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Stunning Helical Footbridge Spans the M8

Harthill Helical footbridge during installation

Harthill Helical footbridge during installation - Photo by SH Structures

Harthill Curved Steel Footbridge - Photo by Ramsay McIver

Harthill Curved Steel Footbridge - Photo by Ramsay McIver

Helically wound tubes - Photo by James G Anderson

Helically wound tubes - Photo by James G Anderson

Harthill Footbridge during fabrication at S H Structures

Harthill Footbridge during fabrication at S H Structures

In excess of 15,000 highway bridges in the UK form an essential part of the transport infrastructure, with around 300 new or replacement structures being built each year.

As part of a £5 million investment the new footbridge at Harthill Service Station over the M8 in North Lanarkshire adds not just an essential bridge but also an architecturally stunning one.

Whilst replacing the original bridge, which was constructed in 1965, Harthill was also extensively redeveloped to provide two new service stations and a local public transport interchange. This provides a vital link between the eastbound and westbound sides of the M8 and encourages people to use the improved public transport links into Glasgow and Edinburgh which in turn reduces traffic into both cities.

After an initial study looked at various options the decision was made to use a helical truss system which would allow the 90 metre span to be bridged with ease.
A helical truss form offers many benefits when it comes to bridge design. The open framework results in elements being primarily in tension or compression, to create a very light but stiff form of construction, and in the instance of the M8 footbridge, an aesthetically pleasing and impressive final structure.

Twelve 'strands' wind around the outside of the structure to create the signature corkscrew-like appearance containing an enclosed crossing which is fully glazed with polycarbonate panels, ensuring a safe and comfortable environment for pedestrians and cyclists using the bridge to cross the motorway.

The strands were curved by Angle Ring at their extensive production facility in the heart of the UK.
Over 2500 metres of steel weighing in at over 128 tonnes were curved by Angle Ring with the main helical bends comprising of more than 98 tonnes of 168.3 diameter CHS (circular hollow section) ranging in thicknesses from 12.5mm up to 40mm thick.
Although Angle Ring does offer multiple processes at their Midlands production facility, including Hot (Induction) bending, all the sections were curved using a cold rolling process.

Tim Burton of SH Structures, who prefabricated the hollow sections for the bridge in seven sections off-site before they were delivered to Harthill, stated
"This ability to carry out a large amount of fabrication and assembly off-site, is clearly one of the many benefits of using steel and enabled the project to be safely delivered on time with the minimum disruption to the general public and road users.”

Erection of the main span was carried out by SH Structures using one of the UK’s largest mobile cranes complete with a 90 metre jib and 600 tonnes of superlift counterweight.
The crane lifted the 230 tonne superstructure element of the footbridge into position over the M8 using a single operation meaning the motorway was closed for less than 7 hours ensuring minimal disruption.

Mark Phillips who project managed the work at Angle Ring commented "We have worked on hundreds of bridges over our 60 year history but without doubt the helical frame of this is certainly eye catching and is a superb showcase for our metal bending services".

A video showing the lifting of the bridge is on youtube:

Many thanks for the photography to:

James G Anderson
Flickr ID: jamesganderson1979

Ramsay McIver @ Caiyside Imaging Ltd
Flickr ID: Ramsay

S H Structures Ltd

For more information about Angle Ring please contact our sales team
Tel +44 (0) 121 557 7241
Fax +44 (0) 121 522 4555

Client: Transport Scotland
Concept designers: Scott Wilson
Main contractor: Raynesway Construction
Steelwork contractor: SH Structures
Steel Bending Engineeers: The Angle Ring Co
Structural Engineer: Buro Happold
Project value: £5 million
Bridge Span: 90 metres
Total Curved Steelwork: 128 Tonnes

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