In recent years there have been a disturbing number of bridge collapses in North America. Ageing infrastructure and tired concrete can, to a certain extent, be blamed but the real cause lies in our having forgotten how to build for the millennia.
The remains and ruins of the ancient world tell us a simple story. If you build with arches your works will remain. The Romans, inventors of concrete and fanatical builders, identified the importance of the arch in construction and many of their works remain standing two-thousand years later. The Coliseum, in Rome, is supported by a series of interlocking arches. The Pantheon, also in Rome, is a gentle arch constructed with varying strengths of concrete to distribute the weight. Even the non Roman, Leaning Tower of Pisa remains leaning while standing thanks to its pattern of interlocking arches.
Roman roads survive today thanks to the curve, or camber, in their surface. Every modern road has a similar camber in order to enable drainage and allow the road to last longer. Curves carry the load and keep structures intact. When we look at pre-Roman civilisations we generally see remains that are merely vertical. Columns without roofs.... because they chose to park the horizontal on top of the vertical and this configuration cannot stand the test of time.
Suspension bridges are supported by inverted arches. Medieval cathedrals still stand today thanks to the counterbalanced, load carrying, ‘flying buttresses' on either side which are nothing more than arches cut in two.
In North America it has become customary to build for a lifespan of forty years or so. The autocratic ancients could build for two-thousand years or more but the moderns have elections every four or five years and this leads to building for the next election rather than for the future.
In North America, there is a tendency to build with concrete both vertically and horizontally. But, while concrete is amazingly strong and long-lasting in the vertical (consider the concrete – stone faced – Roman Coliseum) it is not good in the horizontal and tends to tire and collapse – with predictable deadly consequences.
To make our concrete bridges safer and longer lasting, we need to return to building with arches. Arches can be integrated into new construction or they can be added to existing bridge structures. Why not add pre-fabricated arches or semi-arch support structures to existing bridges to prolong their lives for a hundred years or more.
We all know that the circle is the defining characteristic of our lives and it is hardly a stretch to recognize that a part of the circle, the arch, is the most effective support for the part of our lives that needs to be held up by concrete. Something to consider. Please share your viewpoint
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