Carrying keen golfers over the River Tay in Scotland is the Aberfeldy footbridge in Perthshire - the world’s first major plastic bridge - opened in September 1992.
Construction of the bridge was the first successful use of structural plastics in the form of glass fi bre reinforced polymer, but its use came about through necessity as opposed to engineering curiosity.
Client Aberfeldy Golf Club wanted to extend its cramped nine hole course by creating a further nine holes across the River Tay.
The nearest existing crossing was a narrow stone structure built in the 18th century carrying live traffic. As a result, local planners insisted on a separate footbridge on safety grounds.
At the crossing point, the fast flowing river is more than 60m wide, so with normal approaches the bridge had to be more than 120m long, making it an expensive proposition.
Preliminary estimates for a conventional structure in steel, timber or concrete were close to £300,000. The golf club could only aff ord £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.
Harvey planned to make cost savings by having students undertake the preliminary investigation and design work to develop a lightweight bridge that did not need expensive cranes to construct it.
Harvey’s approach to Maunsell was met with an enthusiastic response and a consortium was formed to take the project forward. This included contractor O’Rourke.
Under the overall guidance of Maunsell principal designer Peter Head, 10 Dundee students developed the design for a 63m long main span, with two 25m long side spans.
It was to be a cable-stayed structure with a 2m wide deck designed to withstand full BS5400 loading of 5kN/m2.
The 18m high A-shaped towers and the 112m long deck were built using the Advanced Composite Construction System developed by Maunsell.
The low maintenance, self-coloured glass reinforced polyester components offered many advantages, not least low weight. The cables were also plastic, made up of Kevlar fibres.