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GWR Route: Banbury to Wolverhampton
Olton Station: gwro2694
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Although not of a Warwickshire bridge, this photograph
provides a useful illustration of typical construction details involved in
Brunel's wrought iron balloontop plate girder bridge beams. The section
through the tubular flange was cut during this bridge's replacement in 1953 -
the bridge having been originally built over one hundred years previously in
1848. The vertical iron plate would only have been within the tubular flange at
the bridge ends, where the balloon-top curved down. The plate girder has
vertical web stiffeners at regular intervals and the riveted joints in the
balloon-top are butt-type with a curved cover plate or butt-strap. Normally
there would be a second butt-strap on the other side of the main plates being
jointed (in this case inside the tubular flange) and both these butt-straps
would be 75% of the thickness of the main plate. This made a stronger joint
than a lap joint arrangement, due to the equal forces produced by the double
shear on each rivet.
Robert Ferris
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