Showing posts with label Bath UK River Avon. Show all posts
Showing posts with label Bath UK River Avon. Show all posts

Tuesday, March 2, 2010

Great Britain: Victoria Bridge (3)

A photo of my wife and son standing in front of Victoria Bridge. The designer, James Dredge never became an influential bridge engineer, despite his innovative bridge designs.

Victoria Bridge (in Dredge's hometown of Bath) was his first bridge. He was a shareholder in the company that built it and they charged a toll of half a penny to cross it. The bridge weathered a powerful storm while it was being built which gave people confidence in it. It cost 1760 Pounds (in 1836) to build, it was turned into a public bridge in 1929, it was converted to a footbridge in 1946, and it's still in use.
The drawing above (from D. McQuillan's paper, From brewer to bridge builder: reflections on the life and work of James Dredge) shows one advantage of Dredge's 'Taper Principle.' A regular suspension bridge (on top) would collapse if you cut the cable in two but the Dredge bridge (at bottom) would remain supported if the suspension chain was cut in half.

I wonder if a modern steel suspension bridge was ever built using Dredge's 'Taper Principle?'


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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.
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Great Britain: Victoria Bridge (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.