This note describes the monitoring implemented during the ElevArch trial at Moco Farm in 2016. The monitoring had three components:
1. Before and after load tests.
2. Continuous monitoring of span change throughout the construction sequence.
3. More intensive monitoring during jacking operations, with a “dashboard” style display.
This month I had the double pleasure of 3 days in Bath which gave me time to have a good look at Pultney Bridge. It is a rather more elegant thing than most bridges I deal with, designed by Robert Adam. At first glance, and to be honest, over many “glances” for me, it looks like an elegant piece of Palladian symmetry. In fact, a close look reveals it to be far from symmetrical. The domed pavilions at the two ends are different and very differently placed.
So what is special about Twemlow? The first thing to note is the stable it comes from. Same line, same engineer as the famous Stockport viaduct but with the advantage, from our point of view, that it is a bit lower (so accessible) and hasn’t been widened. You will find it just outside Crewe. As you can see, it is substantial.
As many of you know I have been working with some precasters in New Zealand on developing modern arch bridges for the market there. One issue that is always raised is earthquakes. Usually on
the lines of “we can’t build those, they will just rattle down in a ‘quake.” Well they don’t. There are good reasons why they don’t. I knew there were a few arches in Christchurch, but the only way to find out how they fared in 2009 is to go and look and back in
November I finally got the chance.
The Old Bridge at Stirling is a wonderful thing. Only well through the 19thC was there a bridge over the Forth downstream of here. I had a collection of photos taken some years ago but they were slides and lost in a “library” of same so the opportunity to visit in July was very welcome. It is variously dated to 15thC or 16thC, though there were a number of timber predecessors including the one where Wm Wallace beat Edward 1st in 1297.
I have long wanted to visit this, though I knew far too little about it. A conference of bridge historians gave me an opportunity, and what an opportunity! This magnificent bridge, even from a distance, needs a modern camera with sweep panorama capability to capture most of it. There are several more spans to the right hidden over land these days. The river is, of course, the Vltava, immortalised by Smetena as Ma Vlast.
This bridge in Kirby Lonsdale is magnificent. The main spans around 17m and about a third of a circle. I didn’t get chance to measure but that is perhaps a 32ft or 32ft6 radius. A prominent feature is the break in the parapets which looks almost like the sort of lip you get in Google earth stitched pictures.
The railway South West of Exeter has some fascinating structures. Much of it was originally built single track, Broad Gauge, and with “Atmospheric” propulsion. Most of the viaducts were built with
stone piers and timber trusses, though the latter were more like cantilevers and suspended spans. It was always intended that those should be replaced as they became unserviceable. When that came
to, the track was doubled and a new alignment made so the new viaducts could be built along-side the old. At Bittaford, things got yet more complex as we shall see.
I have been wanting to get some decent pictures of William Edward’s bridge in Pontipridd for some time (years). March provided an opportunity but it was cold and wet and the pictures weren’t that good so try again. What I did find, though, was this amazing effort from IKB. Can it be chance that it is the same span?
Well, here is a blast from my past. I was reminded of this by a chance encounter earlier in the week. I went back specially in 2013 to get the photographs then never used them. There was a line, now
long gone, from Arbroath to Friokheim in Angus and the bridges were rather special. The bigger ones have been removed but this is left in place, despite the severe angles in the highway. And when I
look more closely, this is actually north of Friokheim over the old main line from Perth to Aberdeen, so maybe there are more somewhere.
Back to Natland to embark on a major review of Cumbrian damaged
bridges following the flood in late in December. The scale of that issue is visible from the map we built based on the data made public by Cumbria CC. Anyway, we visited Meg again in Natland so I
walked down to have a look at the little bridge there. Not high on the list of priorities but it tells us a lot about the flooding.
Having returned to Cheltenham, the scene of last month's bridge, I wondered whether there would be another similar bridge on the line. Google Earth doesn’t help a lot because street-view doesn’t extend to cycle tracks and disused railways. However, the next bridge East at Malvern Road proved to be very interesting. It is also a flying arch but is skew and has been widened with two concrete rib arches.
The role of serendipity in finding strange bridges is really quite outstanding. Last week I had to attend a meeting in Telford but arranged to meet various people on the way. I changed trains in
Cheltenham and had an hour to spare so wandered across the road for a coffee. I was reminded of the fact that there is a cycleway on a disused branch and noticed a bridge over it so let’s have a look.
The railway in Bath is interestingly routed. Obviously Brunel wanted his station in the city itself but there was no way in or out so he carried it along the opposite bank and crossed the river Avon with
two skew bridges to plant it just on the very corner. The viaducts
approaching the river on the two sides are remarkably different.
