An Aside

This has absolutely nothing to do with the subject matter of this blog, but I hope might be of interest to at least some of my readers.

Today we were crossing a relatively modern (1960's or 70's I think, but modern by Durham standards) concrete footbridge across the River Wear, near to the University Student Union.  At the halfway point I spotted a very interesting mechanism for handling the expansion gap between the two halves of the bridge :

 

This appears to be a cast bronze C section let into the left hand side of the parapet, a T section on the right hand side, and a pair of hollow cylindrical rollers between the two.  I can't believe that this really is an active part of the engineering of the bridge, as it supposes that the two halves are somehow self supporting and do not rely on any strength from meeting in the middle.  Unfortunately it was not possible to view under the deck of the bridge to see what else there was between the halves.

I would like to think this is 1960's civil engineering in the raw, but I suspect it is just artistic detailing for show.  Nice to see though.

Postscript

Looks like I was right after all.  Since I wrote this post yesterday I have done some research.  This is the famous Durham Kingsgate bridge built by the University in 1963 and designed by Ove Arup of Sydney Harbour Bridge fame.  See this wikipedia article.  The two halves are self supporting and were each built parallel to the river, then rotated through 90° to make the crossing. Single use bearings were installed at the base of the supports to facilitate this.

I am so pleased with myself that I spotted this little detail with no prior knowledge.