As materials shortages and rising prices within the construction industry escalate, Network Rail are trying to cope with the problem by investigating new technologies. The government-owned company has been particularly affected by significant increases in the price of steel, Construction News reports.

Chief executive Andrew Haines said: “For us [it’s] about price, we’ve not had real availability restrictions impede us yet. We’ve not had difficulty getting aggregate [and] we are having to make sure we’re planning well ahead but I know from colleagues in other sectors that this is an emerging risk.”

Haines said that as well as taking precautions such as ordering materials such as aggregates early, the company was also exploring alternative technologies. These include two different designs for new footbridges that have been announced recently.

The first one is a modular bridge called Flow, which has been designed by Knight Architects. It is made from fibre-reinforced polymer, which is a lightweight but strong plastic currently used for the manufacture of cars and aircraft. The bridge is specially designed to be installed in days, and it contains no steel or concrete at all, even in the foundations.

The architects explain that the Flow bridge is quicker to produce than a steel equivalent, and can be fabricated off-site, significantly reducing manufacturing costs. The lightweight structure contains a range of modern composites, which can be individually adjusted to suit the location and structural function of the bridge.

The demand for a new style of footbridge was driven primarily to find an alternative to heavy steel bridges which are commonly used on railways. The bridges are also optimised to improve safety at level crossings, in response to a risk reduction campaign by Network Rail launched in 2010.

Traditional level crossings which provide a footpath over the railway are time-consuming and costly to manage, and pose a safety risk to pedestrians, cyclists and horse riders. They rely on users to employ their senses to stop, listen, and look out for trains, and often have inadequate warning systems.

To reduce the number of accidents and fatalities at level crossings, it has been decided to replace the footpath crossings with footbridges. The standard concrete and steel rail footbridge design was heavy, unattractive, and costly to deliver.

Therefore, Network Rail commissioned the design of the new Flow bridge, which is much cheaper and quicker to produce, and adaptable to a range of locations. The visually appealing zero-concrete structure has inclined translucent parapets, which are welcoming and safe, provide views both in and out, and visibility of the onward route.

A second style of modular bridge has also been developed for Network Rail. This bridge is named AVA, and has been created as part of the Transport Infrastructure Efficiency Strategy Living Lab programme.

This is a collaboration between the government and other partners in science and industry which aims to use data, technology, and Modern Methods of Construction within transport infrastructure to make the sector more efficient and cost effective.

The first AVA footbridge will be delivered as a demonstrator over a railway test track at Widmerpool in Nottinghamshire later this year, according to the New Civil Engineer. The structure will then be deconstructed for assembly for permanent use over a rail line.

The project aims to cut capital costs by a third and construction times by a half. It will also reduce the use of whole-life carbon, cut maintenance costs, and improve reliability. The design has already been road tested and signed off by Network Rail, and it is ready to enter the planning and approval stages.

Network Rail programme manager for research and development Janine Fountain explained that there are issues with cost and timescale on conventional projects. She told the New Civil Engineer:

“The main costs are the planning and execution of railway possessions, the crane hire, bridge transport, getting planning permission and so on. When time on site is extended in the way it is for footbridge design, the cost of establishing and maintaining a compound close to the railway is drawn out and expensive.” 

The AVA bridge is designed to be assembled in a single 52 hours, with the potential to reduce down to 48 hours, less than a single weekend, meaning that rail networks would experience minimal disruption. The bridge will be pre-configured to the maximum possible degree, to allow for a swift and efficient assembly process.

Meanwhile, the Construction Leadership Council are warning that the materials shortages will continue well into the second half of next year, particularly timber and steel, which rely on imports.

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