Bridge collapse on M20
Discussion
dandarez said:
Still puzzled why the need for a concrete structure for narrow pedestrian use, and why no central support?
There were lots of RC structures when the motorways were built ... less long term maintenance ... RC construction seems to have been out of fashion for quite some time now ... RC structures are built in situ whereas steel bridges can be fabricated off-site by machines ... maybe due to the demise of experienced tradesmen in the construction industryEdited by ATTAK Z on Saturday 27th August 21:20
Is it possible that the dump truck was loaded on the high part of the trailer above the fifth wheel? And if so assuming it's a 6 ton swivel dump truck it would be about 3m high, how high is the bed on top of the fifth wheel? And even if this was the case it would only have been the roll bar that dislodged the bridge you would have thought it would just bend.
ATTAK Z said:
dandarez said:
Still puzzled why the need for a concrete structure for narrow pedestrian use, and why no central support?
There were lots of RC structures when the motorways were built ... less long term maintenance ... RC construction seems to have been out of fashion for quite some time now ... RC structures are built in situ whereas steel bridges can be fabricated off-site by machines ... maybe due to the demise of experienced tradesmen in the construction industryEdited by ATTAK Z on Saturday 27th August 21:20
ALawson said:
I expect no central support due to "risk" of vehicle collision from 3rd lane, to be honest if it can span why would you put another support in.
The photo of the end of the broken section shows almost a fresh broken concrete colour in the top right section, the other 3/4 looks different.
Exactly right. If a central pier had been constructed it would need to be designed as a highway structure, with impact resistance, vehicle barriers etc. Far better from an engineering and value perspective to avoid it all together. The photo of the end of the broken section shows almost a fresh broken concrete colour in the top right section, the other 3/4 looks different.
The photos showing the joint pre-collapse have a lot of staining so water has evidently been allowed to run through it. The end post-collapse shows some clean concrete, lots of efflorescence where the salts have reacted with the water and some ripped grout / mastic.
It's a true movement joint so there was no mechanical connection between the two halves.
Edited by Elysium on Saturday 27th August 21:32
phil-sti said:
There will be an insurance company having kittens when it returns Tuesday.
I doubt it. They will have it factored into their costs. This is a bridge, and a couple of vehicles - no-one can claim holiday costs, etc - nor are we talking about life long rehabilitation costs for a school bus full of kids.If they haven't factored it in then they are in the wrong business.
Dogwatch said:
General Price said:
It looks like the dumper hit it and got pushed back into the digger.
Certainly looks that way. If the artic had hit the undamaged bridge you would expect the trailer roof to have been scraped back right across whereas on the nearside it is almost complete.Vaud said:
phil-sti said:
There will be an insurance company having kittens when it returns Tuesday.
I doubt it. They will have it factored into their costs. This is a bridge, and a couple of vehicles - no-one can claim holiday costs, etc - nor are we talking about life long rehabilitation costs for a school bus full of kids.If they haven't factored it in then they are in the wrong business.
phil-sti said:
Factored in somebody taking a bridge down? I doubt that's even thought about, bridge strike yes, bringing a bridge down I doubt it
Insurance factors in much worse cases.Life long medical treatment for just one young person is massively higher. I think ~£20M is the highest single person payout that is publicly disclosed.
powerstroke said:
Why was the truck on the hard shoulder ? I would say it was going slowly and the load caught the bottom of the bridge knocking it off ?? the other truck was in lane 1 and going faster hence the damage to its trailer???
I think it was probably queuing for the exit. Lots of people seem to use the hard shoulder for that these days. Looks to me like the dumper truck (on the low loader) has caught under the bridge at low speed. The dumper truck then tilts, lifting the bridge off it's foundation. The forward motion of the truck then moves the bridge a few meters clear and then collapses onto the low loader. There seems to be no clear evidence of an impact big enough to push it off its foundations.
Vaud said:
phil-sti said:
Factored in somebody taking a bridge down? I doubt that's even thought about, bridge strike yes, bringing a bridge down I doubt it
Insurance factors in much worse cases.Life long medical treatment for just one young person is massively higher. I think ~£20M is the highest single person payout that is publicly disclosed.
Elysium said:
powerstroke said:
Why was the truck on the hard shoulder ? I would say it was going slowly and the load caught the bottom of the bridge knocking it off ?? the other truck was in lane 1 and going faster hence the damage to its trailer???
I think it was probably queuing for the exit. Lots of people seem to use the hard shoulder for that these days. Flipatron said:
Looks to me like the dumper truck (on the low loader) has caught under the bridge at low speed. The dumper truck then tilts, lifting the bridge off it's foundation. The forward motion of the truck then moves the bridge a few meters clear and then collapses onto the low loader. There seems to be no clear evidence of an impact big enough to push it off its foundations.
To me it looks like the section of the bridge that collapsed is simply supported by the cantilever sections of the structure ... a common design concept for this type of bridge, which allows for thermal movement (which someone alluded to earlier in the thread) ... as such the supports do not allow for a great deal of lateral loadingGassing Station | News, Politics & Economics | Top of Page | What's New | My Stuff