of pre-fabricated components stored in a warehouse, with a parts list built automatically by an interactive bridge configurator. Any minor customisations could also feed directly from the configurator to the laser cutting and folding process.  

The fact that the system is largely manufactured off-site also vastly simplifies the installation process. Whilst installation of a traditionally built bridge will take 35–40 weeks, the AVA Bridge & Lift System can be fully installed in just 15 weeks. Indeed, only a single 36-hour possession is required to lift in the structure, keeping disruption to rail services to a minimum.  The team has already identified improvements that could get this down to as little as 27 hours for future projects.

One of the keys to the system’s performance is the material used for both the structure and the cladding; a strong, corrosion-resistant duplex stainless steel that requires hardly any maintenance and which extends the design life of the footbridge to 120 years. “What you see today as a finished bridge is pretty much what it will look like in 120 years’ time,” said consortium partner Bob Atherton, from the project’s steel manufacturer Outokumpu. “And at the end of its life, you can pull it apart, recycle it and make another one … it’s 100 per cent recyclable.”

Alongside the assemblies and components of the bridge, the other key element of the overall concept is - of course - the lift: a 21 person “plug and play” system developed by Sheffield firm ARX.

Fully assembled, tested and certified at ARX’s factory this system is installed as a single module with the lift car, drive system, lift doors, cladding and secondary elements all fitted.  According to the team, this means it can be installed in just two weeks, including platform foundations.

ARX has also introduced a number of innovations aimed at reducing maintenance requirements and improving reliability including a dual drive system that provides full redundancy to keep the lift in service, and a decision to install the drive equipment at platform level – rather than at the top as with existing systems - making access easier and safer for maintenance engineers.

Industry response to the new system has been hugely positive. Indeed, an independent assessment carried out on behalf of Network Rail found that AVA surpasses the performance of existing footbridge designs, with lower capital expenditure, and lower cost of ownership. Against this enthusiastic backdrop, the AV consortium is hopeful that the Stowmarket bridge - which opens in just a few months’ time - will be the first of many to grace the network.

In the meantime, the consortium members are already planning further improvements and enhancements to the system including a reduction in the number of parts and bolts, streamlined manufacturing models, weight reduction, constructability improvements, span and height increases, and lift specification enhancements.  The group is also considering applications in non-rail environments such as across roads and rivers and for supporting public infrastructure like car parks, airports and shopping malls.

Looking ahead, the intent is to put forward the AVA Bridge & Lift System as a Network Rail standard design, effectively making it ‘open source’ and available for any designers, fabricators and constructors to deploy an AVA solution on the UK rail network.