Synthetic Wood Solution For Sheffield Bridge

Precision engineering and a synthetic wood system from Japan have given a South Yorkshire rail structure a new lease of life.

Halfpenny Bridge is a single span underbridge carrying a line which serves the Sheffield Supertram and conventional freight traffic over the River Don between Sheffield & Rotherham.

It was strengthened in January 2021 as part of a £1.4m refurbishment scheme which included the replacement of existing timber walkways with FRP mesh.

However, all works were not fully completed after the timber sleepers supporting the track on the single bi-directional line, were subsequently found to be in need of replacement.
 
A further engineering scheme was required so that in the longer-term trams and rail freight could continue to use the line with the minimum of delay.

Two years on and, thanks to a 50-hour blockade, the completed solution has been put in place but, as Senior Engineer Ross Hardy explains, it was not without its challenges.
 
“This was anything but a standard solution,” he said, “and is bespoke in every sense of the word. I personally do not know of anything like it.
 
“Working alongside PBH Rail on behalf of Network Rail, we were asked to design a system for fixing new FFU sleepers to the existing steel deck: in essence they are a form of synthetic wood, manufactured in Japan by Sekasui with a half century design life.”
 
The scheme, designed by Ross, incorporated 15 of the synthetic ‘timber’ panels complete with fabricated steel plates and galvanised tapered packers to accommodate the varying track cant.

“Unfortunately the rail bearers were replacements to the originals and did not run parallel with the main girders, not usually the case. Normally you can rely heavily on archive drawings but, in this instance, there had been so many modifications to the bridge, we simply didn’t have accurate records.   
 
“Allied to this, and because the track was in transition – the cant gradually reducing across the deck – I had to draw a section through every one of the 64 sleepers, an accuracy challenge in itself since the height and position of the supporting railbearers varied with every metre travelled.”
 
Despite all the challenges in the run up to the blockade, the line closure was able to proceed and the complex schedule of work completed ahead of time.

“Sometimes when working with an existing asset, you are presented with many obstacles or constraints that prevent the use of standard design methods. That’s when you have to innovate and genuinely create a new solution.
 
“Hopefully that’s what we achieved at Halfpenny Bridge: a scheme full of challenges but a job well done by so many strategic alliance partners.”

Contractor: PBH Rail
Client: Network Rail