Outline of Developments in Design Using Ferrous Metals
Prior to 1779, when the Iron Bridge at Coalbrookdale on the Severn was completed, the
most important materials used for load bearing structures were masonry and timber.
Ferrous materials were only used for fastenings, armaments and chains.
The earliest use of cast iron columns in factory buildings (circa 1780) enabled relatively
large span floors to be constructed. Due to a large number of disastrous fires around
1795, timber beams were replaced by cast iron with the floors carried on brick jack
arches between the beams. This mode of construction was pioneered by Strutt in an
effort to attain a fire proof construction technique.
Cast iron, however, is weak in tension and necessitates a tension flange larger than
the compression flange and consequently cast iron was used mainly for compression
members. Large span cast iron beams were impractical, and on occasions disastrous
as in the collapse of the Dee bridge designed by Robert Stephenson in 1874. The last
probable use of cast iron in bridge works was in the piers of the Tay bridge in 1879 when
the bridge collapsed in high winds due to poor design and unsatisfactory supervision
during construction.
In an effort to overcome the tensile weakness of cast iron, wrought iron was introduced
in 1784 by Henry Cort. Wrought iron enabled the Victorian engineers to produce
the following classic structures. Robert Stephenson’s Brittania Bridge was the first
box girder bridge and represented the first major collaboration between engineer,
fabricator (Fairburn) and scientist (Hodgkinson). I.K.
