Modular walkway ready to revolutionize level crossing design

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The summary statistics for railway bridges make a sobering reading. It may take a year on site to build one. Only a third of the £ 3-4million that each bridge costs to build is spent on materials and creating the structure itself – the rest is the cost of the contractor and the client.

In addition, the design of the fallback catwalk has not changed for years. In other words, it is visually uninteresting, and the notorious unreliability of standard station lifts makes it far from user-friendly. Despite how long this design has been in use, there has been no attempt to streamline and streamline the way things are done – in some ways the process has become more and more entrenched.

Ripe for disturbance

If any part of the infrastructure sector was ripe for disruption, it was this. Network Rail’s Technical Lead for Buildings and Architecture Anthony Dewar recognized these shortcomings two decades ago and, frustrated with the cumbersome process he witnessed, made it his mission to make things happen. .

Over the past few years, his team has made inroads into the way railway gateways are designed and procured – with Network Rail’s 2018 Gateway Design Competition being the first large-scale intervention – but the imminent arrival of the Ava bridge demonstrator at the Nottinghamshire site signals an even more fundamental change.

The Ava Gateway is a radical modular design developed by a consortium of companies including Network Rail, Expedition Engineering, Walker Construction, X-Treme Systems, MTC, Hawkins / Brown, SCX Special Projects, Norman Foster Foundation and Atelier Ten. The £ 5.4million initiative is jointly funded by Innovate UK and Network Rail.

Network Rail Research and Development Program Manager Janine Fountain agrees that there are cost and schedule issues on conventional projects, a challenge the Ava Project aims to overcome.

The project sparked an innovative elevator design

“The main costs are the planning and execution of the railway assets, the rental of the crane, the transport of the bridge, the obtaining of the building permit, and so on. When the time on site is extended as is the case with the design of walkways, the cost of establishing and maintaining a complex close to the railway line is long and expensive.

Much of the early discussion was about cost and asset disruption, Fountain says. “Our goal is to do that in a single 52-hour possession – maybe even reduced to 48 hours, which is less than a weekend – and we think it’s possible.”

The full-scale demonstrator will be manufactured and erected on a ‘live’ rail test track at Widmerpool in Nottinghamshire later this year to show proof of concept. The structure will then be deconstructed and reassembled for permanent use on the national network. Dewar is reassured that the protester has started some sort of bidding war on regions eager to have a railroad first.

Our goal is to do this in a single 52 hour possession – maybe even reduced to 48 hours.

The term “manufactured” is crucial in relation to the creation of the structure and central to the innovation process.

Rather than being built in a steel fabrication yard from standard sections and then shipped elsewhere to be painted before being transported to site as a full length, the Ava Bridge is designed to be assembled into modules. 1.2 m long using structural elements cut from flat sheets. made of stainless steel and bolted together.

Truss modules can be configured to suit the destination site and fitted with siding, canopy, lighting and other mechanical and electrical (M&E) services before being erected as close to finish as possible .

X-Treme Systems is the manufacturing partner and, as Managing Director Noel Lovatt explains, the company comes to the project with no preconceptions, having never worked with Network Rail before and never built a bridge.

Manufacturing environment

Lovatt’s first task was to introduce the rest of the team to the manufacturing environment, the opportunities in the automation process, and how X-Treme leverages digital technology, along with the relevant constraints such as the size of the leaves.

All the parts needed to form the truss and other elements of the modules will be laser cut from 3m by 1.5m stainless steel sheets, then folded and bolted together. The manufacturing process is good because it is reproducible, says Lovatt, “and much more precise than conventional manufacturing, with tolerances as low as 0.2mm”.

The walkway can be assembled quickly from prefabricated parts

The objective of the project is not only to reduce the investment cost by a third and the construction time by half, but to reduce the carbon over the entire lifetime, to reduce the maintenance demands and therefore the costs. costs, and improve reliability. With a road-tested design approved by Network Rail, the planning and approval stages are expected to be dramatically speeded up.

