Forth Road Bridge - now in intensive care

[robin]

IBIS Budget Edinburgh Park. Stay over.

Steel you say? How about buying local. Save a few jobs. FFS.

Much as I appreciate the sentiment I don't think 20m of premium steel is going to save the British steel industry!

[robin]

Crazy idea perhaps, but could they not still allow foot passengers over? Park n ride car parks in fife, busses collect at Sth Queensferry?

Far from ideal, but it's an option to sitting in traffic for Kincardine Bridge, plus FRB-Ed centre roads won't be as busy because of the closure. Or utilise the trams, must be plenty alternatives there with some thought.

Still an utterly awful prospect for thousands regardless....

I think they've avoided it thus far because they don't want people to gawp. Once everyone is bored with the story, they will surely re-open to pedestrians as they cannot weigh enough to notice.

[campbell]

But is the closure because traffic might cause a failure...or because it might fail at any time?

If the latter, clearly they can't let anyone on it. Except Fifers *




* JOKE

[kenny]

Jesus, that's some serious material failure! Be interesting to see what caused it from an engineering perspective.

There is a good sketch of the "girders" of the bridge on the BBC site now; I believe this section of the decking is not suspended directly by the cables but rather sits on the "truss"; the traffic banging on the deck would compress the very thing that has fractured, not stretch it; but I know nothing of engineering and metallurgy.

Anyway, if you do think that the hanger should be under compression, but it has failed because of stretch then that tells you that the rest of the decking must be hanging off that truss (which it shouldn't be - it should be hanging off the cables, it's a suspension bridge). So I hope I am a foolish amateur and a bit of gaffer will fix it ... otherwise the bridge ain't ever opening again!

Cheers,
Robin

It's a tension member rather than compression. The last internal diagonal member will be carrying the bulk of the bottom chord truss load back to the support point of the tower by the looks of the diagram on the BBC. In theory the bottom chord past the last node point will have very little load in it, if the truss has been designed as a top chord hung support, which would make sense if the suspension cables were connected to the top of the truss at road level.

The Engineer on the BBC described it as a shear failure, looks more like brittle fracture, the bottom chord connection at that point appears to be a pin, so it wont be subject to a huge shear force.

[rossybee]

Crazy idea perhaps, but could they not still allow foot passengers over? Park n ride car parks in fife, busses collect at Sth Queensferry?

Far from ideal, but it's an option to sitting in traffic for Kincardine Bridge, plus FRB-Ed centre roads won't be as busy because of the closure. Or utilise the trams, must be plenty alternatives there with some thought.

Still an utterly awful prospect for thousands regardless....

I think they've avoided it thus far because they don't want people to gawp. Once everyone is bored with the story, they will surely re-open to pedestrians as they cannot weigh enough to notice.

I get the initial gawp-factor, but thinking more long-term....just a guess, 30-40mins to walk across? I've walked the Tay bridge and back plenty (can't stay in fife too long ) and would do wonders for folks' fitness and elf

[pete]

Radio tonight was suggesting it might, in the future, be limited to buses, cyclists and pedestrians.

Wasn't there a story a few years ago that it was going to fail and they had put off building the replacement for too long, such that the current bridge would expire before eh replacement was finished?

[campbell]

Wasn't there a story a few years ago that it was going to fail and they had put off building the replacement for too long, such that the current bridge would expire before eh replacement was finished?

Yes.

All the while, the iconic 125 yr old rail bridge stands proudly, and ever so slightly smugly, nearby. If you listen really carefully, you can sometimes even hear her smirking...

[Stevoraith]

If that's true then we're in serious trouble.

My next door neighbour is a manager for the concrete contractor on the new bridge and he says there's no way it'll be completed on schedule (summer '16) and it looks like it'll be closer to the end of the year.

If the Forth bridge is closed for that long there will be serious consequences.
I'd imagine more than a few people will lose jobs and livelihoods- it would certainly have serious financial implications for me.
Let's just hope they get it all sorted sooner rather than later.

[rossybee]

Can employers temporarily introduce flexi time during these times of disruption?

I know most would probably not want to but in the interests of maintaining good employees?

[Dark]

Radio tonight was suggesting it might, in the future, be limited to buses, cyclists and pedestrians.

Wasn't there a story a few years ago that it was going to fail and they had put off building the replacement for too long, such that the current bridge would expire before eh replacement was finished?

The plan has always been that the old bridge will be restricted to buses, cycles & pedestrians once the new bridge opens. Much of the road works on the south side are to construct a priority bus lane alongside the existing A90.

Main concern in the past were the wire strands in the suspension cables corroding & breaking. They have now installed a drying system and monitoring equipment and the number of wire breakages has declined significantly.

[robin]

It's a tension member rather than compression. The last internal diagonal member will be carrying the bulk of the bottom chord truss load back to the support point of the tower by the looks of the diagram on the BBC. In theory the bottom chord past the last node point will have very little load in it, if the truss has been designed as a top chord hung support, which would make sense if the suspension cables were connected to the top of the truss at road level.


The Engineer on the BBC described it as a shear failure, looks more like brittle fracture, the bottom chord connection at that point appears to be a pin, so it wont be subject to a huge shear force.

Agreed -I was wrong - it is in tension normally.

[kenny]

Can see the SNP declaring a state of National Emergency shortly.

tut

Have they found a way to blame the Tories yet?

[Scottish Scrutineer]

This gives a better sense of the scale of the problem. Early reports were that other members are also requiring attention.
I think it may not be long before we all get reminded what it was like to cross the Forth by ferry.


Sent from my iPhone using Tapatalk

[robin]

Can see the SNP declaring a state of National Emergency shortly.

tut

Have they found a way to blame the Tories yet?

The bridge was built under the conservatives ... does that help?

[j2 lot]

How has that gone unchecked for so long !!