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GWR Route: Banbury to Wolverhampton
Olton Station: gwro2692
Drawing showing strengthening to be carried out on Brunel's
wrought iron bowed balloon-top bridge at Olton. The plan at the top of the
drawing shows the skew required to cross the Turnpike Road. The use of the
bowed balloon-top (tubular section) instead of a transverse flat flange was a
characteristic of Brunel's bridges and although it increased the theoretical
design strength and was more visually pleasing, it also increased the
construction complexity (and consequently cost) and could suffer from
undetectable internal corrosion (see 'gwro2694' for
a photograph of a section through a typical wrought iron balloon-top). The main
causes of replacement were however the gradual increase in locomotive axle
weights and the requirement to widen bridges over roads. The bridge at Olton
was eventually replaced with a lattice steel truss girder bridge when the
Birmingham Main Line was quadrupled in the early 1930s. National Archives TNA
(PRO) RAIL39/10/(14)
Robert Ferris
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