Black Bridge, Nuneham: southern abutment failure

[whole diary]

[stuving]

... this type of bridge where the load is transferred at the corners of each deck. 

... and in the middle of the ends, made more complicated by the skew and the resulting stagger between the two sides.

[paul7575]

... this type of bridge where the load is transferred at the corners of each deck. 

... and in the middle of the ends, made more complicated by the skew and the resulting stagger between the two sides.

Did you notice at all that in some of the later photographs, eg #193, the centre main girder seems to be slightly lower than the sides? That is, the cross beams appear to pass over its bottom plate?  I originally thought the three bow string arches would be roughly the same size, but logically the centre one would need to be significantly stronger I suppose, like the keel of a ship.

[Mark A]

Screengrab from Network Rail's friday video.

Network Rail will have close up and quality photos to record the state of this part of the structure.



The screengrab deserves to be captioned in a way that credits a certain station between Cardiff and Port Talbot, but given its continued newsworthiness I'm still referring to this as the 'Paul Clifton Suspension Bridge'.

Mark

[ellendune]

... this type of bridge where the load is transferred at the corners of each deck. 

... and in the middle of the ends, made more complicated by the skew and the resulting stagger between the two sides.

Good point.  I had assumed from some of the historical descriptions that each track had a separate bridge deck. I was wrong. Also I had not appreciated that there was a skew. Interesting that the central beam appears to project further back into the the abutment than either of the side beams.

I suspect someone has now made careful measurements of the ends of the trusses and will be designing fabricating some new steelwork to attache the new bridge bearings.   

[Mark A]

Is it the case that this aspect of the steel spans at Nuneham is rather peculiar and possibly uncommon?

Mark

[stuving]

Is it the case that this aspect of the steel spans at Nuneham is rather peculiar and possibly uncommon?

Mark

I doubt it. Nobody laid out a railway line with turns so as to line up exactly at right angles to every road or river! I suspect most bridges are skew, though some shorter ones have their abutments turned to be true to the bridge.

Interesting that the central beam appears to project further back into the the abutment than either of the side beams.

If you draw a line between the ends of the two side beams that's true. I think the centre beam is longer than the side beams, so that each half deck ends at right angles to the bridge axis. You can see this, just about, in other parts of the video. How else would you do it?

[Electric train]

Is it the case that this aspect of the steel spans at Nuneham is rather peculiar and possibly uncommon?

Mark

Look at the 2 road over rail bridges on the approach to Paddington very large skew bowstring bridges about the same vintage as Nuneham

[ellendune]

Interesting that the central beam appears to project further back into the the abutment than either of the side beams.

If you draw a line between the ends of the two side beams that's true. I think the centre beam is longer than the side beams, so that each half deck ends at right angles to the bridge axis. You can see this, just about, in other parts of the video. How else would you do it?

Ah that makes sense, though not obvious from the screen grab.  I must look at the whole video again.

[paul7575]

A chap called Brian Daniels has taken a good sequence of photos yesterday, with the piling rig in action, they can be found on his Flickr photo stream here:

https://flic.kr/p/2oAGjij

It’s possible to get an idea how close to the end of the span the piles are being installed.  There’s a good shot showing the mid-stream pier, but unfortunately there’s no details of any of the span centre bearings or securing points, must be hidden by masonry?

Paul

[Mark A]

Thanks for that link, those are crisp photos.

Indeed, no indication that the bridge is carried on more than rudimentary fixed steel bearers at the centre pier and ditto, perhaps originally sliding, at the land abutments. This is the sort of bearing used at the likes of Finmere's long out-of-use rail over road bridge. The Finmere example nmaintained since whenever and thoroughly seized, those had worked their masonry bearers loose and generally caused mischief. Whether those at Nuneham, to add to the merriment, were able to wiggle that abutment like a loose tooth is another matter.

Another of those photos is a good portrayal of the structure's deck as set on the centre pier being deliberately canted, as the line, crossing the river, is on a curve.

Mark

[CyclingSid]

Not sure if these are from the same source:
https://twitter.com/sonic_speedbird/status/1658464574428028929?cxt=HHwWgoDR9cqvhoQuAAAA
via Paul Clifton

[paul7575]

Images from Network Rail on Twitter show the progress with the row of piles, they basically line up with the ends of the three main girders, it looks like a small area of deck plating has been removed for vertical access:

https://twitter.com/networkrailwest/status/1658843943038009349

I’m surprised they’re saying it’s just starting today 17th, given the previous photos taken on the 15th…

Paul

[Electric train]

Images from Network Rail on Twitter show the progress with the row of piles, they basically line up with the ends of the three main girders, it looks like a small area of deck plating has been removed for vertical access:

https://twitter.com/networkrailwest/status/1658843943038009349

I’m surprised they’re saying it’s just starting today 17th, given the previous photos taken on the 15th…

Paul

Is there a difference between foundation piles ie those to support the bridge which may have been augered and filled with reinforced concrete and the abutment piles used to retain the backfill which may be pile driven cam sheets ie "hammered in" ??

[stuving]

Images from Network Rail on Twitter show the progress with the row of piles, they basically line up with the ends of the three main girders, it looks like a small area of deck plating has been removed for vertical access:

Exploiting the super-zoom facility of Flickr, you can see what they have done in one of yesterday's pictures. There are two longitudinal members under the deck on each side, resting on the crossbeams. Because of the skew (very clear in today's overhead view) they extend varying amounts beyond the last crossbeam. These stringers are made of short pieces joined by riveted plates, and it looks as if the end piece has been unriveted in each case. While it's hard to see, I think the end crossbeam meets the western (far) side girder right at its end, so part of this must have been unriveted as well. (Yes - that's visible in one of today's pictures.)

[Electric train]

Images from Network Rail on Twitter show the progress with the row of piles, they basically line up with the ends of the three main girders, it looks like a small area of deck plating has been removed for vertical access:

Exploiting the super-zoom facility of Flickr, you can see what they have done in one of yesterday's pictures. There are two longitudinal members under the deck on each side, resting on the crossbeams. Because of the skew (very clear in today's overhead view) they extend varying amounts beyond the last crossbeam. These stringers are made of short pieces joined by riveted plates, and it looks as if the end piece has been unriveted in each case. While it's hard to see, I think the end crossbeam meets the western (far) side girder right at its end, so part of this must have been unriveted as well. (Yes - that's visible in one of today's pictures.)

New parts, stringers, cross members may be being fabricated to match the new bearings,