[15] Bridges

The invention of the steam locomotive changed bridge building because stronger spans* were needed. Iron was first used for chain cables of a suspension bridge** over the Tees River, in England, in 1741. The flooring*** was laid directly upon the cables. Abraham Darby and John Wilkinson built the first iron bridge over the Severn River at Coalbrookdale, England, in 1779. This 100-foot (30-meter) arch bridge is still in service. Thomas Telford built the first modern iron arch bridge in 1813. It is Craig Ellachie Bridge over the Spey River, Scotland, with a 150-foot (46-meter) span. It was not built up of cast-iron blocks in imitation of masonry as were previous iron arch bridges but was the first to use an arch made up of iron trusses****. In 1819 – 1824 Telford built the forerunner of the modern suspension bridges – the 570-foot (174-meter) span over Menai Strait in Wales. It had wrought-iron***** chains for cables.

The first to design railroad bridges was George Stephenson, who with his son Robert invented the Rocket, the first practical locomotive. Robert Stephenson built the Britannia Tubular Bridge over Menai Strait in 1846. Its two boxlike tubes were made of iron plates riveted****** together. Many truss designs were patented in the 1850s for railroad bridges. After numerous failures of cast-iron bridges, wrought iron was used, then steel.

The first bridge to use steel extensively was the triple-arched Eads Bridge over the Mississippi at St. Louis, Mo., in 1874. It was an important link in the transcontinental railroad and made St. Louis a crossroads. This bridge was named after James B. Eads who designed it and was in charge of its construction. The modern era of steel arch building began in the 20th century. The Bayonne Bridge, completed in 1931 over Kill van Kull between New York and New Jersey, has a 1,652-foot (504-meter) span. Australia’s Sydney Harbor Bridge, finished in 1932, is only 2 feet (0.6 meter) shorter. At the turn of the 20th century, the construction of masonry arch bridges reached its peak. Then the more economical and easier to use concrete became common for arch bridges. Later, reinforced concrete******* and then prestressed concrete******** were used.

Notes: *span – пролёт моста

**suspension bridge – висячий мост

***flooring – настил

****truss – балка, ферма (моста)

*****wrought iron – кованое железо

******to rivet – приковывать

*******reinforced concrete – железобетон

********prestressed concrete – предварительно напряжённый бетон

To be read after Lesson 7