Wednesday, October 19

Birthplace of the Industrial Revolution

More than thirty years ago I completed a school project on bridges. I recall being fascinated by the different construction methods used to span all manner of obstacles. I think this was moment that my love for civil engineering was born.  Today, I’m still fascinated by these remarkable feats of engineering; as more than one post in this blog will testify. Over the years, one bridge in particular has always captured my imagination; the Iron Bridge spanning the River Severn near Telford, England. Eveb the village it links is fondly called Ironbridge. Last weekend, while based in London for work, I hired a car and drove north to finally see the bridge for myself.

This structure is the world’s first cast iron bridge; possibly the world’s first large scale bridge span built entirely from metal. Upon completion in 1779 it heralded the arrival of an entirely new, significantly stronger, building material; one the ultimately built the modern age. Previously, only wood and stone had been available for large-scale construction. Within decades, other pioneering iron milestones including steamships, skyscrapers and large-scale industrial factories were emerging across the industrialised world.

All these milestones can be traced directly back to the actions of one man, Abraham Darby. In 1709 he first smelted iron using coke instead of wood-based charcoal. Coke, prepared from coal, was more plentiful than wood, thus enabling iron to be manufactured cheaply, in unprecedented volume. He lived in Coalbrookdale, a village located in valley less than a mile from the site of the Iron Bridge. The company he founded later went on to smelt iron for the first Iron Bridge, then built first steam locomotive for Richard Trevithick in 1803.

 Darby’s original iron furnace has been carefully preserved as part of the town’s fascinating Museum of Iron. The brick structure is largely intact despite centuries of weathering and neglect. Today, its crumbling remains are protected by a stunning triangular glass atrium. Exploring this structure was a surreal experience. As I looked into its bulbous interior I struggled to comprehend that one of the Industrial Revolution’s defining moments happened right here.

I feel a similar sense of awe and pioneering majesty standing under the iron lattice of the Iron Bridge. It’s a remarkably elegant and graceful structure as its design and construction was based on established carpentry techniques. This meant that each member of its frame was cast separately, and fastened using mortise and tenon, and dovetail joints. The bridge comprises more than 800 iron castings of 12 basic types, many of which were carefully customised to fit the final structure.

Its main arch span stretches 30.5 metres across the River Severn. At its highest point, the span provides 18 metres of clearance below. Smaller stone arches link the main span to the opposing river banks. When first completed, a toll was charged for its use. The original toll house still stands today on the edge of its southern approach. Vehicular traffic was barred from bridge in 1934, but it remains in use for pedestrians. Interestingly, a toll was still charged for pedestrians up until 1950. Today, you can cross the bridge for free, as well as wander scenic paths laid alongside and underneath it span.

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