Civil Engineering Reference
In-Depth Information
FIGURE 1.3
The Royal Albert Bridge built in 1859 over Tamar River at Saltash, England.
(Courtesy of Owen Dunn, June 2005.)
Brunel wrought iron railway bridge using large lenticular trusses (Figure 1.3). Other
important railway bridges built by Brunel on the Great Western Railway were the
Wharnecliffe Viaduct, Maidenhead, and Box Tunnel bridges.
Table 1.3
lists some
notable wrought iron truss railway bridges constructed between 1845 and 1877.
TheEnglishengineerWilliamFairbairnconstructedatubularwroughtironthrough
girder bridge on the Blackburn and Bolton Railway in 1846. Later, in partnership with
Fairbairn, Robert Stephenson designed and built the innovative and famous wrought
iron tubular railway bridges for the London-Chester-Holyhead Railroad at Conway
in 1848 and at Menai Straits (the Britannia Bridge) in 1849. The Conway Bridge
is a simple tubular girder span of 412 ft and the Britannia Bridge consists of four
continuous tubular girder spans of 230, 460, 460, and 230 ft (
Figure 1.4)
.
Spans of up
to 460 ft were mandated for navigation purposes, making this the largest wrought iron
bridge constructed. It was also one of the first uses of continuity to reduce dead load
bending moments in a bridge. Arch bridges were also proposed by Stephenson
∗
and
Brunel.
†
However, arch bridges were rejected due to concerns about interference with
navigation and the wrought iron tubular girder spans were built in order to obtain the
stiffness required for wind and train loadings. The construction of the Conway and
Britannia tubular iron plate girder bridges also provided the opportunity for further
investigations into issues of plate stability, riveted joint construction, lateral wind
∗
Stephensonhadstudiedtheoperatingissuesassociatedwithsomesuspensionrailwaybridges,notablythe
railway suspension bridge built atTees in 1830, and decided that suspension bridges were not appropriate
for railway loadings. He proposed an arch bridge.
†
In order to avoid the use of falsework in the channel, Brunel outlined the first use of the cantilever
construction method in conjunction with his proposal for a railway arch bridge across Menai Straits.
