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Complex bridge project benefits from BIM

The new Stockingfield Footbridge, which has been designed to connect three communities and provide residents with easier access to greener spaces, has been built using the latest digital technology has to offer in modern infrastructure design.

Located in the Maryhill area of Glasgow, the new Stockingfield Footbridge is a twin span cable stay structure designed to provide access across the Stockingfield Junction on the Forth & Clyde Canal. 

As well as reconnecting three communities, it will also provide the last linkage in the canal towpath. 

In addition to two curved bridge decks, the structure features a viewing platform, taking advantage of the site’s elevated view, underneath a focal 34-metre-high inclined tapered mast.

Designed by Jacobs and delivered by main contractor Balfour Beatty for client Scottish Canals, with funding from Sustrans and the Glasgow City Council Vacant Derelict Land Fund, the bridge and wider connectivity project has been borne from community engagement and is part of a long-term partnership between Glasgow City Council and Scottish Canals.

SH Structures were responsible for modelling, fabricating, supplying and assembling the mast, twin decks, access ramps and stairs/balustrade system that formed the completed bridge structure, using a combination of Trimble’s constructible modelling software and hardware to deliver the works. 

The firm used Tekla Structures 3D detailing software and Trimble SX10 – a scanning total station that combines surveying, imaging and high-speed 3D scanning in the one instrument – coupled with a TSC7 controller.

Martin Selby, senior CAD technician at SH Structures said the Stockingfield Footbridge project was particularly special for many reasons, providing a chance to work with Scottish Canals, who they've developed an "excellent relationship" with. 

"Bridges are always unique, especially those which have been carefully considered and designed to create a legacy for the communities who use them," said Selby.

“Complex projects inevitably present a wide range of challenges and bridges of this scale are no exception. 

"Perhaps our main challenge on this particular job was to develop a design that would give the required connection across the canal junction; getting something to work structurally that would cope with the complex dynamics and site topography, whilst also fitting into the congested site. 

"Maintaining the required clearance under the bridge and the required slope of the ramps, while simultaneously tying into the alignment of the towpaths was also a major headache at the initial stages. 

“All of this resulted in a complex geometry where most of the deck section soffits were twisted plates."

He added curving steel in one direction is a "relatively simple process" but this project involved curving it in two directions, which was "definitely more of a challenge". 

"It’s these areas of complexity where the 3D visualisation offered within Tekla is so valuable, enabling us to offer our client a fully rendered model, containing all of the materials – a model that can then form a central part of discussions,” Selby explained.

“Thanks to the software integration, we were able to export the completed Tekla model as an IFC file and import this directly into the SX10. 

"This gave the engineering and site team full access to the accurate model data and 3D coordinates at any given point on the bridge structure, all of which proved vital when it came to setting out on site. 

"Not only were we able to check that the dimensions and geometry were correct as assembly progressed, we were also able to verify the movements of the deck profile and mast as the cables were being tensioned."

The size and complexity of the bridge meant various sub-assemblies were constructed using temporary works on a designated part of site. 

"With three bridge sections - all of which had to come together at one central point before being welded into place - and the foundations and bearing points already having been installed by the contractor, everything had to align perfectly," Selby said. 

"We were working to some extremely tight tolerances. 

"Here, setting out using the SX10 and 3D model coordinates helped to ensure all went ahead smoothly on site.”

SH Structures pushed the data flow between Trimble’s BIM software and its site hardware even further. 

Having imported the IFC file into the SX10 device and using the SX10 camera, the team were able to view a live overlay of the model in the context of the real-time site.

Robert Binks, project manager at SH Structures, said: “This capability proved extremely helpful, ideal for checking and verifying that everything was lining up and in the right position – it really provided us with additional peace of mind. 

“Being able to flip between live images and the 3D model gave a nice, visual representation of what you were currently seeing on site compared to the final end-goal.”

SH Structures’ work on the Stockingfield Footbridge project saw the steel fabricator win Infrastructure Project in the 2022 Tekla Awards, with the judges praising the project as a great example of how to execute a Trimble model to field. 

If you would like to contact Sarah Walker about this, or any other story, please email sarah@infrastructure-intelligence.com.