Tuesday, March 2, 2010

Great Britain: Victoria Bridge (2)

Another view of the Victoria Bridge in Bath. The Happy Pontist pointed out that this bridge was designed by James Dredge, a local brewer who had some interesting ideas about structural mechanics. He patented his 'taper principle' that took into account that the load in the suspension chain was smallest at midspan and largest at the towers. He made use of this idea on the Victoria Bridge by designing a suspension chain with 12 links at the ends and only 5 links at mid-span.

He designed 50 bridges, but only the Victoria Bridge and the Stowell Park Bridge remain. In fact, the Victoria Bridge is sometimes damaged by vandals because it is in a secluded area. Work was recently completed to make the site part of a parkway that is more frequented by people in the hope that this will protect the bridge.

It is hard to imagine that Victoria Bridge ever carried much traffic. For one thing, the opening in the tower is only large enough to admit a single vehicle. R.A. Griffith's analysis shows that the current pedestrian load is about half the original vehicular load for this bridge.  Griffith also mentioned that Dredge may have gone into the bridge business so he could transport his beer into neighboring communities. However, another Dredge Bridge, the Ballievy Bridge in Ireland, was destroyed when a 27 ton lorry drove onto it in 1988, suggesting that these bridges were not designed for heavy loads.

Victoria Bridge has a span length of 45.7 m (150 ft), a deck width of 5.8 m (19 ft), a tower height of 6.4 m (21 ft), and a chain sag of 6.6 m (22 ft). We'll take a last look at this interesting bridge tomorrow.
Creative Commons License
Great Britain: Victoria Bridge (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

1 comment:

  1. There's another Dredge survivor at Bridge of Oich (quite well looked after), and a paper by McQuillan published in 1994 documented several other survivors in Northern Ireland and Wales (you can find the paper online but you have to pay).

    The original book explaining Dredge's ideas can be found on books.google.com.