Bridge collapse on M20

[bobbo89]

dandarez said:

Interesting. The sloping shadow is on the other carriageway, but I see exactly what you mean.

Still puzzled why the need for a concrete structure for narrow pedestrian use, and why no central support?

Concrete because 1960's, cheap and relatively maintenance free
No central support because no central support needed

[mondeoman]

bobbo89 said:

dandarez said:

Interesting. The sloping shadow is on the other carriageway, but I see exactly what you mean.

Still puzzled why the need for a concrete structure for narrow pedestrian use, and why no central support?

Concrete because 1960's, cheap and relatively maintenance free
No central support because no central support needed

Indeed - two independent, self supporting structures either side, connecting piece laid on top. Job done.

[dandarez]

bobbo89 said:

dandarez said:

Interesting. The sloping shadow is on the other carriageway, but I see exactly what you mean.

Still puzzled why the need for a concrete structure for narrow pedestrian use, and why no central support?

Concrete because 1960's, cheap and relatively maintenance free
No central support because no central support needed

Ah, ok. I'm old enough to know (better!). Cheers.

Take it replacement will be ...or repaired? Over to expert advice.

[bobbo89]

It could either be taken down completely whilst a new one is designed and constructed or, they could just replace the collapsed section with a steel structure joined up to the old section. It'll all depend on how much, if any, damage has occurred to the section still standing and whether they just rip that down as part of the tidy up to re-open the motorway.

Alternatively they could just do away with it completely, I'm sure its use will have dropped heavily since it was first built and may now be a bit redundant.

Suspect it could get a bit messy between The HA, insurance companies and the loss adjusters though...

[CAPP0]

bobbo89 said:

Alternatively they could just do away with it completely, I'm sure its use will have dropped heavily since it was first built and may now be a bit redundant.

It joins two sections of a road, East Street, which presumably ran straight through before the motorway was built. No idea why it was built as a pedestrian bridge and not road, but there are a few alternative road crossings in close proximity.

Last time I cycled over there a few months back the northern approach was heavily overgrown and didn't look used much so they may well abandon it I guess.

[Digga]

Doesn't look like that Doosan rubber duck could have hit the bridge - you'd expect a lot of damage to the upper part of the dipper arm from that sort of impact. Unless, perhaps, it was a very low speed. Seems odd though.

Most digger under bridge scenarios end with the machine well and truly wedged underneath.

[saaby93]

Look where the knuckle of that digger has made a nice triangular bend in the bridge fencing
It could look like it's just punted it off its mountings

Or it could be the bridge fell first due to works going on and the digger's run into it



The digger is on the hard shoulder - maybe the clearance height was allowed to be less than standard there

Edited by saaby93 on Saturday 27th August 17:34

[glazbagun]

I cant see how the digger could be sitting nice and square on the bed with little obvious damage to the arm if it had hit the bridge with enough force to move it off.

I'm sure it's chained down, but the force required to knock a bridge from its mountings must surely be enough to knock about a four wheeled digger sitting on a flatbed, no?

That said, theres not much else there that could have done it, certainly not the artic. Would the flatbed ordinarily have been carrying a pole or suchlike which could have caught the underside and lifted the bridge as it passed underneath?

[rolando]

Smollet said:

Obviously a terrorist attack. Thought I'd get in first

I doubt it. More likely Brexit.

Hope the biker makes a speedy recovery.

[chevy55]

My totally uniformed speculation theory. Man was loading digger onto back of low loader, for whatever reason, and as he drove up the ramp the front of the boom hit the bridge knocking it for six. As with most things I am probably wrong but just sayin like.

[saaby93]

glazbagun said:

I cant see how the digger could be sitting nice and square on the bed with little obvious damage to the arm if it had hit the bridge with enough force to move it off.

I'm sure it's chained down, but the force required to knock a bridge from its mountings must surely be enough to knock about a four wheeled digger sitting on a flatbed, no?

That said, theres not much else there that could have done it, certainly not the artic. Would the flatbed ordinarily have been carrying a pole or suchlike which could have caught the underside and lifted the bridge as it passed underneath?

The bridge has broken in half over that white artic so it cant have been that strong

[Beyond Rational]

chevy55 said:

My totally uniformed speculation theory. Man was loading digger onto back of low loader, for whatever reason, and as he drove up the ramp the front of the boom hit the bridge knocking it for six. As with most things I am probably wrong but just sayin like.

And went to the effort of chaining it to the trailer and raising the tail ramps as the dust settled?

[chevy55]

Beyond Rational said:

chevy55 said:

My totally uniformed speculation theory. Man was loading digger onto back of low loader, for whatever reason, and as he drove up the ramp the front of the boom hit the bridge knocking it for six. As with most things I am probably wrong but just sayin like.

And went to the effort of chaining it to the trailer and raising the tail ramps as the dust settled?

He is probably very conscientious and didn't want it to fall off when the st hits the fan

[PF62]

I was amused at the people continuing to drive under the broken half of the bridge - https://twitter.com/Kent_999s/status/7694971328354...

[marksx]

saaby93 said:

The bridge has broken in half over that white artic so it cant have been that strong

Looks to be in the artic, and broken over the flatbed?

[saaby93]

PF62 said:

I was amused at the people continuing to drive under the broken half of the bridge - https://twitter.com/Kent_999s/status/7694971328354...

That piece thats left should be ok, theres less weight on it now the other piece has gone.
It was acting as a support for the missing piece not being supported by the missing piece.
No worries driving under it

[Collectingbrass]

saaby93 said:

glazbagun said:

I cant see how the digger could be sitting nice and square on the bed with little obvious damage to the arm if it had hit the bridge with enough force to move it off.

I'm sure it's chained down, but the force required to knock a bridge from its mountings must surely be enough to knock about a four wheeled digger sitting on a flatbed, no?

That said, theres not much else there that could have done it, certainly not the artic. Would the flatbed ordinarily have been carrying a pole or suchlike which could have caught the underside and lifted the bridge as it passed underneath?

The bridge has broken in half over that white artic so it cant have been that strong

It will have been designed to be supported at each end, on the pier & abutment and the reinforcement will have been designed to cope with the bending stresses to suit that. Once it landed on the HGV, it became supported in the middle, with both ends bending down from the centre support, rather than the ends. That completely changes the bending stresses in the bridge section, with top side being under tension rather than compression. There wont have been any reinforcement to carry those stresses, as they werent expected, and the concrete will have "snapped" as it has no capacity to resist tensile stress.

[saaby93]

marksx said:

saaby93 said:

The bridge has broken in half over that white artic so it cant have been that strong

Looks to be in the artic, and broken over the flatbed?

That yellow thing isn't a massive dumper truck that was up at the front of the flat bed before hitting the bridge?

[marksx]

saaby93 said:

That yellow thing isn't a massive dumper truck that was up at the front of the flat bed before hitting the bridge?

Looks like it. Presumably would have been loaded up front to aid traction?

[turbobloke]

marksx said:

saaby93 said:

The bridge has broken in half over that white artic so it cant have been that strong

Looks to be in the artic, and broken over the flatbed?

Not sure if it's been reported on the thread but news bulletins are now saying that the bridge was hit by a HGV which caused the collapse. Apologies in advance if this is old news.