Improving accessibility is the fundamental goal and with the average cost of a walkway reduced from £ 3.6m to £ 2.6m the number of walkways under construction can be increased without any increase in budget. In addition, the demonstrator will present a new custom-designed lifting basket designed to wipe out the bad reputation of station lifts once and for all.

The Ava Bridge is designed to be assembled into 1.2m long modules

Expedition has been appointed as the engineering consultant for the project and partner Eva MacNamara explains that the team is currently in the process of deepening the detailed design, which needs to be completed as this issue of RCE went to press. “This is the ‘tipping point’ at which the different experiences and knowledge of the team members will come into play,” she says.

The ambitious success criteria forced the team to completely rethink the design and construction of the gateways and to come up with a credible alternative. Saving weight and reducing maintenance were fundamental in this regard, and the switch from standard steel fabrication to a fabrication process using stainless steel sheets addresses both of these issues.

Expedition knew that a modular solution would allow the design to be tailored to any location and facilitate transportation to site for assembly. The use of structural elements made of bent sheet steel significantly reduced the weight of the structure, reducing the foundation and the capacity of the crane. It is also believed to be the first use of preloaded stainless steel bolts on the railroad, MacNamara reveals.

The design has already undergone several iterations with a prototype module produced before the initial design was finalized. While this may seem like a reversal of the traditional project schedule, it is a standard for manufacturing processes where efficiency and optimization are driving forces.

The 1.2 m long modules are configurable according to the location, the number of lanes to be crossed, etc.

The type selection process came up with two options for the final shape – however, these had to be revised afterwards and made ‘less climbable’ in response to concerns from regional Network Rail officials who are responsible for the purchase. of gateways.

One of the project’s biggest technical innovations was the creation of an all-new elevator design – something that wasn’t even planned initially, reveals Dewar.

Station walkways generally use standard elevator technology which is more suitable for high rise buildings. They require a deep lifting pit to house the equipment and must effectively be assembled on site over several weeks. In addition, they can be unreliable, with spare parts to order and high maintenance costs.

The Ava team worked with SCX Special Projects – another newcomer to the rail industry – to develop a “plug and play” lifting platform from scratch. It will be tested and commissioned off-site, requires a very shallow 1.7m deep lifting pit and has 100% redundancy. With standard commercial components and a belt drive system, it can be easily repaired.

Walker Construction CEO Phil Webb says the initiative has been a refreshing change from the normal process he’s used to after more than 30 years in the industry. SMEs are normally “at the bottom of the food chain” with no opportunity to influence the development of a project, he says. “Here we had the chance to influence the design, cost and constructability of the structure. “

Eliminate wet trades

In the track environment, the foundation and substructure are the most complex parts of the project, so a design that eliminates wet looms is a big step forward. A lighter structure that reduces the lifting capacity required is also a big plus.

Construction of the steel screw pile foundations at Widmerpool is expected to start in September with a total four-month construction schedule planned. Webb is confident that it will be reduced to three months once the learning curve is overcome.

The 1.2m long modules are configurable based on location, number of lanes to cross, etc., and MTC is developing a configuration tool that customers can use to visualize how the gateway will adapt to each situation. site.

“We want the design, manufacturing and installation process to be as close to Industry 4.0 as possible,” says Dewar.

He acknowledges that this represents a major leap for the rail gate industry, which he estimates is close to 1.5 behind. Until very recently, only PDFs of “standard catalog” gateways were provided for the supply chain – no CAD drawings and certainly no digital models. Now, says Dewar, the information for each of the new gateways is provided in digital format.

The Ava Bridge consortium is expected to complete its work program by March 2022 in accordance with Innovate UK funding conditions. Webb reveals that the team has already attracted interest from other infrastructure customers, not just those in the rail industry. With the economies of scale that digital manufacturing can offer, the best value will be obtained if they can be ordered in bulk.

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