Bridges rank among the most adventurous, beautiful and enduring structures ever to be built. Quite apart from their intrinsic qualities, they capture the imagination thanks to the way they stand in the landscape, crossing roads and railways, rivers, gorges, lakes and estuaries, and now the open sea. Bridge-builders battle with the elements, the fl oodwaters of rivers and the need to carry motor and rail traffi c across valleys at easy gradients.
The story of bridge-building is not just a continuing race to construct ever wider and stronger spans. Many small bridges are equally intriguing and delightful, including arch bridges for pack animals and pedestrians, and ornamental bridges in landscape gardens and parks.
For centuries bridges have been the province of the mason and carpenter, and latterly the engineer in whose work there is an element of art and artistry. The design of bridges, like that of boats, depends in considerable part on the ability to throw a beautiful line. In the twentieth century Fritz Leonhardt, the great Swiss engineer and bridge-builder, wrote: ‘Design has nothing to do with mathematics or calculations. It begins in the brain of the engineer as he starts making sketches with his pencil.’
In recent decades more and more of the most exciting bridges have been created by teams of engineers and architects working together. Norman’s Foster’s famous Millau viaduct was designed with the French engineer Michel Virlogeux, his Millennium Footbridge in London with the engineer Chris Wise and the fi rm of Arup.
Part of the fascination of bridges is that they come in so many forms. There are beam bridges, arch bridges, suspension bridges, cable-stayed bridges, cantilever bridges, trestle bridges. There are drawbridges such as London’s Tower Bridge, lift bridges, swing bridges, tilt bridges and submersible bridges, and transporter bridges which ferry traffi c across water in a ‘gondola’. Then there are the viaducts – fi rst the Roman aqueducts such as the French Pont du Gard in France, continuing with those of the canal age such as Thomas Telford’s Pontcysyllte Aqueduct in north Wales which carries the Llangollen