St Johns, Woking, Footbridge Closure Dec23

[Deepgreen]

The problem is that if the deck comes in by rail, it has to be turned through 90° - and it's long. Not too hard to tandem lift with two crawlers, since they can move with a load on the hook, but I doubt if the Kirovs can.

No-one is going to use this discussion as the basis of a method statement Meanwhile I quite enjoy speculating - I used to do this sort of stuff for a living, and it's so much easier as a spectator!

Quite. I seriously wonder if a span in two halves is the best way, one crane takes each and then they are bolted together in situ. Would be better done in calm weather! Or a couple of Chinooks with a full span... Edit - I've also just looked more closely at the photo with the class 69, and it looks like there is an area of discolouration on the deck above the DFL, which could just be old graffiti or paint, etc., from an impact.

 

[Benjwri]

Just looking at the images with the 56 on the USL again, that brick foundation pier on the DSL (far) side (stanchion covered in ivy), although the brickwork is broken in a similar manner to that of the obviously recently damaged centre pier (in the 10 foot), the damage to the DSL side pier does not look recent, no signs of fresh brick rubble either in the crack or lying around. But obviously a point of weakness none the less.

The far side brick work looks recently fractured in the original image, the inside of it looks far lighter than the surrounding mortar. Likely less 'messy' because it fratured cleanly along the mortar and took less of the impact.

If it had been struck hard enough to fracture two brick piers wouldn’t that flimsy bridge have some very visible deck damage, particularly if it was a narrow hit such as a digger arm?

To me it looks like if something hit it it was only just too big, and it lifted the bridge over it, then dropped it back down. This will have put the supports in tension. Mortar without wear is assumed to have negligable tensile strength for structural purposes, and in reality is around 400x weaker than steel in tension. This makes it the obvious failure point, and it is probably because this failed that the steel itself did not fail. There is deformation in the bridge deck, which can be seen from images I posted with my origninal explanation of how this was likely to be subsidance.

 

[najaB]

Would be better done in calm weather! Or a couple of Chinooks with a full span.

Couple of these could be useful: https://en.wikipedia.org/wiki/Hybrid_Air_Vehicles_Airlander_10

 

[Benjwri]

Regarding the replacement, it will have to be a bespoke design most likely, and they'll bring it in by rail and use a rail-crane. It's a very similar situation to the Lanks Hill footbridge in Danescourt. At a guess it will end up being supported by the two outer peirs, and maybe a central one, but that will probably come down to the cost of building the middle pier again, vs the cost of the design and contruction complexities of bolting a span together on site. Photo of them lifting part of the section of the footbridge in below:

And more details on the Lanks Hill footbridge available here.

The new bridge will be installed by rail-crane that will be situated in the proximity of the bridge at track level. It will be delivered to the site by rail in 2 to 3 sections. Due to space restrictions at the site, the design needed to be able to be constructed elsewhere and put together on-site, limiting the impact on rail services through Danescourt, and minimising the need for longer-term rail closures and disruption to lineside neighbours.

 

[DelW]

When you say 'crawlers', do you mean vehicular from the side, and not from the railway itself?

I was referring to tandem lifting long spans with crawler-mounted cranes in general terms - not suggesting that crawler cranes would be at all feasible here.

Quite. I seriously wonder if a span in two halves is the best way, one crane takes each and then they are bolted together in situ.

Two halves would make transport easier too. With a temporary scaffold pier in the ten-foot, to support the joint, the same crane could do both spans, though that does need some possession work in advance and afterward, for the temporary pier.

 

[Deepgreen]

Just looking at the images with the 56 on the USL again, that brick foundation pier on the DSL (far) side (stanchion covered in ivy), although the brickwork is broken in a similar manner to that of the obviously recently damaged centre pier (in the 10 foot), the damage to the DSL side pier does not look recent, no signs of fresh brick rubble either in the crack or lying around. But obviously a point of weakness none the less.

