OT: What do you think of this bridge?

[Tim Downie]

I've posted to a couple of engineering groups but I reckon there's enough talent here to answer my question. ;-)

There is a local footbridge which causes me some concern whenever I see it. I'm not an engineer but it looks unsound to me. Here are 4 photographs I took this morning.

first two show the flattening of the first arch and the second two show cracks in the stonework on the bridge above the apex of the flattened arch. The third shows a 2 -3mm crack in the stonework on the upstream side and the fourth shows a longer (but narrower) crack on the downstream side.

Should I be chasing up the local council about it? That it's not "right" is obvious. What I'd like to know is if it's dangerously wrong.

Tim

[Andrew Gabriel]

If the bridge is just a conventional arch structure with nothing else contributing to its strength, then it looks horribly unstable to me. The arch will not dissipate very much load over the flattened area safely IMHO. There may come a time when it won't even sustain it's own weight, but I certainly wouldn't want to jump up and down at that point now! It looks like the left hand pier has sunk and possibly been pushed out a little by the force around the arch. Assuming the handrail was a stright line originally, that looks like a sinkage equal to nearly three courses of stonework in height (I can't see clearly on the old laptop I'm using at the moment).

Any idea how long it's been like this and how fast it's moving? Are there any older photos of it you can compare against?

However, I would say you should contact the council as a matter of some urgency.

[john]

its ultimate working load. I would stay well clear, and warn off the old gent in a habit of crossing it.

[Colin Wilson]

I`m no architect (and I suck at DIY) but it looks rather 'ick to me - there`s no harm in contacting the council and / or your local councillors / MP to see if it can be checked out properly.

[Rob Morley]

It's a footbridge.

[Rob Morley]

The flattened section will have very little inherent strength, and is in danger of collapsing under its own weight at some point - when that point will be might be extrapolated from how long it has taken to get into this state. Are there no signs of remedial ironwork underneath the arch?

[Christian McArdle]

Indeed, which is probably why the 100+ tonne truck caused so much damage!

Christian.

[Markus Splenius]

You have a grid reference for this bridge so I can enter it into my GPS? The GPS can then bleep at me if I ever get close to remind me not to cross it! :-)

Markus

[Tim Downie]

So I'm not the only one. ;-)

Sorry, I can't really say. It's looked like this for as Long as we've lived here (13 years) but the cracks look pretty fresh, particularly the one you can see through.

Of course without knowing the timecourse of the movements it's hard to make any judgements but I would *hope* that the council are monitoring these cracks.

I'm sure there must be somewhere. It's the Auld Brig in Ayr but I haven't found any good photos on Google.

Any suggestions a to which would be the most appropriate dept?

Tim

[Tim Downie]

It's hard to get into a position to see but it doesn't look like it.

Tim

[Tim Downie]

That's it there.

[Sam Nelson]

I'm not sure of that. Stone arches are astonishingly resilient structures and take a great deal of punishment. Take the stone bridge at Mostar, for example. Stone structures are a lot more flexible than you might think. It looks, though, as if the pier might be sinking, slowly.

There's an old picture in an archive at Aberdeen Uni that tantalisingly misses that end. I know one or two people that have lived in and around Ayr for ages, though...

Roads, I should think. If anyone at your council offices gets anything done, it's usually the roads department. If the roads are crap, you can be pretty sure everything else will be crap as well.

[Sam]

To take the post even more off topic, though considering the date quite appropriately so, here's what Burns had to say about it.

'_ayr.htmSam

[Aidan]

There's usually a Dangerous Structures department, who are generally involved with wobbly walls, shaky scaffolding or sagging roofs. They will have access to structural consultants who will be able to give a reliable opinion. Send them a copy of the pictures and a letter detailing the defects you've noticed. Send a copy by recorded delivery and keep a copy if you're really concerned. Is that the bridge of Tam O'Shanter fame? When's Burns night? Oh, I see that it's tonight.

This is a Scottish joke, isn't it?

[Aidan]

Sam wrote; here's what Burns had to say about it.

'_ayr.htmWell, that's different. We're all agreed on immediate demolition then? And can someone translate that?

[The Natural Philosopher]

I'd say it probably is. Or if not yet, soon will be.

I and others repored a fra less seriosu distirtin in a railway bridge many years ago. It was closed for months while tey fixed it.

If it were down to me, I'd probably close that footbridge permanently, now.

And let others argue over the cost benefit of repairing it.

[andrewpreece]

The bridge appears to have four 'hinge-points', if the points where the arch butts onto its supports are included with the two hinge-points visible higher up the span. An arch can cope with three hinge-points with no effect, but get four and it's a prerequisite to collapse. That doesn't mean it will of course, as the strain may be taken up via other paths than the arch ring, but it's IMO a rather dubious structure to have open to the public. May I refer you to 'Structures' a paperback by J.E. Gordon, page 190, fig. 16, I believe it's still in print.

Andy.

[mike ring]

"Sam" wrote in news:41f67598$0$19164$ [e-mail]:

"Ascribed to Burns"!

That's a McGonagall if ever I read one.

mike

[mike ring]

The Natural Philosopher wrote in news: [e-mail]:

With your natural linguistic talent, could you translate the pome?

mike ;-)

[Mike]

From the look of it it's not far from the point of no return. Assuming that's a major river below I'd hate to think how they'd prop this up to repair it either.