Structural Design for Architecture
Fig. 1.23 Forth Railway
Bridge, Scotland, 1882-90,
Henry Fowler and Benjamin
Baker, engineers. The railway
track is carried on an internal
viaduct which is supported at
the junctions of the triangu-
lated main structure. [Photo:
A. Macdonald]
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across the entire span). This shows that the
intensity of internal force is at its highest at
the locations of the support towers and falls to
zero at the mid-span points, where the
adjacent cantilevers are joined. The distribu-
tion of internal force was modified by the
insertion of two hinge-type connections
between each set of cantilevers (Fig. 1.22c)
which had the effect of reducing the magnitude
of the maximum internal force at each support
tower.
Figure 1.22c represents, in diagrammatic
form, the basic configuration which was finally
adopted for the bridge. It was modified to give
improved load-carrying efficiency by matching
the longitudinal profile of the structure to the
pattern of internal forces so that the structural
material was concentrated at the locations of
highest internal force. It was further improved
by the adoption of a triangulated internal
geometry. Yet another decision taken by the
designers was to carry the railtrack on a