I imagine the centre pier, being adjacent to the presumed impact, has suffered more direct damage, while the bridge deck's twisting has absorbed some energy, making the far abutment less violently affected, perhaps just creating a clean crack rather than a more explosive reaction. The result would be less/no revealing of interior brickwork as has happened on the centre pier.

 

[Meerkat]

How heavy are these fancy lightweight (composite?) footbridges - can a Kirov lift one up then it’s spun round and lowered onto two piled piers?
I can’t see the bridge needing more loading gauge than a 444 carriage (you do walk through them above platform height after all). The two bridges it would have to go through between Woking yard and the site are on pretty straight bits of track.
Getting a one piece bridge to Woking yard might be a fun early Sunday morning job, but they get rail machinery in there on standard low loaders. Could always lift it out of Morrisons car park if necessary!

 

[Peter Mugridge]

How heavy are these fancy lightweight (composite?) footbridges - can a Kirov lift one up then it’s spun round and lowered onto two piled piers?

The three biggest rail mounted Kirow cranes in the country are rated at 125 tonnes, but a lot depends on the jib extension - the further the jib is extended, the lower the safe lifting load. This means a lot would hinge upon what the required reach would be to get the bridge into place.

 

[WesternBiker]

This is about 1mile away from the landslip, I’m actually working on this project.

Landslip no5 in as many weeks

With apologies for quality, this was taken from a train on the up slow about 15 minutes ago. Some sharply angled scaffolding next to the upright supports.

 

[Big Jumby 74]

this was taken from a train on the down slow

Up slow me thinks.....still a strange one, the incident that is. All evidence points to something travelling right to left (as per your image), ie wrong line over Down Fast or Down Slow, but still no obvious (severe) damage to bridge deck girder, so presumably slow speed and raised jib (or whatever) may have made initial contact with the underside of bridge deck, pushing the entire structure momentarily in an upward and Eastward (towards top left in your image), thus breaking the weaker brickwork at ground level. Sure it'll all come out in the wash !

 

[Deepgreen]

Up slow me thinks.....still a strange one, the incident that is. All evidence points to something travelling right to left (as per your image), ie wrong line over Down Fast or Down Slow, but still no obvious (severe) damage to bridge deck girder, so presumably slow speed and raised jib (or whatever) may have made initial contact with the underside of bridge deck, pushing the entire structure momentarily in an upward and Eastward (towards top left in your image), thus breaking the weaker brickwork at ground level. Sure it'll all come out in the wash !

Yes, but it's hard to know which way trains are running there now! IF it was an engineering train engaged on the embankment it would have been pretty slow and may just have been unlucky to have struck an already-weakened structure (although perhaps a blessing in disguise to have revealed such weakness before it potentially showed itself suddenly and catastrophically).

 

[WesternBiker]

Up slow me thinks.....still a strange one, the incident that is. All evidence points to something travelling right to left (as per your image), ie wrong line over Down Fast or Down Slow, but still no obvious (severe) damage to bridge deck girder, so presumably slow speed and raised jib (or whatever) may have made initial contact with the underside of bridge deck, pushing the entire structure momentarily in an upward and Eastward (towards top left in your image), thus breaking the weaker brickwork at ground level. Sure it'll all come out in the wash !

Whoa! Yes, up slow!

(In fairness I have just moved out of London…!!)

 

[Benjwri]

Yes, but it's hard to know which way trains are running there now! IF it was an engineering train engaged on the embankment it would have been pretty slow and may just have been unlucky to have struck an already-weakened structure (although perhaps a blessing in disguise to have revealed such weakness before it potentially showed itself suddenly and catastrophically).

The structure will have been weakened, but also unlucky if it was 'lifted' as the damage suggests, as I mentioned in my previous post:

To me it looks like if something hit it it was only just too big, and it lifted the bridge over it, then dropped it back down. This will have put the supports in tension. Mortar without wear is assumed to have negligable tensile strength for structural purposes, and in reality is around 400x weaker than steel in tension. This makes it the obvious failure point, and it is probably because this failed that the steel itself did not fail. There is deformation in the bridge deck, which can be seen from images I posted with my origninal explanation of how this was likely to be subsidance.

