Introduction: What are bridges for?

Mathematical Bridge, Queen's College, Cambridge

Across gulfs and rivers, between peoples and countries, bridges break down separation and foster connectedness.

As far back as we can see in history, human beings have used new technology to solve problems and ease their physical burdens. The distinctiveness of humans as a species is defined by their use of tools, and bridges are technological tools that aim to solve the problem of crossing an obstacle in such a way as to cut down the effort and time needed to do so. The better a bridge is, the less attention the user will need to pay it.

What are the benefits of bridges?

Some of the benefits of bridges are obvious: supplies of food and traded goods can get across an obstacle or through difficult terrain in a shorter time.

'Train passing over Forth Bridge. North British Railway', c.1890-1891

This means that, in economic terms, the cost of travel and trade falls and the financial benefits of increased social cohesion and sharing resources rise. Other longer-term payoffs from easier travel, which is crucially dependent on good bridges, come as a result of increased opportunities to share ideas – intellectual, political and religious.

Today bridges allow easy travel across major rivers and estuaries, over the new obstacles of motorways and railway lines, and between neighbouring islands. International trade and travel depend on shipping and air routes, but efficient distribution networks depend on bridges.

Island-hopping using bridges. The Kojima Sakaide route, Japan

What will I learn in this module?

We have already mentioned some of the 'whys' of building bridges, but the bulk of this tutorial will address the 'hows'. How can a load be supported when crossing a gap; how can basic designs be adapted, using new ideas and new materials to extend the reach of a bridge; how can functionality be retained while the form of a bridge is made more pleasing?

Some of the bridges you will meet in this tutorial are delicate, ingenious and innovative; others are sturdy, functional and – frankly - dull. Each of them is the end-product of centuries of mental ingenuity coupled with constant technological development, of imagination held in check by the need for safety, reliability and peer approval.


Juscelino Kubitschek Bridge - the Brasilian 'wave' arch.

Next time you see a bridge, we hope it will be with a fresh sense of understanding - and perhaps a greater level of appreciation