Printable page E-mail this

BRIDGES must always be epic engineering projects involving years of construction work and vast amounts of steel and concrete, right? Wrong. New design and construction techniques mean that bridges can be put together in a matter of days—and they can even be made out of plastic. Consider the InfraCore bridge, a design launched in January by Composieten Team, a firm based in Rotterdam. The designers' goal was to shave months, or years, off the commissioning of new bridges, a process that typically entails lengthy rounds of sketching, specifying and contracting.

Standardising the design and production processes, says Jan Peeters, one of the engineers behind the new design, makes ordering a bridge as easy as buying a car. With a few clicks of the mouse, software adjusts the bridge “recipe” to a client's specifications. The bridge's size, colour, and options such as handrails are chosen on screen, and because engineers no longer need to design each bridge from scratch, the finished product can be delivered within a week. The lightweight plastic even floats, and a two-man crew can install a small bridge in a few hours.

And now, a game from our sponsor Diamonds that are a cut above Google, meet TiVo Home alone Anti-hurricane technology Walk this way A bridge too far? Data with a human touch From dumb pipes to smart sensors Flash and carry Why radio is worth watching The rise of digital radio Biomimetics Biosimulation Lasers Art conservation Electronics How to make (almost) anything Europe's costly new bridges and their builders Jul 29th 2004 Engineering in need of heroes May 14th 1998 Composieten Team, Fiberline Composites

This is just the latest example of the growing use of plastics in bridge construction. Bridges made of fibre-reinforced polymers have been around since the late 1990s, and several hundred plastic bridges now dot the globe, mainly in Europe and North America. They traverse everything from rivers and railways to industrial facilities and highways. Some are even tough enough to support a Sherman tank, as was theatrically demonstrated during the inauguration in 2002 of a road bridge in Shrivenham, England. Its 11-metre deck was made by Fiberline Composites, a Danish firm which, like Composieten Team, makes plastic bridges to order.

Plastic bridges have advantages over both concrete and steel ones. They require minimal maintenance during their lifespans (estimated at over 60 years for the InfraCore), whereas traditional bridges often need a costly overhaul after only a decade or two. Plastic bridges are impervious to common problems such as corrosion, frost, mould and insects, which eliminates the need for special coatings. Adding a new composite deck can extend the life of an old bridge that would otherwise not be worth repairing. And plastic bridges can even be made from discarded coffee cups and detergent bottles: a 14-metre span built over New Jersey's Mullica River in 2002 consists of recycled polyethylene and polystyrene.

Technologically, says Mr Peeters, many of the plastic bridges that are now popping up around the world could have been built ten years ago. It has simply taken time for civil engineers—a naturally cautious bunch who are used to building bridges out of concrete, steel and wood—to come round to the idea of using plastic in bridge construction.

But enthusiasm for plastic bridges is now growing. In November, Fiberline supplied the materials for an all-composite traffic bridge in Klipphausen, near Dresden. Indeed, the former East Germany, notes Finn Jerno of Fiberline, was an unsung pioneer of the use of advanced plastics in construction. Five of Klipphausen's wooden bridges were destroyed in the massive European floods of 2002, and replacing the originals would probably have meant disruptive repair work every ten years. After considering the long-term costs, the mayor decided to build the new bridges using Fiberline's glass-fibre-reinforced plastic instead. The plastic design has another benefit, too: the next time catastrophic weather threatens, Klipphauseners can simply disassemble their new plastic bridges at a moment's notice—and then snap them back together once the storm has passed.