This won't have been something the bridge was designed to withstand or it would normally have to, I wouldn't say the fact it failed means it was unsafe, even if it wouldn't be designed in the same way today.

 

[WesternBiker]

Up slow me thinks.....still a strange one, the incident that is. All evidence points to something travelling right to left (as per your image), ie wrong line over Down Fast or Down Slow, but still no obvious (severe) damage to bridge deck girder, so presumably slow speed and raised jib (or whatever) may have made initial contact with the underside of bridge deck, pushing the entire structure momentarily in an upward and Eastward (towards top left in your image), thus breaking the weaker brickwork at ground level. Sure it'll all come out in the wash !

Your explanation certainly makes sense of the visible damage. Some of the brickwork had been cleared from along the damaged course, this morning, but a pile of loose bricks was left at the western end of the base.

 

[jwhite9185]

For the past week or so, a number of services from Waterloo have been crossing over the tracks and using platforms 1 and 2 at Woking. Likewise, those heading to Waterloo look to be departing from platform 4 at Woking.

Wonder if this has anything to do with it?

 

[Snow1964]

The three biggest rail mounted Kirow cranes in the country are rated at 125 tonnes, but a lot depends on the jib extension - the further the jib is extended, the lower the safe lifting load. This means a lot would hinge upon what the required reach would be to get the bridge into place.

Some cranes allow ballast counterweights to be added to the back, which increases the weight possible for a distance from centre of crane

But looking at photos of the site it would be relatively easy to have the crane on one of the centre tracks, a new bridge on wagons on the other centre track alongside it, then crane jib is almost vertical, which would be well within crane limits. Once hoisted, just need someone to grab a dangling rope at end and swing it around 90 degrees to across the tracks (when I say dangling rope mean long one, you don't stand under suspended load).

Unless the end abutments are weak not usually worth redoing the middle pier. Cranes are much bigger than 120 years ago (or whatever the date when that section was quadrupled), so doing it in two halves just complicates it. Sometimes easier to make modern footbridge longer and fix it on concrete pads set further back on good ground if there is query about stability of existing bridge footings

 

[TEW]

For the past week or so, a number of services from Waterloo have been crossing over the tracks and using platforms 1 and 2 at Woking. Likewise, those heading to Waterloo look to be departing from platform 4 at Woking.

Wonder if this has anything to do with it?

Yes. When the single line working is in operation down services via Basingstoke have to use platform 2 and up services from Guildford have to use platform 4 or 5.

 

[Meerkat]

Some cranes allow ballast counterweights to be added to the back, which increases the weight possible for a distance from centre of crane

But looking at photos of the site it would be relatively easy to have the crane on one of the centre tracks, a new bridge on wagons on the other centre track alongside it, then crane jib is almost vertical, which would be well within crane limits. Once hoisted, just need someone to grab a dangling rope at end and swing it around 90 degrees to across the tracks (when I say dangling rope mean long one, you don't stand under suspended load).

Unless the end abutments are weak not usually worth redoing the middle pier. Cranes are much bigger than 120 years ago (or whatever the date when that section was quadrupled), so doing it in two halves just complicates it. Sometimes easier to make modern footbridge longer and fix it on concrete pads set further back on good ground if there is query about stability of existing bridge footings

Pretty sure making the footbridge longer would involve buying land, and might cause access issues on the northern end as it goes markedly downhill from the end of the bridge.
Can a rail based piling rig do piles for it or would they need to be much chunkier than electrification ones?

They have built scaffolding towers around the piers, presumably for access to separate the deck from the piers.
There was a big rail/road crane on the down fast. A Demag ac55 city if that means anything to you.
Three road axles and a serious telescoping boom - to my untrained eye it looked meaty enough to do the lifting on its own.
Trains are going by very slowly.

 

[Lucan]

What would be wrong with keeping the original bridge deck and maybe the steel central piers (if they were not damaged by the impact), with new concrete footings for the piers? That would be a much simpler and quicker job.

