The Forth road bridge

[Paul TParticipant @pault84577]

DOH!

Yes rouge is a red pigment applied to ladies faces and a common colour of stout gentlemen when climbing stairs, as can be seen in this prime specimen.

 La mer est transformée en peinture!" Not quite a painted sea?

It should have been written as Rogue: the Rogue definition is, a dishonest, knavish person; scoundrel. villain, trickster, swindler, cheat, mountebank, quack. The head and shoulders photos of such people often appear on crimewatch.

Paul

I hasten to add that the photo of DM as shown above has never been shown in any rogues gallery, but I cant account for any rouge galleries that might exist

 

Edited By Paul T on 11/12/2015 12:59:57

[Colin BishopModerator @colinbishop34627]

It's the defiant Chinese that I noticed….

Colin

[Paul TParticipant @pault84577]

Hi Colin

Well the Chinese are very definitely defiant but my brain is on some kind of miss-spell check…..I am so embrassed off with myself.

At least I caught my 'exercises in fruitility' mistake.

Paul

[Dodgy Geezer 1Participant @dodgygeezer1]

Posted by Paul T on 11/12/2015 11:49:25:

…………….

The Tay Bridge was lost during a storm but the collapse happened so quickly and involved such a large amount of the structure that engineers believe that a rouge wave was responsible.

Paul

Edited By Paul T on 11/12/2015 11:53:27

I've never heard that? My understanding was that the design was susceptible to failure of the ties, poor manufacture accentuated this, and worse maintenance left the bridge in a state where hight wind loading combined with a train's weight brought it down.

There is an alternative theory that the train derailed and hit part of the bridge. But the High Girders (which failed) were over 80 ft high, which would be a very large wave for an estuary, and surely noticeable elsewhere on the river bank…

[Paul TParticipant @pault84577]

Hi Dodgy

Thank you for getting involved.

The following is my understanding of the event and its causes but in true Ashley style I am adding the usual disclaimers that this is just my personal opinion and does not reflect the thoughts of the management no budgies were hurt during the writing of this post.

At the time the members of the investigating committee couldn't reach an agreement about the actual direct cause of the collapse.

Whilst it is true to say that poor workmanship and inferior iron were involved in the construction it is also recorded that the bridge had withstood a couple of similar storms whilst carrying heavier trains without incident.

It is very likely that excessive wind load in conjunction with another un-quantified force brought the structure down but it was considered unlikely that a derailed train moving at slow speed would have been a direct contributor to the collapse

Over the past 50 years there have been a few forensic re-investigations into the cause of the collapse and one of these explored the effect that a point load of a high wave would have on the lower parts of the structure and postulated that a high rogue wave could have impacted the supporting iron work and effectively pulled the legs out from under the rail deck.

This investigation showed that a combination of storm, train and defective build could not have brought the bridge down but when an extra force is applied, such as a wave, then the structure would suffer catastrophic failure in the load bearing columns directly below the train.

Its only a theory but it made interesting reading when I was younger. Of course there is alternative theory that it was sabotage or even impact by a UFO.

Ultimately we will never really know the cause of those 75 deaths.

Paul

[Dodgy Geezer 1Participant @dodgygeezer1]

Posted by Paul T on 11/12/2015 17:18:44:

…..

Whilst it is true to say that poor workmanship and inferior iron were involved in the construction it is also recorded that the bridge had withstood a couple of similar storms whilst carrying heavier trains without incident.

It is very likely that excessive wind load in conjunction with another un-quantified force brought the structure down but it was considered unlikely that a derailed train moving at slow speed would have been a direct contributor to the collapse

Over the past 50 years there have been a few forensic re-investigations into the cause of the collapse and one of these explored the effect that a point load of a high wave would have on the lower parts of the structure and postulated that a high rogue wave could have impacted the supporting iron work and effectively pulled the legs out from under the rail deck.

This investigation showed that a combination of storm, train and defective build could not have brought the bridge down but when an extra force is applied, such as a wave, then the structure would suffer catastrophic failure in the load bearing columns directly below the train.

….

This page went up about 9 years ago:

**LINK**

It references a computer analysis indicating that the gust wind loading during the storm alone was sufficient to break the central ties, leaving the bridge in an unstable state and prone to collapse when the next train passed over it.

Though it covers a lot of detail of competing theories, It does not mention a wave. Single intermittent 'Rogue Waves' are possible in the deep ocean, but in a shallow estuary such a wave would need to be propagating, and hence one might expect evidence of it. Have you any internet references to the wave theory?

[Bob Abell 2Participant @bobabell2]

Do we know what format the replacement Forth road bridge will take?

I assume it will be the type where all the cables terminate at the carriageway side walls and are fully accessible, similar to the one at Connors Quay?

Paul……What Safety Factor do they use on bridges?

Bob

[Tony HadleyParticipant @tonyhadley]

Bob,

Here is a link to the replacement road bridge, the Queensferry crossing. It looks to be a similar type to the one being built in our region at Runcorn across the Mersey, to help ease the traffic across the existing Runcorn bridge.

Years ago, I can remember having to cross the Forth bridge when working in Scotland, it was closed on a number of occasions not due to engineering problems then, but weather related fog issues. I take a diversion further along and use the Kincardine bridge, which is the diversion the traffic is currently using.

**LINK**

**LINK**

[Bob Abell 2Participant @bobabell2]

Thank you Tony…….Very interesting developments going on

I`m surprised they don`t modify the existing structure, using the same principal?…..Before it falls down!

The columns should be strong enough and the road anchorages are existing too

Probably impracticable for lots of reasons

Bob

[Paul TParticipant @pault84577]

Hi Dodgy

The wave reference goes back to the early 1980s and was part of a lecture on catastrophic failure. As I said it is just a theory and as such it can be accepted or ignored.

It is very possible that a modern computer simulation would provide a far more accurate solution.

Bob

Factor of safety is a question with a very wide scope for an answer, have a look at this Wikipedia page **LINK** it might not be 100% accurate but its easy to follow.

If the bridge has significant concrete and corrosion problems then the main columns and anchorage points will have the same problems.

But remember that this structure is a 'one off' and the only people who can really answer these questions are the engineers who are actually involved. My comments are nothing more than educated opinions and shouldn't be taken as hard fact.

Paul

[Tony HadleyParticipant @tonyhadley]

The bridge has now re-opened to traffic, excluding HGV's.

**LINK**

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