The Emergence of Complexity
Pleasing to the eye, the graceful arc of the bridge across the river Severn near the English village of Coalbrookdale in Shropshire has an elegant simplicity that conceals its revolutionary place in history. Constructed of five metal ribs, Iron Bridge (as it is known today) was the first complete bridge in the world to be made out of cast iron. When the bridge was opened to traffic on January 1, 1781, it marked the beginning of a new age in building infrastructure that would power the Industrial Revolution for the next 100 years.
Designed by Thomas Pritchard, the fabrication of the bridge involved over 1,700 individual components, each of which was individually cast and then fitted together. But the inherent complexity in this method was not fully recognized until repairs to the bridge were made in 1999/2000. A detailed, high-parity, computer-aided design (CAD) model of the bridge--created to help with the repairs--revealed small but significant variances in size between matching components. These variations indicated that a fundamental change had occurred in construction technique as a result of building the bridge.
As Bill Blake, a measured survey manager at English Heritage, observed: “The bridge shows a migration from joinery-driven fixing to engineering-driven techniques. No one had attempted anything like this before. We're surrounded by metal structures
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