 

[Benjwri]

What would be wrong with keeping the original bridge deck and maybe the steel central piers (if they were not damaged by the impact), with new concrete footings for the piers? That would be a much simpler and quicker job.

The entire deck is now curved, from whatever caused the issue. The deflection will be beyond allowable limits, and therefore the bridge deck is unusable and has failed as well.

 

[WesternBiker]

A great photo from GrahamA on the SWML thread (copied below), showing the bridge removed on Sunday, is on the thread "Another landslip on the SWML"

View attachment 148191
The unsafe footbridge near the St Johns area of Woking has been removed today. All four running lines were closed earlier, presumably when the central section was being taken down.

 

[Sultan]

I wonder if that machine is similar to what possibly hit the bridge in the first place.

 

[Meerkat]

I wonder if that machine is similar to what possibly hit the bridge in the first place.

That crane was brought in to take the bridge away. The land slip work was a load of the usual four wheel road rail cranes. The one with the pile driving set up would be the suspected culprit from purely size considerations, but not sure that had turned up before The bridge was found to be wonky.

 

[GrahamA]

In the post eschede environment, would we expect a replacement structure (assuming the opportunity is not taken by Network Rail to attempt to fait-accompli a closure), to be a single span to remove the pier in the middle?

Spoke to one of the contractors on Sunday evening and he said that a single span bridge would be used because "they wouldn't be allowed to have a central pier these days" (or words to that effect). The gap between the up and down fast lines is pretty narrow here. He also said the bridge would need to span 32 metres.

The sides of the cutting are quite steep at this point - more so than at the nearby slip site.

 

[Deepgreen]

This thread has some cross-over with this one, from the single-span perspective: https://www.railforums.co.uk/threads/which-single-span-footbridge-crosses-the-most-tracks.259364/ .

 

[Sultan]

I saw this update on the village Facebook group. Haven’t found a proper network rail link (yet) but seems that plans for a replacement are in the pipeline.

 

[Sultan]

Nice to see that Network Rail are inviting people to attend a Zoom meeting on 12th March at 7pm to talk about the replacement footbridge.

Great that Network Rail has agreed to an online meeting on St John's Footbridge to set out their plans. The Zoom meeting will take place on Tuesday 12th... | By Cllr Ayesha Azad | Facebook

PM me for the Meeting ID / Passcode if you are unable to see them in the Facebook link above.

 

[Sultan]

I was unable to join the Zoom call (#57) this week. Did anyone else on the forum join Network Rails call about the replacement bridge? Any info greatly appreciated.

Thanks

 

[Benjwri]

I was unable to join the Zoom call (#57) this week. Did anyone else on the forum join Network Rails call about the replacement bridge? Any info greatly appreciated.

Thanks

A local county councillor made the following post:

Thank you to the 70 or so residents who joined the meeting with Network Rail last night about St John's Footbridge. While there was obvious frustration - particularly of those that live nearby the bridge and the land slippage - I hope that for the most part, people were pleased with the meeting and its explanations of the current situation.

Fabrication and construction of the earthworks and bridge isn't something that can be done instantly but I'm still focused on a 2024 delivery and will continue to hold feet to the fire over this. We've also managed to get a bigger and wider bridge for the crossing and something that allows views of the trains passing as well, which is great news. I agree with those who weren't completely convinced though that the perforated design achieves everything in this regard and I am doing further work on this.

The meeting was recorded - anyone who would like to see it can contact Network Rail on 03457 11 41 41 Quoting Wessex/Woking/St John's Footbridge or on [email protected] quoting the same.

I have to say that I have been impressed by the community relations efforts from NR compared to many that I see from private and regulated industry - the commitment to explore a local roadshow here in St John's and Hook Heath further down the line is very welcome indeed.

[photos below edited to protect identities for GDPR purposes, those visible are Network Rail employees]

 

[Sultan]

Thanks. I was hoping for a glass bridge (!) but at least it looks like there is a commitment to allowing visibility to the railway itself.