Bridges presentation
lengths throughout the world. Steel arches and cantilevers were favoured for long spans because
they better withstood the impact, vibration, and concentrated loads of heavy rail traffic.
The earliest known use of steel in bridge construction was the 334ft (102m) suspension span across
the Danube Canal (1828) near Vienna (Austria), designed by Ignaz von Mitis. The steel eye-bar
chains were forged from decarburized iron from Styria. Steel halved the weight of wrought iron, but
remained prohibitively expensive for another forty years before steelmaking processes such as the
Bessemer and the open-hearth were perfected (it is uncertain whether the Styrian ironmasters
created real steel or whether the decarburization was a mechanical process resulting in a surface-
hardened steel, a kind of wrought iron rather than the mass steel that results from the Bessemer
process). The first major bridge utilizing true steel was the Eads Bridge (1874), the most graceful of
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