The Design of Modern Steel Bridges - TEDI

Types and History of Steel Bridges 7
its deck had to be replaced in 1839, 1893 and again in 1939. Telford also built
the 327 ft (100 m) span suspension bridge at Conway for the same Holyhead
Road at about the same time. The success with these two suspension bridges
brought about a new era of long-span bridges.
Isambard Kingdom Brunel built Hungerford pedestrian suspension bridge
over the Thames at Charing Cross which, however, had to be removed 20 years
later to make room for the present railway bridge. William Clark built
Hammersmith Bridge, Norfolk Bridge at Shoreham, the bridge at Marlow over
the Thames and the 666 ft (203 m) span bridge over the Danube at Budapest –
all suspension bridges. Several other suspension bridges with wire cables were
built in Europe, the most remarkable being the Grand Pont at Fribourg,
Switzerland, by Chaley, which had a 800 ft (244 m) span supported by four
cables each of 1056 wires, 3 mm diameter. A competition was held for the
design of a bridge over the Avon Gorge at Clifton, Bristol. Brunel submitted a
design for a suspension bridge of 1160 ft (354 m) span. Telford was a judge for
the competition and did not consider such a long span practicable. In a second
competition in 1850, Brunel’s design of a 600 ft (183 m) span was accepted.
Work started but was abandoned due to the contractor going bankrupt. In 1860,
a year after Brunel’s death, work was resumed with some changes in the design
and completed in 1864; the chains of Brunel’s Hungerford bridge were reused
here – they had wrought iron shafts with eyes welded to their ends by hothammering.
This beautiful bridge is still carrying vehicles – a great testimony
to a very great engineer.
By the middle of the nineteenth century, good-quality wrought iron was
being produced commercially, replacing cast-iron for structural work and
being used extensively for shipbuilding. This material was ductile, malleable,
strong in tension and could be riveted. William Fairbairn had already designed
a riveting machine.
In the second half of the eighteenth century, the coal industry in England was
using steam engines for pumping out water, and wooden or iron rails for moving
coal wagons. In the first decade of the nineteenth century, several collieries
around Newcastle had steam boilers on wheels running on rails by means of
ratchet wheels for hauling coal wagons. In 1814 George Stephenson built an
engine which did not need any ratchets to run on iron rails. In 1825 Stephenson’s
Rocket engine ran on the Stockport-to-Darlington railway. This railway
was followed by Manchester–Liverpool and London–Birmingham railways.
Soon railways grew all over Britain, then in Europe and North America. This
produced an insatiable demand for bridges (and tunnels), but these bridges had
to be sturdy enough to carry not only the heavy weight of the locomotives, but
also their severe pounding on the rails. They also had to be built on a nearly
level grade; otherwise the locomotives could not pull the wagons up.
George Stephenson built two types of bridges for his railways – a simple
beam of cast-iron for short spans over roads and canals, and cast-iron arches
for longer spans. The most striking example of the latter type was the