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Uncertain future for historic prototype bridge

Aberfeldy

The world’s first fibre reinforced polymer (FRP) bridge is understood to have closed amid safety concerns.

The Aberfeldy bridge was constructed in the early 1990s when Aberfeldy Golf Club wanted to extend its cramped nine hole course by creating a further nine holes across the River Tay.

Preliminary estimates for a conventional structure in steel, timber or concrete were close to £300,000. At the time the golf club could only afford £100,000 so it turned to the University of Dundee’s civil engineering department for help.

Department head Bill Harvey was aware of work going on at consultant Maunsell’s structural plastics division and conceived the idea that a composite bridge could become a project for final-year students.

Now the unique structure is understood to have closed amid safety concerns.

Local paper The Courier reported Tony Walsh, of Aberfeldy golf club, who said: “We believe the bridge is unsafe and has been for a while. We believe it’s better for the public, and for the golf course in terms of liability, to close it while it is inspected.

“It’s a unique plastic structure and to inspect it is quite complex.

“We would like to work with the community to see if the bridge can be shared with them rather than the golf club having full liability.”

New Civil Engineer has tried to contact the Golf Club and its staff to find out the details of the structural problems.

The Aberfeldy bridge

Completed in 1992, the Aberfeldy bridge was not only the world’s first major wholly advanced composite footbridge, it also holds the title of the longest span fibre reinforced polymer (FRP) in the UK.

The three span cable stayed pedestrian bridge spans has two, 18m high A-shaped towers which support a 64m central section and two 25m long side spans.

The 2m wide deck and parapets are constructed from pultruded glass reinforced plastic (GRP) sections with E-glass fibre and an isophthalic polyester resin.

Even the cables are constructed from 49 fibres of Kevlar sheathed in low density polyethylene.

At 14.5t, the structure is extremely light and therefore required minimal foundations and no craneage when erecting it on site.

A wear resistant finish was added to the deck to give a life to first maintenance of over 20 years. 

Although an inspection of the bridge 17 years after it was built concluded that the primary structure was still in good condition, the parapet had proved less durable than the primary structure. It concluded that weathering of the resin exposing the fibres had highlighted the importance of good specification.

The inspection also found that the connection between the parapet and base had proved inadequate. Other problems included mould and lichen growth visible on the bridge, which it said was due to combination of poor design and lack of maintenance exacerbating the problem.

However there is no evidence that these issues are linked to the current closure.

“Its construction represented a step into the modern world of lightweight high-strength durable materials,” said Tony Gee and Partners executive director Neil Farmer.

“Something not widely known about the bridge is that the cable-stays are formed from lightweight aramid fibres, similar to those used in the manufacture of bullet proof vests.”

Source: www.compositesuk.co.uk

 

 

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