Talk:Tubular bridge

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Ancestor

The Ancestor box says that the box girder bridge in an ancestor of the the tubular birdge. But surely it's the other ways around. Stephenson's Britannic Bridge completed in 1850 is often called the world's first box girder bridge. Jooler 13:13, 8 May 2006 (UTC)[reply]

First span over 30-odd feet

The statement that In the case of the Britannia Bridge this technology allowed a bridge with spans up to 460-feet (140-m) long to be constructed, when until then the longest wrought iron span had been 31 ft 6 inches (version) needs qualification re the structural type of bridge to which it applies. --Una Smith (talk) 21:49, 30 March 2009 (UTC)[reply]

Agreed. The 31 ft 6 inch span reference must be the 1841 road bridge over the Pollock and Govan railroad by A. Thompson. This was this was the first wrought iron girder bridge. Significantly longer truss and arch bridges of iron were already in existence, although they were made of cast iron or a mixture of cast and wrought iron. The important thing is that the tubular design in wrought iron allowed a substantial increase in length for railway bridges. I'll rewite this bit. Meters (talk) 20:18, 4 April 2012 (UTC)[reply]

Much longer suspension bridges were already in use, using wrought iron chains. However, owing to their flexibility, suspension bridges can't be used for railways (later suspension bridges, possibly including Chepstow within this, became more rigid and did see use for railways). Andy Dingley (talk) 21:42, 4 April 2012 (UTC)[reply]

The first railway suspension bridge I am aware of was Samuel Brown's 1830 bridge over the Tees (281-foot span). It was far too flexible for railway use and piles had to be driven underneath the platform to support it. Even then it soon failed. John Roeblings's 825-foot span, 1855 Niagara Falls Suspension Bridge over the Niagara Gorge (between Canada and the US) is generally considered to be the world's first successful railway suspension bridge. Suspension bridges went on to become quite common in the US, long before in the UK. I don't know what you mean by your reference to the Chepstow bridge. Did you mean Brunel's 1852 Chepstow Railway Bridge? I don't consider that to be a suspension bridge. Meters (talk) 23:22, 4 April 2012 (UTC)[reply]